Febrile Seizure Risk After Vaccination in Children 6 to 23 Months

Safety pharmacology of human endogenous retrovirus-enveloped baculoviral DNA vaccines against SARS-CoV-2 in Sprague-Dawley rats and beagle dogs

The coronavirus disease 2019 (COVID-19) emerged as a major global health crisis, posing significant health, economic, and social challenges. Vaccine development has been a crucial response to the severe-acute-respiratory-syndrome-related coronavirus-2 pandemic owing to the critical role of immunization in controlling infectious diseases, leading to the expedited development of several effective vaccines. Although mRNA platform-based COVID-19 vaccines authorized under emergency-use authorization have been administered globally, concerns regarding the vaccines have increased owing to the occurrence of various side effects. The present study aimed to evaluate the safety of a non-replicating recombinant baculovirus expressing the human endogenous retrovirus envelope gene (AcHERV) vaccine encoding SARS-CoV-2 antigens. Owing to the limited number of existing safety pharmacology studies on AcHERV as a viral vector vaccine, we conducted neurobehavior (Modified Irwin's Test), body temperature, and respiratory function studies in rats and cardiovascular system studies in male beagle dogs, which were administered the AcHERV-COVID-19 vaccine using telemetry. The safety assessment revealed no significant toxicological alterations. However, in rats, both sexes administered with the AcHERV-COVID-19 vaccine exhibited a temporary increase in body temperature, which normalized or showed signs of recovery. In conclusion, AcHERV-COVID-19 demonstrates a sufficient safety profile that supports its potential evaluation in future clinical trials.

Influenza vaccination in older adults and patients with chronic disorders: A position paper from the Portuguese Society of Pulmonology, the Portuguese Society of Cardiology, the Portuguese Society of Diabetology, the Portuguese Society of Infectious Diseases and Clinical Microbiology, the Portuguese Society of Geriatrics and Gerontology, and the Study Group of Geriatrics of the Portuguese Society of Internal Medicine

Influenza affects millions of people worldwide each year and can lead to severe complications, hospitalizations, and even death, especially among vulnerable populations such as older adults and those with chronic medical conditions. Annual vaccination is considered the most effective measure for preventing influenza and its complications. Despite the widespread availability of influenza vaccines, however, vaccination coverage rates remain suboptimal in several countries. Based on the latest scientific evidence and expert opinions on influenza vaccination in older people and patients with chronic disease, the Portuguese Society of Pulmonology (SPP), the Portuguese Society of Diabetology (SPD), the Portuguese Society of Cardiology (SPC), the Portuguese Society of Geriatrics and Gerontology (SPGG), the Study Group of Geriatrics of the Portuguese Society of Internal Medicine (NEGERMI-SPMI), and the Portuguese Society of Infectious Diseases and Clinical Microbiology (SPDIMC) discussed best practices for promoting vaccination uptake and coverage and drew up several recommendations to mitigate the impact of influenza. These recommendations focus on the efficacy and safety of available vaccines; the impact of influenza vaccination on older adults; patients with chronic medical conditions, namely cardiac and respiratory conditions, diabetes, and immunosuppressive diseases; and health care professionals, optimal vaccination timing, and strategies to increase vaccination uptake and coverage. The resulting position paper highlights the critical role that vaccinations play in promoting public health, raising awareness, and encouraging more people to get vaccinated.

Central nervous system manifestations following vaccination against COVID-19

Coronavirus disease 2019 (COVID-19) vaccination has become the most effective countermeasure in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. However, vaccination is associated with side effects. This narrative review focuses on central nervous system (CNS) manifestations following COVID-19 vaccination and provides a summary of the potential underlying mechanisms and methods of diagnosis and management of the vaccination-related CNS manifestations. Headache, myalgia, optic neuritis, seizure, multiple sclerosis, acute disseminated encephalomyelitis and encephalitis, delirium, acute transverse myelitis, and stroke have been reported after COVID-19 vaccination. Constant headache and myalgia are common manifestations that may necessitate further clinical investigation for stroke. To limit consequences, it is imperative to follow standard treatment protocols for each neurological disorder following COVID-19 vaccination. Immunosuppressive medication can be helpful in the treatment of seizures following vaccination since the immune response is involved in their etiology. Clinicians should be aware of the manifestations after COVID-19 vaccination to respond promptly and effectively. Clinical guidelines for the management of CNS manifestations following COVID-19 vaccination are in high demand and would be useful in each new SARS-CoV-2 variant pandemic.

Febrile Seizures: An Updated Narrative Review for Pediatric Ambulatory Care Providers

BACKGROUND

While generally self-limited, febrile seizures result in significant familial distress. Ambulatory pediatric care providers must be prepared to counsel families on the causes, risk factors, management principles, and prognosis of children with febrile seizures.

OBJECTIVE

To provide an updated, evidence-based review of febrile seizures focused on the needs of an ambulatory pediatric care provider.

METHODS

A narrative review of the literature prioritizing landmark articles, metanalyses, longitudinal population longitudinal cohort studies and national level guidelines.

RESULTS

Febrile seizures are aberrant physiological responses to fever in children caused by complex interactions of cytokine mediated neuroinflammation, environmental triggers, and genetic predisposition. Other than investigations to determine fever etiology, routine bloodwork, lumbar punctures, neuroimaging and electroencephalograms are low yield. The general prognosis is excellent, however, clinicians should be aware of long-term outcomes including: cognitive impairment with non-simple febrile seizures; neuropsychiatric associations; recurrent febrile seizure and epilepsy risk factors; and the association between complex febrile seizures and sudden unexpected death. Children with a high risk of recurrence, complex febrile seizures, limited access to care, or extreme parental anxiety may benefit from intermittent oral diazepam prophylaxis.

CONCLUSION

Clinicians should consider four management priorities: 1) terminating the seizure; 2) excluding critical differential diagnoses; 3) investigating fever etiology; and 4) providing adequate counselling to families. The clinical approach and prognosis of febrile seizure can be based on subtype. Children with non-simple (i.e. complex or febrile status epilepticus) febrile seizures require closer care than the vast majority of children with simple febrile seizures, who have excellent outcomes.

Canadian vaccine safety surveillance reports following immunization with seasonal influenza vaccines, 2021-2022

Background

Seasonal influenza vaccines (SIV) authorized for use in Canada have all undergone rigorous regulatory assessments for safety and effectiveness. Serious adverse events following immunization (AEFI) can occur, though they are rare. Continuous safety surveillance of vaccines during the post-marketing phase is a critical component of vaccination programs. This enables the detection of rare, late onset, or unexpected adverse events. An updated safety summary following the introduction of any new vaccines and/or formulations to immunization programs is necessary for refining the risk-benefit profile of a specific vaccine and maintaining public confidence. Here we provide an updated safety summary for SIVs distributed during the 2021/2022 influenza season from AEFI reports submitted to the Canadian Adverse Event Following Immunization Surveillance System (CAEFISS) and the Canadian Vigilance Database (CVD).

Methods

We searched CAEFISS and CVD for individuals who were vaccinated with a SIV between October 1, 2021, and March 31, 2022. Descriptive statistics were calculated, including median age of vaccinated individuals, vaccines co-administered with SIV, and the most frequently reported AEFIs. Crude AEFI reporting rates were calculated by severity of the AEFI report, and SIV-type using doses distributed data. Medical reviews were conducted for reports including death, serious events (or outcomes) after SIV were administered alone, and selected adverse events (i.e., anaphylaxis, Guillain-Barré syndrome, febrile seizures, oculo-respiratory syndrome). Disproportionality analysis was used to identify potential safety signals among SIV and AEFI pairs.

Results

There were 448 AEFI reports, with most AEFI classified as non-serious events (84.2%). The majority of reports described vaccination in adults at least 65 years of age (38.6%). The most frequently reported AEFIs were vaccination site pain, urticaria, pyrexia and rash. Medical review of AEFI reports did not find any evidence that reported deaths were related to vaccination with SIV. Among serious reports, nervous system disorders were the most commonly reported medical conditions. A higher number of events related to vaccination errors were also identified using disproportionality analysis.

Conclusion

Findings from our analysis of reports to CAEFISS and CVD following vaccination with SIV are consistent with the known safety profile of SIVs distributed during the 2021/2022 influenza season. The majority of reports were non-serious with the most common AEFI symptoms occurring at the vaccination site or systemic symptoms that were self-limiting. The majority of vaccination error reports involved the administration of the vaccine at an inappropriate site, although no serious AEFIs were reported.

Recommendations for Prevention and Control of Influenza in Children, 2023-2024

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2023-2024 season. The rationale for the American Academy of Pediatrics recommendation for annual influenza vaccination of all children without medical contraindications starting at 6 months of age is provided. Influenza vaccination is an important strategy for protecting children and the broader community against influenza. This technical report summarizes recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, and vaccination coverage, and provides detailed guidance on vaccine storage, administration, and implementation. The report also provides a brief background on inactivated and live-attenuated influenza vaccines, available vaccines this season, vaccination during pregnancy and breastfeeding, diagnostic testing for influenza, and antiviral medications for treatment and chemoprophylaxis. Strategies to promote vaccine uptake are emphasized.

Combined measles-mumps-rubella-varicella vaccine and febrile convulsions: the risk considered in the broad context

INTRODUCTION

Studies on quadrivalent measles, mumps, rubella, and varicella (MMRV) vaccines have indicated a twofold increased relative risk of febrile convulsion (FC) after the first dose compared to MMR and V administered at the same medical visit (MMR+V).

AREAS COVERED

This narrative review contextualizes FC occurrence after the first MMRV vaccine dose from a clinical perspective and outlines approaches to attenuate FC occurrence post-vaccination.

EXPERT OPINION

While the relative FC risk increases after the first dose of MMRV compared to MMR+V vaccine in measles-naïve infants, the attributable risk is low versus the overall FC risk in the pediatric population triggered by other causes, like natural exposure to pathogens or routine vaccination. No increased risk of FC has been reported after MMRV co-administration with other routine vaccines compared to MMRV alone. Based on our findings and considering the MMRV vaccination benefits (fewer injections, higher coverage, better vaccination compliance), the overall benefit-risk profile of MMRV vaccine is considered to remain positive. Potential occurrence of FC in predisposed children (e.g. with personal/family history of FC) may be attenuated if they receive MMR+V instead of MMRV as the first dose. It is also important to monitor vaccinees for fever during the first 2 weeks post-vaccination.

Recommendations for Prevention and Control of Influenza in Children, 2022-2023

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2022 to 2023 season. The American Academy of Pediatrics recommends annual influenza vaccination of all children without medical contraindications starting at 6 months of age. Influenza vaccination is an important strategy for protecting children and the broader community as well as reducing the overall burden of respiratory illnesses when other viruses, including severe acute respiratory syndrome-coronavirus 2, are cocirculating. This technical report summarizes recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, and vaccination coverage, and provides detailed guidance on storage, administration, and implementation. The report also provides a brief background on inactivated and live attenuated influenza vaccine recommendations, vaccination during pregnancy and breastfeeding, diagnostic testing, and antiviral medications for treatment and chemoprophylaxis. Updated information is provided about the 2021 to 2022 influenza season, influenza immunization rates, the effectiveness of influenza vaccination on hospitalization and mortality, available vaccines, guidance for patients with history of severe allergic reactions to prior influenza vaccinations, and strategies to promote vaccine uptake.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2022-23 Influenza Season

This report updates the 2021–22 recommendations of the Advisory Committee on Immunization Practices (ACIP) concerning the use of seasonal influenza vaccines in the United States

(MMWR Recomm Rep 2021;70[No. RR-5]:1–24). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For each recipient, a licensed and age-appropriate vaccine should be used.With the exception of vaccination for adults aged ≥65 years, ACIP makes no preferential recommendation for a specific vaccine when more than one licensed, recommended, and age-appropriate vaccine is available. All seasonal influenza vaccines expected to be available in the United States for the 2022–23 season are quadrivalent, containing hemagglutinin (HA) derived from one influenza A(H1N1)pdm09 virus, one influenza A(H3N2) virus, one influenza B/Victoria lineage virus, and one influenza B/Yamagata lineage virus. Inactivated influenza vaccines (IIV4s), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4) are expected to be available. Trivalent influenza vaccines are no longer available, but data that involve these vaccines are included for reference.

Influenza vaccines might be available as early as July or August, but for most persons who need only 1 dose of influenza vaccine for the season, vaccination should ideally be offered during September or October. However, vaccination should continue after October and throughout the season as long as influenza viruses are circulating and unexpired vaccine is available. For most adults (particularly adults aged ≥65 years) and for pregnant persons in the first or second trimester, vaccination during July and August should be avoided unless there is concern that vaccination later in the season might not be possible. Certain children aged 6 months through 8 years need 2 doses; these children should receive the first dose as soon as possible after vaccine is available, including during July and August. Vaccination during July and August can be considered for children of any age who need only 1 dose for the season and for pregnant persons who are in the third trimester if vaccine is available during those months

Updates described in this report reflect discussions during public meetings of ACIP that were held on October 20, 2021; January 12, 2022; February 23, 2022; and June 22, 2022. Primary updates to this report include the following three topics: 1) the composition of 2022–23 U.S. seasonal influenza vaccines; 2) updates to the description of influenza vaccines expected to be available for the 2022–23 season, including one influenza vaccine labeling change that occurred after the publication of the 2021–22 ACIP influenza recommendations; and 3) updates to the recommendations concerning vaccination of adults aged ≥65 years. First, the composition of 2022–23 U.S. influenza vaccines includes updates to the influenza A(H3N2) and influenza B/Victoria lineage components. U.S.-licensed influenza vaccines will contain HA derived from an influenza A/Victoria/2570/2019 (H1N1)pdm09-like virus (for egg-based vaccines) or an influenza A/Wisconsin/588/2019 (H1N1)pdm09-like virus (for cell culture–based or recombinant vaccines); an influenza A/Darwin/9/2021 (H3N2)-like virus (for egg-based vaccines) or an influenza A/Darwin/6/2021 (H3N2)-like virus (for cell culture–based or recombinant vaccines); an influenza B/Austria/1359417/2021 (Victoria lineage)-like virus; and an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus. Second, the approved age indication for the cell culture–based inactivated influenza vaccine, Flucelvax Quadrivalent (ccIIV4), was changed in October 2021 from ≥2 years to ≥6 months. Third, recommendations for vaccination of adults aged ≥65 years have been modified. ACIP recommends that adults aged ≥65 years preferentially receive any one of the following higher dose or adjuvanted influenza vaccines: quadrivalent high-dose inactivated influenza vaccine (HD-IIV4), quadrivalent recombinant influenza vaccine (RIV4), or quadrivalent adjuvanted inactivated influenza vaccine (aIIV4). If none of these three vaccines is available at an opportunity for vaccine administration, then any other age-appropriate influenza vaccine should be used

This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2022–23 influenza season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at

https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used according to Food and Drug Administration–licensed indications. Updates and other information are available from CDC’s influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check this site periodically for additional information.

Prevention of pneumococcal infections in childhood: two decades of progress

PURPOSE OF REVIEW

This review highlights progress in combating pediatric pneumococcal disease in the era of pneumococcal conjugate vaccines (PCVs). This review is timely given the development of increased valency PCVs for potential use in children.

RECENT FINDINGS

Countries implementing vaccination programs with PCVs have witnessed dramatic reductions in cases of childhood invasive pneumococcal disease (IPD). In the US, the largest decline of IPD followed the introduction of 7-valent PCV with additional decreases following the switch to 13-valent PCV (PCV13). Despite these gains, IPD still occurs in the US but at much lower rates. Likewise, pneumonia hospitalizations and office visits for otitis media have decreased. Nasopharyngeal colonization with pneumococci has persisted due to replacement by nonvaccine serotypes: colonizing non-PCV13 serotypes have less invasive potential. The PCV era has also been marked by reductions in the proportions of pneumococcus showing nonsusceptibility or resistance to some antimicrobial agents. Furthermore, PCVs have an excellent safety profile.

SUMMARY

Despite proven safety and efficacy, childhood vaccination programs in some countries do not include PCVs, resulting in the majority of global deaths attributable to pneumococcus. Increased worldwide vaccination of children and the development of higher valency vaccines holds additional promise for further reductions in childhood IPD.

Vaccination and childhood epilepsies

INTRODUCTION

The evidence relating vaccination to febrile seizures and epilepsy is evaluated with an emphasis on febrile seizures (FS), Dravet syndrome (DS), West syndrome, and other developmental and epileptic encephalopathies.

METHODS

A systematic literature review using search words vaccination/immunization AND febrile seizures/epilepsy/Dravet/epileptic encephalopathy/developmental encephalopathy was performed. The role of vaccination as the cause/trigger/aggravation factor for FS or epilepsies and preventive measures were analyzed.

RESULTS

From 1428 results, 846 duplicates and 447 irrelevant articles were eliminated; 120 were analyzed.

CONCLUSIONS

There is no evidence that vaccinations cause epilepsy in healthy populations. Vaccinations do not cause epileptic encephalopathies but may be non-specific triggers to seizures in underlying structural or genetic etiologies. The first seizure in DS may be earlier in vaccinated versus non-vaccinated patients, but developmental outcome is similar in both groups. Children with a personal or family history of FS or epilepsy should receive all routine vaccinations. This recommendation includes DS. The known risks of the infectious diseases prevented by immunization are well established. Vaccination should be deferred in case of acute illness. Acellular pertussis DTaP (diphtheria-tetanus-pertussis) is recommended. The combination of certain vaccine types may increase the risk of febrile seizures however the public health benefit of separating immunizations has not been proven. Measles-containing vaccine should be administered at age 12-15 months. Routine prophylactic antipyretics are not indicated, as there is no evidence of decreased FS risk and they can attenuate the antibody response following vaccination. Prophylactic measures (preventive antipyretic medication) are recommended in DS due to the increased risk of prolonged seizures with fever.

Recommendations for Prevention and Control of Influenza in Children, 2021-2022

This technical report accompanies the recommendations of the American Academy of Pediatrics for the routine use of the influenza vaccine and antiviral medications in the prevention and treatment of influenza in children during the 2021-2022 season. Influenza vaccination is an important intervention to protect vulnerable populations and reduce the burden of respiratory illnesses during circulation of severe acute respiratory syndrome coronavirus 2, which is expected to continue during this influenza season. In this technical report, we summarize recent influenza seasons, morbidity and mortality in children, vaccine effectiveness, vaccination coverage, and detailed guidance on storage, administration, and implementation. We also provide background on inactivated and live attenuated influenza vaccine recommendations, vaccination during pregnancy and breastfeeding, diagnostic testing, and antiviral medications for treatment and chemoprophylaxis.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices, United States, 2021-22 Influenza Season

This report updates the 2020-21 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2020;69[No. RR-8]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For each recipient, a licensed and age-appropriate vaccine should be used. ACIP makes no preferential recommendation for a specific vaccine when more than one licensed, recommended, and age-appropriate vaccine is available. During the 2021-22 influenza season, the following types of vaccines are expected to be available: inactivated influenza vaccines (IIV4s), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4).The 2021-22 influenza season is expected to coincide with continued circulation of SARS-CoV-2, the virus that causes COVID-19. Influenza vaccination of persons aged ≥6 months to reduce prevalence of illness caused by influenza will reduce symptoms that might be confused with those of COVID-19. Prevention of and reduction in the severity of influenza illness and reduction of outpatient visits, hospitalizations, and intensive care unit admissions through influenza vaccination also could alleviate stress on the U.S. health care system. Guidance for vaccine planning during the pandemic is available at https://www.cdc.gov/vaccines/pandemic-guidance/index.html. Recommendations for the use of COVID-19 vaccines are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/covid-19.html, and additional clinical guidance is available at https://www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html.Updates described in this report reflect discussions during public meetings of ACIP that were held on October 28, 2020; February 25, 2021; and June 24, 2021. Primary updates to this report include the following six items. First, all seasonal influenza vaccines available in the United States for the 2021-22 season are expected to be quadrivalent. Second, the composition of 2021-22 U.S. influenza vaccines includes updates to the influenza A(H1N1)pdm09 and influenza A(H3N2) components. U.S.-licensed influenza vaccines will contain hemagglutinin derived from an influenza A/Victoria/2570/2019 (H1N1)pdm09-like virus (for egg-based vaccines) or an influenza A/Wisconsin/588/2019 (H1N1)pdm09-like virus (for cell culture-based and recombinant vaccines), an influenza A/Cambodia/e0826360/2020 (H3N2)-like virus, an influenza B/Washington/02/2019 (Victoria lineage)-like virus, and an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus. Third, the approved age indication for the cell culture-based inactivated influenza vaccine, Flucelvax Quadrivalent (ccIIV4), has been expanded from ages ≥4 years to ages ≥2 years. Fourth, discussion of administration of influenza vaccines with other vaccines includes considerations for coadministration of influenza vaccines and COVID-19 vaccines. Providers should also consult current ACIP COVID-19 vaccine recommendations and CDC guidance concerning coadministration of these vaccines with influenza vaccines. Vaccines that are given at the same time should be administered in separate anatomic sites. Fifth, guidance concerning timing of influenza vaccination now states that vaccination soon after vaccine becomes available can be considered for pregnant women in the third trimester. As previously recommended, children who need 2 doses (children aged 6 months through 8 years who have never received influenza vaccine or who have not previously received a lifetime total of ≥2 doses) should receive their first dose as soon as possible after vaccine becomes available to allow the second dose (which must be administered ≥4 weeks later) to be received by the end of October. For nonpregnant adults, vaccination in July and August should be avoided unless there is concern that later vaccination might not be possible. Sixth, contraindications and precautions to the use of ccIIV4 and RIV4 have been modified, specifically with regard to persons with a history of severe allergic reaction (e.g., anaphylaxis) to an influenza vaccine. A history of a severe allergic reaction to a previous dose of any egg-based IIV, LAIV, or RIV of any valency is a precaution to use of ccIIV4. A history of a severe allergic reaction to a previous dose of any egg-based IIV, ccIIV, or LAIV of any valency is a precaution to use of RIV4. Use of ccIIV4 and RIV4 in such instances should occur in an inpatient or outpatient medical setting under supervision of a provider who can recognize and manage a severe allergic reaction; providers can also consider consulting with an allergist to help identify the vaccine component responsible for the reaction. For ccIIV4, history of a severe allergic reaction (e.g., anaphylaxis) to any ccIIV of any valency or any component of ccIIV4 is a contraindication to future use of ccIIV4. For RIV4, history of a severe allergic reaction (e.g., anaphylaxis) to any RIV of any valency or any component of RIV4 is a contraindication to future use of RIV4. This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2021-22 influenza season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used according to Food and Drug Administration-licensed indications. Updates and other information are available from CDC's influenza website (https://www.cdc.gov/flu); vaccination and health care providers should check this site periodically for additional information.

Determining Which of Several Simultaneously Administered Vaccines Increase Risk of an Adverse Event

INTRODUCTION

Childhood immunization schedules often involve multiple vaccinations per visit. When increased risk of an adverse event is observed after simultaneous (same-day) vaccinations, it can be difficult to ascertain which triggered the adverse event. This methods paper discusses a systematic process to determine which of the simultaneously administered vaccine(s) are most likely to have caused an observed increase in risk of an adverse event.

METHODS

We use an example from the literature where excess risk of seizure was observed 1 day after vaccination, but same-day vaccination patterns made it difficult to discern which vaccine(s) may trigger the adverse event. We illustrate the systematic identification process using a simulation that retained the observed pattern of simultaneous vaccination in an empirical cohort of vaccinated children. We simulated "true" effects for diphtheria-tetanus-acellular pertussis (DTaP) and pneumococcal conjugate (PCV) on risk of seizure the day after vaccination. We varied the independent and interactive effects of vaccines (on the multiplicative scale). After applying the process to simulated data, we evaluated risk of seizure 1 day after vaccination in the empirical cohort.

RESULTS

In all simulations, we were able to determine which vaccines contributed to excess risk. In the empirical data, we narrowed the association with seizure from all vaccines in the schedule to three likely candidates, DTaP, PCV, and/or Haemophilus influenzae type B (HiB) (p < 0.01, attributable risk when all three were administered together: five per 100,000). Disentangling their associations with seizure would require a larger sample or more variation in the combinations administered. When none of these three were administered, no excess risk was observed.

CONCLUSION

The process outlined could provide valuable information on the magnitude of potential risk from individual and simultaneousvaccinations. Associations should be further investigated with independent data as well as biologically based, statistically independent hypotheses.

Warp Speed for Coronavirus Disease 2019 (COVID-19) Vaccines: Why Are Children Stuck in Neutral?

While adult clinical trials of coronavirus disease 2019 (COVID-19) vaccines have moved quickly into phase 3 clinical trials, clinical trials have not started in children in the United States. The direct COVID-19 impact upon children is greater than that observed for a number of other pathogens for which we now have effective pediatric vaccines. Additionally, the role of children in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission has clearly been underappreciated. Carefully conducted phase 2 clinical trials can adequately address potential COVID-19 vaccine safety concerns. Delaying phase 2 vaccine clinical trials in children will delay our recovery from COVID-19 and unnecessarily prolong its impact upon children’s education, health, and emotional well-being, and equitable access to opportunities for development and social success. Given the potential direct and indirect benefits of pediatric vaccination, implementation of phase 2 clinical trials for COVID-19 vaccines should begin now.

Safety of vaccines used for routine immunization in the United States: An updated systematic review and meta-analysis

BACKGROUND

Understanding the safety of vaccines is critical to inform decisions about vaccination. Our objective was to conduct a systematic review of the safety of vaccines recommended for children, adults, and pregnant women in the United States.

METHODS

We searched the literature in November 2020 to update a 2014 Agency for Healthcare Research and Quality review by integrating newly available data. Studies of vaccines that used a comparator and reported the presence or absence of key adverse events were eligible. Adhering to Evidence-based Practice Center methodology, we assessed the strength of evidence (SoE) for all evidence statements. The systematic review is registered in PROSPERO (CRD42020180089).

RESULTS

Of 56,603 reviewed citations, 338 studies reported in 518 publications met inclusion criteria. For children, SoE was high for no increased risk of autism following measles, mumps, and rubella (MMR) vaccine. SoE was high for increased risk of febrile seizures with MMR. There was no evidence of increased risk of  intussusception with rotavirus vaccine at the latest follow-up (moderate SoE), nor of diabetes (high SoE). There was no evidence of increased risk or insufficient evidence for key adverse events for newer vaccines such as 9-valent human papillomavirus and meningococcal B vaccines. For adults, there was no evidence of increased risk (varied SoE) or insufficient evidence for key adverse events for the new adjuvanted inactivated influenza vaccine and recombinant adjuvanted zoster vaccine. We found no evidence of increased risk (varied SoE) for key adverse events among pregnant women following tetanus, diphtheria, and acellular pertussis vaccine, including stillbirth (moderate SoE).

CONCLUSIONS

Across a large body of research we found few associations of vaccines and serious key adverse events; however, rare events are challenging to study. Any adverse events should be weighed against the protective benefits that vaccines provide.

Vaccine-Associated Neurological Adverse Events: A Case Report and Literature Review

Vaccination is an effective strategy to reduce the burden of preventable illness. However, many clinical reports revealed that various vaccinations may associate with neurological disorders, mainly including autoimmune disease, febrile seizure, and vaccine-associated paralytic poliomyelitis (VAPP). Although more and more reports revealed that part of the above post-vaccine neurological disorders is not directly related to vaccination, it may be merely a coincidence. However, these reports may increase the hesitancy on vaccination for the public population and influence the coverage of vaccination. In this report, we described a child with acute flaccid paralysis possibly caused by a poliovirus vaccine. To provide feasible ways to realize or reduce the risk of neurological adverse events caused by vaccines, we further provide a mini-review of the literature of vaccination associated with neurological adverse events. This revealed that oral poliomyelitis vaccine use exclusively and type 2 serotype poliomyelitis vaccine virus were the risk factors for VAPP. The combination vaccine was associated with an increased risk of ADEM and FS following immunization when compared with the administration of vaccines separately. Even though cases have been reported that vaccination may be a trigger of anti-NMDARe and GBS, there is no direct evidence to prove that vaccination increased the risk of GBS and anti-NMDARe.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2020-21 Influenza Season

This report updates the 2019–20 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2019;68[No. RR-3]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For each recipient, a licensed and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV4), and live attenuated influenza vaccine (LAIV4) are expected to be available. Most influenza vaccines available for the 2020–21 season will be quadrivalent, with the exception of MF59-adjuvanted IIV, which is expected to be available in both quadrivalent and trivalent formulations.

Updates to the recommendations described in this report reflect discussions during public meetings of ACIP held on October 23, 2019; February 26, 2020; and June 24, 2020. Primary updates to this report include the following two items. First, the composition of 2020–21 U.S. influenza vaccines includes updates to the influenza A(H1N1)pdm09, influenza A(H3N2), and influenza B/Victoria lineage components. Second, recent licensures of two new influenza vaccines, Fluzone High-Dose Quadrivalent and Fluad Quadrivalent, are discussed. Both new vaccines are licensed for persons aged ≥65 years. Additional changes include updated discussion of contraindications and precautions to influenza vaccination and the accompanying Table, updated discussion concerning use of LAIV4 in the setting of influenza antiviral medication use, and updated recommendations concerning vaccination of persons with egg allergy who receive either cell culture–based IIV4 (ccIIV4) or RIV4.

The 2020–21 influenza season will coincide with the continued or recurrent circulation of SARS-CoV-2 (the novel coronavirus associated with coronavirus disease 2019 [COVID-19]). Influenza vaccination of persons aged ≥6 months to reduce prevalence of illness caused by influenza will reduce symptoms that might be confused with those of COVID-19. Prevention of and reduction in the severity of influenza illness and reduction of outpatient illnesses, hospitalizations, and intensive care unit admissions through influenza vaccination also could alleviate stress on the U.S. health care system. Guidance for vaccine planning during the pandemic is available at https://www.cdc.gov/vaccines/pandemic-guidance/index.html.

This report focuses on recommendations for the use of vaccines for the prevention and control of seasonal influenza during the 2020–21 season in the United States. A brief summary of the recommendations and a link to the most recent Background Document containing additional information are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used within Food and Drug Administration (FDA)–licensed indications. Updates and other information are available from CDC’s influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check this site periodically for additional information.

Infant vaccine co-administration: review of 18 years of experience with GSK's hexavalent vaccine co-administered with routine childhood vaccines

INTRODUCTION

The benefits of vaccine co-administration include improved vaccine acceptance and uptake resulting in an increased coverage and protection against multiple childhood diseases, with minimal medical visits. The diphtheria-tetanus-acellular pertussis-hepatitis B-poliomyelitis-Haemophilus influenzae type b vaccine (DTaP-HBV-IPV/Hib) has been available for more than 19 years and is recommended for co-administration with several other infant vaccines.

AREAS COVERED

This is a comprehensive review (34 studies, 21,000 participants) describing the immunogenicity and safety of DTaP-HBV-IPV/Hib when co-administered with 12 different vaccines in infants including pneumococcal, meningococcal, rotavirus or measles-mumps-rubella-varicella.

EXPERT OPINION

Interactions among co-administered vaccines are complex. Therefore, co-administration data are critical before a vaccination regimen can be recommended. Co-administration of DTaP-HBV-IPV/Hib with other routinely administered vaccines was associated with high percentages of children achieving seroprotection/vaccine response against DTaP-HBV-IPV/Hib antigens. In addition, co-administration was not associated with clinically significant interference in immune responses to co-administered vaccines and was well tolerated. Increased systemic reactions observed with some combinations (DTaP-HBV-IPV/Hib + pneumococcal conjugate or meningococcal serogroup B vaccines) were mitigated by prophylactic paracetamol administration. The data reported here, which represent the most frequently used co-administrations of DTaP-HBV-IPV/Hib worldwide, support the concomitant administration of DTaP-HBV-IPV/Hib with other routinely recommended infant vaccines.

Incidence rates of health outcomes of interest among Chinese children exposed to selected vaccines in Yinzhou Electronic Health Records: A population-based retrospective cohort study

INTRODUCTION

Oral poliovirus vaccine (OPV) and diphtheria-tetanus-acellular pertussis vaccine (DTaP) are widely used in China while Haemophilus influenzae type b vaccines (Hib) and a DTaP, inactivated poliovirus (IPV) andHib polysaccharide conjugated to tetanus protein (PRP ~ T) combined vaccine (DTaP-IPV//PRP ~ T) have lower coverage. There are limited safety data on these vaccines in Chinese pediatric populations.

METHODS

To estimate incidence rates (IRs) of health outcomes of interest (HOIs) among children exposed to OPV, DTaP, Hib, and DTaP-IPV//PRP ~ T, we conducted a retrospective cohort study using a population-based electronic health record (EHR) database in Yinzhou district, Ningbo City. Children 0-2 years of age receiving at least one dose of these vaccines between January 1, 2012 and March 31, 2017 were included in the study. Yinzhou EHR database consisted of immunization records and healthcare data of children from hospitals and community health centers in the district. Eight HOIs (i.e., anaphylaxis, febrile seizures, all seizures, asthma, apnea, Kawasaki disease [KD], urticaria/angioedema, Guillain-Barré syndrome [GBS]) were identified using ICD-10 codes.

RESULTS

A total of 220,422 eligible children was identified. No cases of apnea, KD, and GBS were observed within 7 days post-vaccination. During 0-7 days post-vaccination for OPV, DTaP, Hib, and DTaP-IPV//PRP ~ T, the IRs of anaphylaxis, febrile seizures, all seizures, urticaria/angioedema and asthma ranged from 0.0 to 50.0, 0.0 to 99.9, 29.1 to 249.8, 297.8 to 949.1, and 992.7 to 2298.2 per 100,000 person-years, respectively, and 0.0 to 0.9, 0.0 to 1.9, 0.6 to 4.6, 5.6 to 17.5, and 18.7 to 42.3 per 100,000 doses, respectively.

CONCLUSION

IRs of some HOIs in our study were comparable with those in the literature while IRs of other HOIs were not due to differences in study design, post-vaccination risk periods assessed, and vaccine types. Future studies should consider medical chart review for validating HOIs obtained in the EHR.

Timeliness of signal detection for adverse events following influenza vaccination in young children: a simulation case study

OBJECTIVES

To determine how soon after commencement of the seasonal influenza vaccination programme, the AusVaxSafety active vaccine safety surveillance system, currently in use across Australia, would have detected a safety signal had it been operating in 2010 when there was an unprecedented number of febrile seizures in young children associated with one specific influenza vaccine brand, Fluvax (CSL Biotherapies).

DESIGN

Simulation study.

SETTING

Western Australian vaccine influenza coverage and adverse event surveillance data.

OUTCOME MEASURES

Simulated solicited responses from caregivers who would have received an SMS survey about adverse events experienced following seasonal influenza vaccination of their children aged 6 months to <5 years.

PARTICIPANTS

None.

RESULTS

We estimated a >90% probability of a safety signal being detected by AusVaxSafety based on solicited reports for either fever or medical attendance at or before the week ending 28 March 2010, 3 weeks after the start of vaccine distribution. Suspension of the national paediatric influenza vaccination programme as a result of the passive adverse events surveillance operating at the time did not occur until 23 April 2010.

CONCLUSIONS

Active vaccine safety surveillance leading to rapid detection of a safety signal would likely have resulted in earlier suspension of Fluvax from the vaccination programme, prevention of many febrile convulsions and maintenance of public confidence in influenza vaccination for young children.

Fever After Influenza, Diphtheria-Tetanus-Acellular Pertussis, and Pneumococcal Vaccinations

BACKGROUND

Administering inactivated influenza vaccine (IIV), 13-valent pneumococcal conjugate vaccine (PCV13), and diphtheria-tetanus-acellular pertussis (DTaP) vaccine together has been associated with increased risk for febrile seizure after vaccination. We assessed the effect of administering IIV at a separate visit from PCV13 and DTaP on postvaccination fever.

METHODS

In 2017-2018, children aged 12 to 16 months were randomly assigned to receive study vaccines simultaneously or sequentially. They had 2 study visits 2 weeks apart; nonstudy vaccines were permitted at visit 1. The simultaneous group received PCV13, DTaP, and quadrivalent IIV (IIV4) at visit 1 and no vaccines at visit 2. The sequential group received PCV13 and DTaP at visit 1 and IIV4 at visit 2. Participants were monitored for fever (≥38°C) and antipyretic use during the 8 days after visits.

RESULTS

There were 110 children randomly assigned to the simultaneous group and 111 children to the sequential group; 90% received ≥1 nonstudy vaccine at visit 1. Similar proportions of children experienced fever on days 1 to 2 after visits 1 and 2 combined (simultaneous [8.1%] versus sequential [9.3%]; adjusted relative risk = 0.87 [95% confidence interval 0.36-2.10]). During days 1 to 2 after visit 1, more children in the simultaneous group received antipyretics (37.4% vs 22.4%; P = .020).

CONCLUSIONS

In our study, delaying IIV4 administration by 2 weeks in children receiving DTaP and PCV13 did not reduce fever occurrence after vaccination. Reevaluating this strategy to prevent fever using an IIV4 with a different composition in a future influenza season may be considered.

Big Data in the Assessment of Pediatric Medication Safety

Big data (BD) in pediatric medication safety research provides many opportunities to improve the safety and health of children. The number of pediatric medication and device trials has increased in part because of the past 20 years of US legislation requiring and incentivizing study of the effects of medical products in children (Food and Drug Administration Modernization Act of 1997, Pediatric Rule in 1998, Best Pharmaceuticals for Children Act of 2002, and Pediatric Research Equity Act of 2003). There are some limitations of traditional approaches to studying medication safety in children. Randomized clinical trials within the regulatory context may not enroll patients who are representative of the general pediatric population, provide the power to detect rare safety signals, or provide long-term safety data. BD sources may have these capabilities. In recent years, medical records have become digitized, and cell phones and personal devices have proliferated. In this process, the field of biomedical science has progressively used BD from those records coupled with other data sources, both digital and traditional. Additionally, large distributed databases that include pediatric-specific outcome variables are available. A workshop entitled "Advancing the Development of Pediatric Therapeutics: Application of 'Big Data' to Pediatric Safety Studies" held September 18 to 19, 2017, in Silver Spring, Maryland, formed the basis of many of the ideas outlined in this article, which are intended to identify key examples, critical issues, and future directions in this early phase of an anticipated dramatic change in the availability and use of BD.

The risk of febrile seizures following influenza and 13-valent pneumococcal conjugate vaccines

BACKGROUND

Evidence on the risk of febrile seizures after inactivated influenza vaccine (IIV) and 13-valent pneumococcal conjugate vaccine (PCV13) is mixed. In the FDA-sponsored Sentinel Initiative, we examined risk of febrile seizures after IIV and PCV13 in children 6-23 months of age during the 2013-14 and 2014-15 influenza seasons.

METHODS

Using claims data and a self-controlled risk interval design, we compared the febrile seizure rate in a risk interval (0-1 days) versus control interval (14-20 days). In exploratory analyses, we assessed whether the effect of IIV was modified by concomitant PCV13 administration.

RESULTS

Adjusted for age, calendar time and concomitant administration of the other vaccine, the incidence rate ratio (IRR) for risk of febrile seizures following IIV was 1.12 (95% CI 0.80, 1.56) and following PCV13 was 1.80 (95% CI 1.29, 2.52). The attributable risk for febrile seizures following PCV13 ranged from 0.33 to 5.16 per 100,000 doses by week of age. The age and calendar-time adjusted IRR comparing exposed to unexposed time was numerically larger for concomitant IIV and PCV13 (IRR 2.80, 95% CI 1.63, 4.83), as compared to PCV13 without concomitant IIV (IRR 1.54, 95% CI 1.04, 2.28), and the IRR for IIV without concomitant PCV13 suggested no independent effects of IIV (IRR 0.94, 95% CI 0.63, 1.42). Taken together, this suggests a possible interaction between IIV and PCV13, though our study was not sufficiently powered to provide a precise estimate of the interaction.

CONCLUSIONS

We found an elevated risk of febrile seizures after PCV13 vaccine but not after IIV. The risk of febrile seizures after PCV13 is low compared to the overall risk in this population of children, and the risk should be interpreted in the context of the importance of preventing pneumococcal infections.

Challenges in evaluating post-licensure vaccine safety: observations from the Centers for Disease Control and Prevention

Introduction: Vaccination is one of the most successful and cost-effective public health interventions. Although vaccines undergo extensive safety and efficacy evaluations prior to licensure, vaccine safety assessment post-licensure is essential for detecting rare and longer-term adverse events (AEs) and maintaining public confidence in vaccines and recommended immunization programs. Despite the proven effect of vaccines to save lives and prevent disease and overwhelming evidence of vaccines' safety and societal benefit, like any drug, no vaccine can be considered as completely safe and completely effective. New vaccines continue to be introduced and require rapid safety assessment post-licensure through pharmacovigilance reports as well as epidemiologic studies to investigate any potential safety signals.Areas covered: We discuss selected challenges for conducting pharmacovigilance and epidemiologic studies of AEs after vaccination in the United States using the post-licensure safety surveillance infrastructure of the Centers for Disease Control and Prevention (CDC).Expert opinion: The availability of specific post-licensure surveillance systems to monitor and study AEs after vaccination, such as the Vaccine Adverse Event Reporting System, the Vaccine Safety Datalink, and the Clinical Immunization Safety Assessment Project, each with its unique set of strengths and limitations, provide a harmonized and supportive approach to meet several of these barriers.

Recommendations for Prevention and Control of Influenza in Children, 2019-2020

This statement updates the recommendations of the American Academy of Pediatrics for the routine use of influenza vaccines and antiviral medications in the prevention and treatment of influenza in children during the 2019-2020 season. The American Academy of Pediatrics continues to recommend routine influenza immunization of all children without medical contraindications, starting at 6 months of age. Any licensed, recommended, age-appropriate vaccine available can be administered, without preference of one product or formulation over another. Antiviral treatment of influenza with any licensed, recommended, age-appropriate influenza antiviral medication continues to be recommended for children with suspected or confirmed influenza, particularly those who are hospitalized, have severe or progressive disease, or have underlying conditions that increase their risk of complications of influenza.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2019-20 Influenza Season

This report updates the 2018-19 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2018;67[No. RR-3]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. A licensed, recommended, and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV) are expected to be available for the 2019-20 season. Standard-dose, unadjuvanted, inactivated influenza vaccines will be available in quadrivalent formulations (IIV4s). High-dose (HD-IIV3) and adjuvanted (aIIV3) inactivated influenza vaccines will be available in trivalent formulations. Recombinant (RIV4) and live attenuated influenza vaccine (LAIV4) will be available in quadrivalent formulations.Updates to the recommendations described in this report reflect discussions during public meetings of ACIP held on October 25, 2018; February 27, 2019; and June 27, 2019. Primary updates in this report include the following two items. First, 2019-20 U.S. trivalent influenza vaccines will contain hemagglutinin (HA) derived from an A/Brisbane/02/2018 (H1N1)pdm09-like virus, an A/Kansas/14/2017 (H3N2)-like virus, and a B/Colorado/06/2017-like virus (Victoria lineage). Quadrivalent influenza vaccines will contain HA derived from these three viruses, and a B/Phuket/3073/2013-like virus (Yamagata lineage). Second, recent labeling changes for two IIV4s, Afluria Quadrivalent and Fluzone Quadrivalent, are discussed. The age indication for Afluria Quadrivalent has been expanded from ≥5 years to ≥6 months. The dose volume for Afluria Quadrivalent is 0.25 mL for children aged 6 through 35 months and 0.5 mL for all persons aged ≥36 months (≥3 years). The dose volume for Fluzone Quadrivalent for children aged 6 through 35 months, which was previously 0.25 mL, is now either 0.25 mL or 0.5 mL. The dose volume for Fluzone Quadrivalent is 0.5 mL for all persons aged ≥36 months (≥3 years).This report focuses on the recommendations for use of vaccines for the prevention and control of influenza during the 2019-20 season in the United States. A brief summary of these recommendations and a Background Document containing additional information are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to U.S.-licensed influenza vaccines used within Food and Drug Administration-licensed indications. Updates and other information are available from CDC's influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check this site periodically for additional information.

Updates on Influenza Vaccination in Children

Influenza vaccination is recommended for all children 6 months of age and older who do not have contraindications. This article provides an overview of information concerning burden of influenza among children in the United States; US-licensed influenza vaccines; vaccine immunogenicity, effectiveness, and safety; and recent updates relevant to use of these vaccines in pediatric populations. Influenza antiviral medications are discussed. Details concerning vaccine-related topics may be found in the current US Centers for Disease Control and Prevention/Advisory Committee on Immunization Practices recommendations for use of influenza vaccines (https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html). Additional information on influenza antivirals is located at https://www.cdc.gov/flu/professionals/antivirals/index.htm.

Similar relative risks of seizures following measles containing vaccination in children born preterm compared to full-term without previous seizures or seizure-related disorders

BACKGROUND

Febrile seizures are associated with the first dose of measles-containing vaccines and the risk increases with chronologic age during the second year of life. We used the Vaccine Safety Datalink (VSD) to determine if the relative increase in risk of seizures following receipt of measles-containing vaccine differs by gestational age at birth.

METHODS

Children were eligible if they received their first dose of measles-containing vaccine at age 12 through 23 months from January 2003 through September 2015. Children were excluded if they had a history of seizure or conditions strongly related to seizure prior to 12 months of age. Seizures were identified by diagnostic codes in the inpatient or emergency department settings. Using risk-interval analysis, we estimated the incidence rate ratio (IRR) for seizures in the 7 through 10 days (risk period) vs 15 through 42 days (control period) following receipt of measles-containing vaccines in children born preterm (<37 weeks gestation age) and those born full-term (≥37 weeks).

RESULTS

There were 532,375 children (45,343 preterm and 487,032 full-term) who received their first dose of measles-containing vaccine at age 12 through 23 months. The IRRs of febrile seizures 7 through 10 days compared with 15 through 42 days after receipt of measles-containing vaccine were 3.9 (95% CI: 2.5-6.0) in preterm children and 3.2 (2.7-3.7) in full-term children; the ratio of IRRs: was 1.2 (0.76-1.9), p = 0.41. IRRs were also similar across gestational age groups, by vaccine type received (measles-mumps-rubella [MMR] or measles-mumps-rubella-varicella [MMRV]) and age at vaccination (12-15 or 16-23 months).

CONCLUSION

Vaccination with a measles-containing vaccine in the second year of life is associated with a similar relative risk of a first seizure in children born preterm as in those who were born full-term.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices-United States, 2018-19 Influenza Season

This report updates the 2017-18 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines in the United States (MMWR Recomm Rep 2017;66[No. RR-2]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. A licensed, recommended, and age-appropriate vaccine should be used. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV) are expected to be available for the 2018-19 season. Standard-dose, unadjuvanted, inactivated influenza vaccines will be available in quadrivalent (IIV4) and trivalent (IIV3) formulations. Recombinant influenza vaccine (RIV4) and live attenuated influenza vaccine (LAIV4) will be available in quadrivalent formulations. High-dose inactivated influenza vaccine (HD-IIV3) and adjuvanted inactivated influenza vaccine (aIIV3) will be available in trivalent formulations.Updates to the recommendations described in this report reflect discussions during public meetings of ACIP held on October 25, 2017; February 21, 2018; and June 20, 2018. New and updated information in this report includes the following four items. First, vaccine viruses included in the 2018-19 U.S. trivalent influenza vaccines will be an A/Michigan/45/2015 (H1N1)pdm09-like virus, an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus, and a B/Colorado/06/2017-like virus (Victoria lineage). Quadrivalent influenza vaccines will contain these three viruses and an additional influenza B vaccine virus, a B/Phuket/3073/2013-like virus (Yamagata lineage). Second, recommendations for the use of LAIV4 (FluMist Quadrivalent) have been updated. Following two seasons (2016-17 and 2017-18) during which ACIP recommended that LAIV4 not be used, for the 2018-19 season, vaccination providers may choose to administer any licensed, age-appropriate influenza vaccine (IIV, RIV4, or LAIV4). LAIV4 is an option for those for whom it is appropriate. Third, persons with a history of egg allergy of any severity may receive any licensed, recommended, and age-appropriate influenza vaccine (IIV, RIV4, or LAIV4). Additional recommendations concerning vaccination of egg-allergic persons are discussed. Finally, information on recent licensures and labeling changes is discussed, including expansion of the age indication for Afluria Quadrivalent (IIV4) from ≥18 years to ≥5 years and expansion of the age indication for Fluarix Quadrivalent (IIV4), previously licensed for ≥3 years, to ≥6 months.This report focuses on the recommendations for use of vaccines for the prevention and control of influenza during the 2018-19 season in the United States. A Background Document containing further information and a brief summary of these recommendations are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html.These recommendations apply to U.S.-licensed influenza vaccines used within Food and Drug Administration-licensed indications. Updates and other information are available at CDC's influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check CDC's influenza website periodically for additional information.

Febrile seizures: an overview

Background

Febrile seizures are the most common neurologic disorder in childhood. Physicians should be familiar with the proper evaluation and management of this common condition.

Objective

To provide an update on the current understanding, evaluation, and management of febrile seizures.

Methods

A PubMed search was completed in Clinical Queries using the key terms ‘febrile convulsions’ and ‘febrile seizures’. The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews.

Results

Febrile seizures, with a peak incidence between 12 and 18 months of age, likely result from a vulnerability of the developing central nervous system to the effects of fever, in combination with an underlying genetic predisposition and environmental factors. The majority of febrile seizures occur within 24 hours of the onset of the fever. Febrile seizures can be simple or complex. Clinical judgment based on variable presentations must direct the diagnostic studies which are usually not necessary in the majority of cases. A lumbar puncture should be considered in children younger than 12 months of age or with suspected meningitis. Children with complex febrile seizures are at risk of subsequent epilepsy. Approximately 30–40% of children with a febrile seizure will have a recurrence during early childhood. The prognosis is favorable as the condition is usually benign and self-limiting. Intervention to stop the seizure often is unnecessary.

Conclusion

Continuous preventative antiepileptic therapy for the prevention of recurrent febrile seizures is not recommended. The use of intermittent anticonvulsant therapy is not routinely indicated. Antipyretics have no role in the prevention of febrile seizures.

Prevention of Pertussis, Tetanus, and Diphtheria with Vaccines in the United States: Recommendations of the Advisory Committee on Immunization Practices (ACIP)

This report compiles and summarizes all recommendations from CDC's Advisory Committee on Immunization Practices (ACIP) regarding prevention and control of tetanus, diphtheria, and pertussis in the United States. As a comprehensive summary of previously published recommendations, this report does not contain any new recommendations and replaces all previously published reports and policy notes; it is intended for use by clinicians and public health providers as a resource. ACIP recommends routine vaccination for tetanus, diphtheria, and pertussis. Infants and young children are recommended to receive a 5-dose series of diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccines, with one adolescent booster dose of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine. Adults who have never received Tdap also are recommended to receive a booster dose of Tdap. Women are recommended to receive a dose of Tdap during each pregnancy, which should be administered from 27 through 36 weeks' gestation, regardless of previous receipt of Tdap. After receipt of Tdap, adolescents and adults are recommended to receive a booster tetanus and diphtheria toxoids (Td) vaccine every 10 years to assure ongoing protection against tetanus and diphtheria.

Safety study of live, oral human rotavirus vaccine: A cohort study in United States health insurance plans

As part of a regulatory commitment for post-licensure safety monitoring of live, oral human rotavirus vaccine (RV1), this study compared the incidence rates (IR) of intussusception, acute lower respiratory tract infection (LRTI) hospitalization, Kawasaki disease, convulsion, and mortality in RV1 recipients versus inactivated poliovirus vaccine (IPV) recipients in concurrent (cIPV) and recent historical (hIPV) comparison cohorts. Vaccine recipients were identified in 2 claims databases from August 2008 – June 2013 (RV1 and cIPV) and January 2004 – July 2008 (hIPV). Outcomes were identified in the 0–59 days following the first 2 vaccine doses. Intussusception, Kawasaki disease, and convulsion were confirmed via medical record review. Outcome IRs were estimated. Incidence rate ratios (IRRs) were obtained from Poisson regression models. A post-hoc self-controlled case series (SCCS) analysis compared convulsion IRs in a 0–7 day post-vaccination period to a 15–30 day post-vaccination period. We identified 57,931 RV1, 173,384 cIPV, and 159,344 hIPV recipients. No increased risks for intussusception, LRTI, Kawasaki disease, or mortality were observed. The convulsion IRRs were elevated following RV1 Dose 1 (cIPV: 2.07, 95% confidence interval [CI]: 1.27 – 3.38; hIPV: 2.05, 95% CI: 1.24 – 3.38), a finding which is inconclusive as it was observed in only one of the claims databases. The IRR following RV1 Dose 1 in the SCCS analysis lacked precision (2.40, 95% CI: 0.73 – 7.86). No increased convulsion risk was observed following RV1 Dose 2. Overall, this study supports the favorable safety profile of RV1. Continued monitoring for safety signals through routine surveillance is needed to ensure vaccine safety.

Epilepsy in Children After Pandemic Influenza Vaccination

OBJECTIVES

To determine if pandemic influenza vaccination was associated with an increased risk of epilepsy in children.

METHODS

Information from Norwegian registries from 2006 through 2014 on all children <18 years living in Norway on October 1, 2009 was used in Cox regression models to estimate hazard ratios for incident epilepsy after vaccination. A self-controlled case series analysis was used to estimate incidence rate ratios in defined risk periods after pandemic vaccination.

RESULTS

In Norway, the main period of the influenza A subtype H1N1 pandemic was from October 2009 to December 2009. On October 1, 2009, 1 154 113 children <18 years of age were registered as residents in Norway. Of these, 572 875 (50.7%) were vaccinated against pandemic influenza. From October 2009 through 2014 there were 3628 new cases of epilepsy (incidence rate 6.09 per 10 000 person-years). The risk of epilepsy was not increased after vaccination: hazard ratio: 1.07; 95% confidence interval: 0.94-1.23. Results from the self-controlled case series analysis supported the finding of no association between vaccination and subsequent epilepsy.

CONCLUSIONS

Pandemic influenza vaccination was not associated with increased risk of epilepsy. Concerns about pandemic vaccination causing epilepsy in children seem to be unwarranted.

Methods for addressing "innocent bystanders" when evaluating safety of concomitant vaccines

PURPOSE

The need to develop methods for studying the safety of childhood immunization schedules has been recognized by the Institute of Medicine and Department of Health and Human Services. The recommended childhood immunization schedule includes multiple vaccines in a visit. A key concern is safety of concomitant (same day) versus separate day vaccination. This paper addresses a methodological challenge for observational studies using a self-controlled design to investigate the safety of concomitant vaccination.

METHODS

We propose a process for distinguishing which of several concomitantly administered vaccines is responsible for increased risk of an adverse event while adjusting for confounding due to relationships between effect modifying risk factors and concomitant vaccine combinations. We illustrate the approach by re-examining the known increase in risk of seizure 7 to 10 days after measles-mumps-rubella (MMR) vaccination and evaluating potential independent or modifying effects of other vaccines.

RESULTS

Initial analyses suggested that DTaP had both an independent and potentiating effect on seizure. After accounting for the relationship between age at vaccination and vaccine combination, there was little evidence for increased risk of seizure with same day administration of DTaP and MMR; incidence rate ratio, 95% confidence interval 1.2 (0.9-1.6), P value = θ.226.

CONCLUSION

We have shown that when using a self-controlled design to investigate safety of concomitant vaccination, it can be critically important to adjust for time-invariant effect modifying risk factors, such as age at time of vaccination, which are structurally related to vaccination patterns due to recommended immunization schedules.

Development and application of two semi-automated tools for targeted medical product surveillance in a distributed data network

PURPOSE OF REVIEW

An important component of the Food and Drug Administration's Sentinel Initiative is the active post-market risk identification and analysis (ARIA) system, which utilizes semi-automated, parameterized computer programs to implement propensity-score adjusted and self-controlled risk interval designs to conduct targeted surveillance of medical products in the Sentinel Distributed Database. In this manuscript, we review literature relevant to the development of these programs and describe their application within the Sentinel Initiative.

RECENT FINDINGS

These quality-checked and publicly available tools have been successfully used to conduct rapid, replicable, and targeted safety analyses of several medical products. In addition to speed and reproducibility, use of semi-automated tools allows investigators to focus on decisions regarding key methodological parameters. We also identified challenges associated with the use of these methods in distributed and prospective datasets like the Sentinel Distributed Database, namely uncertainty regarding the optimal approach to estimating propensity scores in dynamic data among data partners of heterogeneous size.

SUMMARY

Future research should focus on the methodological challenges raised by these applications as well as developing new modular programs for targeted surveillance of medical products.

Prognostic factors for epilepsy following first febrile seizure in Saudi children

BACKGROUND

Febrile seizure is the most common convulsive event during childhood, but it is generally considered benign.

OBJECTIVES

To estimate the rate of epilepsy after first presentation of febrile seizure and to describe factors that can predispose children to have subsequent epilepsy after their first febrile seizure.

DESIGN

Retrospective chart review.

SETTING

A tertiary care center in Riyadh.

PATIENTS AND METHODS

All children whose first febrile seizure developed between 2009-2012, and who were admitted to the pediatric wards.

MAIN OUTCOME MEASURES

The rate of epilepsy and prognostic factors for epilepsy following first febrile seizure.

RESULTS

Of 109 febrile seizure patients, 6 (5.5%, 95% CI: 2.1% - 11.6%) were diagnosed with subsequent epilepsy 5 to 46 months after their first febrile seizure. The risk of having subsequent epilepsy was higher in children who were convulsing at a low-grade fever during their first febrile convulsion (P=.02). Moreover, delayed vaccination status (P=.03), prolonged duration of the first convulsion (P=.04), frequent febrile seizures (P=.01), and fever without documented infection (P=.03) during the first febrile convulsion were associated with epilepsy.

CONCLUSION

The rate of epilepsy following first febrile seizure in Saudi children is within the range of values reported in different populations. Although most childhood febrile seizures are self-limiting, careful observation is needed, particularly for children who exhibit factors associated with epilepsy.

LIMITATIONS

Conducted at a single center in Saudi Arabia, which may limit generalizability.

Febrile Seizure Risk after Vaccination in Children One to Five Months of Age

BACKGROUND

The risk of febrile seizure is temporarily increased for a few days after the administration of certain vaccines in children aged six to 23 months. Our objective was to determine the febrile seizure risk following vaccination in children aged one to five months, when six different vaccines are typically administered.

METHODS

We identified emergency department visits and inpatient admissions with International Classification of Diseases, Ninth Revision, febrile seizure codes among children enrolled in nine Vaccine Safety Datalink participating health care organizations from 2006 through 2011. Febrile seizures were confirmed by medical record abstraction. We used the self-controlled risk-interval method to compare the incidence of febrile seizure during postvaccination days 0 to 1 (risk interval) versus days 14 to 20 (control interval).

RESULTS

We identified 15 febrile seizure cases that occurred after 585,342 vaccination visits. The case patients were aged three to five months. The patients had received a median of four (range two to six) vaccines simultaneously. The incidence rate ratio of febrile seizure after vaccination was 23 (95% confidence interval 5.13 to 100.8), and the attributable risk was 3.92 (95% confidence interval 1.68 to 6.17) febrile seizure cases per 100,000 persons vaccinated.

CONCLUSIONS

Vaccination in children aged three to five months was associated with a large relative risk of febrile seizure on the day of and the day after vaccination, but the risk was small in absolute terms. Postvaccination febrile seizure should not be a concern for the vast majority of children receiving vaccines, but clinicians might take this risk into consideration when evaluating and treating children susceptible to seizures precipitated by fever.

The effect of antipyretics on immune response and fever following receipt of inactivated influenza vaccine in young children

BACKGROUND

Antipyretics reduce fever following childhood vaccinations; after inactivated influenza vaccine (IIV) they might ameliorate fever and thereby decrease febrile seizure risk, but also possibly blunt the immune response. We assessed the effect of antipyretics on immune responses and fever following IIV in children ages 6 through 47 months.

METHODS

Over the course of three seasons, one hundred forty-two children, receiving either a single or the first of 2 recommended doses of IIV, were randomized to receive either oral acetaminophen suspension (n = 59) or placebo (n = 59) (double-blinded) or ibuprofen (n = 24) (open-label) immediately following IIV and every 4-8 h thereafter for 24 h. Blood samples were obtained at enrollment and 4 weeks following the last recommended IIV dose. Responses to IIV were assessed by hemagglutination inhibition assay (HAI). Seroprotection was defined as an HAI titer ≥1:40 and seroconversion as a titer ≥1:40 if baseline titer <1:10 or four-fold rise if baseline titer ≥1:10. Participants were monitored for fever and other solicited symptoms on the day of and day following IIV.

RESULTS

Significant differences in seroconversion and post-vaccination seroprotection were not observed between children included in the different antipyretic groups and the placebo group for the vaccine antigens included in IIV over the course of the studies. Frequencies of solicited symptoms, including fever, were similar between treatment groups and the placebo group.

CONCLUSIONS

Significant blunting of the immune response was not observed when antipyretics were administered to young children receiving IIV. Studies with larger sample sizes are needed to definitively establish the effect of antipyretics on IIV immunogenicity.

Administering Multiple Injectable Vaccines During a Single Visit-Summary of Findings From the Accelerated Introduction of Inactivated Polio Vaccine Globally

Background.

In 2013, the World Health Organization’s (WHO’s) Strategic Advisory Group of Experts (SAGE) recommended that all 126 countries using only oral polio vaccine (OPV) introduce at least 1 dose of inactivated polio vaccine (IPV) into their routine immunization schedules by the end of 2015. In many countries, the addition of IPV would necessitate delivery of multiple injectable vaccines (hereafter, “multiple injections”) during a single visit, with infants receiving IPV alongside pentavalent vaccine (which covers diphtheria, tetanus, and whole-cell pertussis; hepatitis B; and Haemophilus influenzae type b) and pneumococcal vaccine. Unanticipated concerns emerged from countries over acceptability of multiple injections, sites of administration, and safety. We contextualized the issues surrounding multiple injections by documenting concerns associated with administration of ≥3 injections, existing evidence in the published literature, and findings of a systematic review on administration practices and techniques.

Methods.

Concerns associated with multiple-injection visits were documented from meetings and personal communications with immunization program managers. Published literature on the acceptability of multiple injections by providers and caregivers was summarized, and a systematic review of the literature on administration practices was completed on the following topics: spacing between injection sites (ie, vaccine spacing), site of injection, route of injection, and procedural preparedness. WHO and United Nations Children’s Fund data from 2013–2015 were used to assess multiple-injection visits included in national immunization schedules.

Results.

Healthcare provider and caregiver attitudes and practices indicated concerns about infant pain, potential adverse effects, and uncertainty about vaccine effectiveness with multiple-injection visits. Published literature reinforced the record of safety and acceptance of the recommended schedule of IPV by the SAGE, but the evidence was largely from developed countries. Parental acceptance of multiple injections was associated with a positive provider recommendation to the caregiver. Findings of the systematic review identified that the intramuscular route is preferred over the subcutaneous route for vaccine administration and that the vastus lateralis muscle is preferred over the deltoid muscle for intramuscular injections. Recommendations on vaccine spacing and procedural preparedness were based on practical necessities, but comparative evidence was not identified. During 2013–2015, 85 countries added IPV to their immunization schedules, 46 (55%) of which adopted a schedule resulting in 3 injectable vaccines being administered in a single visit.

Conclusion.

The multiple-injection experience identified gaps in guidance for future vaccine introductions. Global partner organizations quickly mobilized to assess, document, and communicate the existing global experience on multiple-injection visits. This evidence-based approach provided reassurance to opinion leaders, health workers, and professional societies, thus encouraging uptake of IPV as a second or third injection in an accelerated manner globally.

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices - United States, 2017-18 Influenza Season

This report updates the 2016-17 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines (MMWR Recomm Rep 2016;65[No. RR-5]). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. A licensed, recommended, and age-appropriate vaccine should be used.For the 2017-18 season, quadrivalent and trivalent influenza vaccines will be available. Inactivated influenza vaccines (IIVs) will be available in trivalent (IIV3) and quadrivalent (IIV4) formulations. Recombinant influenza vaccine (RIV) will be available in trivalent (RIV3) and quadrivalent (RIV4) formulations. Live attenuated influenza vaccine (LAIV4) is not recommended for use during the 2017-18 season due to concerns about its effectiveness against (H1N1)pdm09 viruses during the 2013-14 and 2015-16 seasons. Recommendations for different vaccine types and specific populations are discussed. No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended product is available.Updates to the recommendations described in this report reflect discussions during public meetings of ACIP held on October 20, 2016; February 22, 2017; and June 21, 2017. New and updated information in this report includes the following:•Vaccine viruses included in the 2017-18 U.S. trivalent influenza vaccines will be an A/Michigan/45/2015 (H1N1)pdm09-like virus, an A/Hong Kong/4801/2014 (H3N2)-like virus, and a B/Brisbane/60/2008-like virus (Victoria lineage). Quadrivalent influenza vaccines will contain these three viruses and an additional influenza B vaccine virus, a B/Phuket/3073/2013-like virus (Yamagata lineage).• Information on recent licensures and labelling changes is discussed, including licensure of Afluria Quadrivalent (IIV4; Seqirus, Parkville, Victoria, Australia); Flublok Quadrivalent (RIV4; Protein Sciences, Meriden, Connecticut); and expansion of the age indication for FluLaval Quadrivalent (IIV4; ID Biomedical Corporation of Quebec, Quebec City, Quebec, Canada), previously licensed for ≥3 years, to ≥6 months.• Pregnant women may receive any licensed, recommended, age-appropriate influenza vaccine.• Afluria (IIV3; Seqirus, Parkville, Victoria, Australia) may be used for persons aged ≥5 years, consistent with Food and Drug Administration-approved labeling.• FluMist Quadrivalent (LAIV4; MedImmune, Gaithersburg, Maryland) should not be used during the 2017-18 season due to concerns about its effectiveness against influenza A(H1N1)pdm09 viruses in the United States during the 2013-14 and 2015-16 influenza seasons.This report focuses on the recommendations for use of vaccines for the prevention and control of influenza during the 2017-18 season in the United States. A Background Document containing further information and a summary of these recommendations are available at https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html. These recommendations apply to licensed influenza vaccines used within Food and Drug Administration-licensed indications, including those licensed after the publication date of this report. Updates and other information are available at CDC's influenza website (https://www.cdc.gov/flu). Vaccination and health care providers should check CDC's influenza website periodically for additional information.

Influenza in children

PURPOSE OF REVIEW

We review the current information and evidence available on the global burden of disease in the pediatric population, clinical presentation and complications, testing, treatment, and immunization.

RECENT FINDINGS

In addition to multiple other risk factors for influenza complications, children with neurologic and neuromuscular disorders are significantly higher risk for serious complications. In practice, there is no lower age limit for children with influenza who can be treated with oseltamivir. The quadrivalent live attenuated influenza vaccine was not recommended for use during the 2016-2017 season due to poor effectiveness.

SUMMARY

Influenza infection causes a significant burden of disease each year in the pediatric population worldwide. Both healthy and chronically ill children can fall prey to complications either due to the virus itself or secondary bacterial infection. Children within high-risk groups should be tested and treated with neuraminidase inhibitors. Immunization against influenza is well tolerated and effective.

Prophylactic antipyretics for prevention of febrile seizures following vaccination

Question Parents of a 12-month-old boy are bringing their son in to my family practice clinic for his well-baby visit. As the infant is due for his 12-month vaccine series, the parents are concerned after hearing about the association between certain vaccinations and an increased risk of febrile seizures, and are wondering if they should administer prophylactic antipyretics to decrease the risk of febrile seizure. What vaccinations are associated with increased risk of febrile seizure, and is there evidence supporting prophylactic administration of antipyretics to prevent febrile seizures? Answer Vaccinations associated with increased risk of febrile seizure include the following: the measles-mumps-rubella vaccine; the measles-mumps-rubella-varicella vaccine; the combined diphtheria, tetanus, acellular pertussis, polio, and Haemophilus influenzae type b vaccine; the whole-cell pertussis vaccine; the 7-valent pneumococcal conjugate vaccine; and concomitant administration of the trivalent inactivated influenza vaccine with either the 7-valent pneumococcal conjugate vaccine or the diphtheria, tetanus, and acellular pertussis vaccine. Despite being a higher-risk group, children receiving these vaccinations should not receive prophylactic antipyretics, as no statistically significant reduction in the rate of febrile seizures has been documented, and prophylactic antipyretic use potentially decreases the immune response to certain vaccines.

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Question Les parents d’un petit garçon de 12 mois accompagnent leur fils à ma pratique familiale pour sa visite de puériculture. Comme l’enfant est dû pour sa série vaccinale de 12 mois, les parents s’inquiètent parce qu’ils ont entendu parler d’un lien entre certains vaccins et un risque accru de convulsions fébriles, et ils se demandent s’ils devraient administrer un antipyrétique en prophylaxie pour réduire le risque. Quels vaccins sont liés à un risque accru de convulsions fébriles, et existe-t-il des données à l’appui des antipyrétiques pour prévenir les convulsions fébriles?

Réponse Les vaccins liés à un risque accru de convulsions fébriles sont les suivants : vaccin contre la rougeole, les oreillons et la rubéole; vaccin contre la rougeole, les oreillons, la rubéole et la varicelle; combinaison du vaccin contre la diphtérie, le tétanos, la coqueluche acellulaire et la polio et du vaccin contre le virus Haemophilus influenzae de type B; vaccin contre la coqueluche à germes entiers; vaccin conjugué 7-valent contre le pneumocoque; et administration concomitante du vaccin antigrippal trivalent inactivé avec soit le vaccin conjugué 7-valent contre le pneumocoque, soit le vaccin contre la diphtérie, le tétanos et la coqueluche acellulaire. Malgré le fait qu’ils font partie d’un groupe à risque élevé, les enfants qui reçoivent ces vaccins ne doivent pas prendre d’antipyrétiques en prophylaxie, puisque aucune réduction significative du taux de convulsions fébriles n’a été rapportée, et que les antipyrétiques en prophylaxie réduisent potentiellement la réponse immunitaire à certains vaccins.