Safety and tolerability of cold-adapted influenza vaccine, trivalent, in infants younger than 6 months of age

Safety and Viral Shedding of Live Attenuated Influenza Vaccine (LAIV) in Chinese Healthy Juveniles and Adults: A Phase Ⅰ Randomized, Double-Blind, Placebo-Controlled Study

This study was a randomized, double-blind, placebo-controlled study to evaluate the safety and viral shedding of live attenuated influenza vaccine (LAIV) in Chinese healthy juveniles and adults. A total of 80 Eligible volunteers were divided into two age groups (≥18 and 3–17 years old). Volunteers were randomly and equally assigned to the experimental group and placebo-controlled group by ratio of 3:1 in each age group. Vaccination was carried out in steps. Totally, 34 (56.67%) adverse events and 24 (40.00%) adverse reactions of the LAIV group were reported. Most adverse reactions were grade 1 and grade 2, and the incidence of adverse reactions that grade 3 was 5%. The most common local reaction was runny nose/nasal congestion (n = 4, 6.67%). And the most common general reaction was fever (n = 10, 16.67%). There were no statistically significant differences in the incidence of total adverse reactions, different grades of adverse reactions, and symptoms between the experimental group and placebo-controlled group. No severe adverse events were reported. Three subjects (5.00%) had been detected vaccine strains on the 3rd day after LAIV vaccination; one was type B and the other two were H3N2. Four subjects (6.67%) had been detected with vaccine strains on the 7th day after LAIV vaccination, all were H3N2. There were no subjects detected carrying the influenza virus on the 15th day after vaccination. There were no statistically significant differences in the positive rate of vaccine strains of influenza virus between the experimental group and placebo-controlled group. The vaccine was well tolerated and not associated with increased rates in adverse reactions or the occurrence of severe adverse events. Pathogenicity of shed vaccine virus to surrounding people was not observed. Thus, Phase Ⅱ study can be carried out as scheduled.

Safety and Efficacy of Spray Intranasal Live Attenuated Influenza Vaccine: Systematic Review and Meta-Analysis

Although influenza is a major public health concern, little is known about the use of spray live attenuated influenza vaccine (LAIV) among adults. For this reason, we conducted a systematic review and meta-analysis to investigate the efficacy and safety of LAIV, especially in adults with/without clinical conditions and children <2 years, with the final aim of possibly extending the clinical indications. PubMed/MEDLINE and Scopus were the two databases consulted through February 2021. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. A critical appraisal was conducted. Analyses were performed by using ProMeta3 software. Twenty-two studies were included, showing that LAIV was associated with a higher probability of seroconversion when compared with a placebo and considering the A/H1N1 serotype (pooled OR = 2.26 (95% CI = 1.12–4.54), p-value = 0.022; based on 488 participants, without heterogeneity (I2 = 0.0%)). The meta-analysis also confirmed no significant association with systemic adverse events. Only rhinorrhea, nasal congestion, and sore throat were significantly associated with LAIV compared to the placebo. Despite limited available evidence, LAIV has proved to be a safe and effective flu vaccination, also due to its very low invasiveness, and our review’s results can be considered a starting point for guiding future research and shaping forthcoming vaccination campaigns.

Influenza Vaccines Delivered in Early Childhood Could Turn Antigenic Sin into Antigenic Blessings

Substantial evidence has accumulated that "original antigenic sin" is a central factor shaping immune responses against influenza viruses. Here, we argue that this propensity of initial influenza virus exposure to establish a lifelong immunological imprint presents a remarkable opportunity: Immunization of infants prior to their initial, natural viral exposure could circumvent narrow immunological imprinting directed toward a single viral strain. Simultaneous initial exposure to antigens from multiple influenza strains via vaccination holds the promise of extending immunological imprinting across all currently circulating strains and against potential pandemic strains of influenza A virus, potentially providing a readily accessible form of universal protection against severe disease from both pandemic and seasonal influenza.

Neonatal vaccine effectiveness and the role of adjuvants

Introduction: Neonates are less responsive to vaccines than adults, making it harder to protect newborns against infection. Neonatal differences in antigen-presenting cell, B and T cell function, all likely contribute. A key question is whether novel adjuvants might be able to make neonatal vaccines more effective. Areas covered: This review addresses the issues of how to improve neonatal vaccines, which we have defined as vaccines given in the first 4 weeks of life in a human infant or the first week of life in a mouse. A search was performed using keywords including 'neonatal immunity', 'neonatal immunisation', 'vaccine' and 'adjuvant' of PubMed articles published between 1960 and 2018. Expert opinion: Sugar-like structures have recently been shown to prime the infant adaptive immune system to respond to vaccines, being potentially more effective than traditional adjuvants. Sugar-based compounds with beneficial adjuvant effects in neonatal vaccine models include delta inulin (Advax), curdlan, and trehalose 6,6'-dibehenate. Such compounds make interesting neonatal adjuvant candidates, either used alone or in combination with traditional innate immune adjuvants.

Post-Licensure Surveillance of Trivalent Live-Attenuated Influenza Vaccine in Children Aged 2-18 Years, Vaccine Adverse Event Reporting System, United States, July 2005-June 2012

BACKGROUND

The first trivalent live-attenuated influenza vaccine (LAIV3) was licensed in 2003 for use in healthy persons 5-49 years of age. In 2007, the US Food and Drug Administration expanded its indication to healthy children 2-4 years of age.

METHODS

We searched the Vaccine Adverse Event Reporting System (VAERS) for US reports after LAIV3 from July 1, 2005 to June 30, 2012 in children aged 2-18 years. Medical records were requested for nonmanufacturer reports coded as serious (ie, death, hospitalization, prolonged hospitalization, life-threatening illness, disability). We characterized electronic data and clinically reviewed all serious reports and reports of special interest. Empirical Bayesian data mining was used to identify new or unexpected adverse events (AEs).

RESULTS

During the study period, VAERS received 2619 US LAIV3 reports for children aged 2-18 years; 197 (7.5%) reports were serious, including 5 deaths. The 2 most frequent nonfatal serious reports involved neurological and respiratory systems, with 56 (29.2%) and 43 (22.4%) reports, respectively. The most frequent neurological diagnoses were seizures and Guillain-Barré Syndrome, and the most frequent respiratory conditions were pneumonia and asthma or reactive airway disease. Data mining showed increased proportions for reports of medication errors, most commonly vaccine administration errors not associated with an AE.

CONCLUSIONS

In this VAERS analysis of reports following LAIV3, we found no new or unexpected AEs patterns. Reports of LAIV3 administration to persons, for whom it is not recommended, including children with a history of asthma or reactive airway disease or wheezing, indicate that ongoing monitoring and education in vaccine indications are needed.

Vaccination of children with a live-attenuated, intranasal influenza vaccine - analysis and evaluation through a Health Technology Assessment

BACKGROUND

Influenza is a worldwide prevalent infectious disease of the respiratory tract annually causing high morbidity and mortality in Germany. Influenza is preventable by vaccination and this vaccination is so far recommended by the The German Standing Committee on Vaccination (STIKO) as a standard vaccination for people from the age of 60 onwards. Up to date a parenterally administered trivalent inactivated vaccine (TIV) has been in use almost exclusively. Since 2011 however a live-attenuated vaccine (LAIV) has been approved additionally. Consecutively, since 2013 the STIKO recommends LAIV (besides TIV) for children from 2 to 17 years of age, within the scope of vaccination by specified indications. LAIV should be preferred administered in children from 2 to 6 of age. The objective of this Health Technology Assessment (HTA) is to address various research issues regarding the vaccination of children with LAIV. The analysis was performed from a medical, epidemiological and health economic perspective, as well as from an ethical, social and legal point of view.

METHOD

An extensive systematic database research was performed to obtain relevant information. In addition a supplementary research by hand was done. Identified literature was screened in two passes by two independent reviewers using predefined inclusion and exclusion criteria. Included literature was evaluated in full-text using acknowledged standards. Studies were graded with the highest level of evidence (1++), if they met the criteria of European Medicines Agency (EMA)-Guidance: Points to consider on applications with 1. meta-analyses; 2. one pivotal study.

RESULTS

For the medical section, the age of the study participants ranges from 6 months to 17 years. Regarding study efficacy, in children aged 6 months to ≤7 years, LAIV is superior to placebo as well as to a vac-cination with TIV (Relative Risk Reduction - RRR - of laboratory confirmed influenza infection approx. 80% and 50%, respectively). In children aged >7 to 17 years (= 18th year of their lives), LAIV is superior to a vaccination with TIV (RRR 32%). For this age group, no studies that compared LAIV with placebo were identified. It can be concluded that there is high evidence for superior efficacy of LAIV (compared to placebo or TIV) among children aged 6 months to ≤7 years. For children from >7 to 17 years, there is moderate evidence for superiority of LAIV for children with asthma, while direct evidence for children from the general population is lacking for this age group. Due to the efficacy of LAIV in children aged 6 months to ≤7 years (high evidence) and the efficacy of LAIV in children with asthma aged >7 to 17 years (moderate evidence), LAIV is also very likely to be efficacious among children in the general population aged >7 to 17 years (indirect evidence). In the included studies with children aged 2 to 17 years, LAIV was safe and well-tolerated; while in younger children LAIV may increase the risk of obstruction of the airways (e.g. wheezing). In the majority of the evaluated epidemiological studies, LAIV proved to be effective in the prevention of influenza among children aged 2-17 years under everyday conditions (effectiveness). The trend appears to indicate that LAIV is more effective than TIV, although this can only be based on limited evidence for methodological reasons (observational studies). In addition to a direct protective effect for vaccinated children themselves, indirect protective ("herd protection") effects were reported among non-vaccinated elderly population groups, even at relatively low vaccination coverage of children. With regard to safety, LAIV generally can be considered equivalent to TIV. This also applies to the use among children with mild chronically obstructive conditions, from whom LAIV therefore does not have to be withheld. In all included epidemiological studies, there was some risk of bias identified, e.g. due to residual confounding or other methodology-related sources of error. In the evaluated studies, both the vaccination of children with previous illnesses and the routine vaccination of (healthy) children frequently involve cost savings. This is especially the case if one includes indirect costs from a societal perspective. From a payer perspective, a routine vaccination of children is often regarded as a highly cost-effective intervention. However, not all of the studies arrive at consistent results. In isolated cases, relatively high levels of cost-effectiveness are reported that make it difficult to perform a conclusive assessment from an economic perspective. Based on the included studies, it is not possible to make a clear statement about the budget impact of using LAIV. None of the evaluated studies provides results for the context of the German healthcare setting. The efficacy of the vaccine, physicians' recommendations, and a potential reduction in influenza symptoms appear to play a role in the vaccination decision taken by parents/custodians on behalf of their children. Major barriers to the utilization of influenza vaccination services are a low level of perception and an underestimation of the disease risk, reservations concerning the safety and efficacy of the vaccine, and potential side effects of the vaccine. For some of the parents surveyed, the question as to whether the vaccine is administered as an injection or nasal spray might also be important.

CONCLUSION

In children aged 2 to 17 years, the use of LAIV can lead to a reduction of the number of influenza cases and the associated burden of disease. In addition, indirect preventive effects may be expected, especially among elderly age groups. Currently there are no data available for the German healthcare setting. Long-term direct and indirect effectiveness and safety should be supported by surveillance programs with a broader use of LAIV. Since there is no general model available for the German healthcare setting, statements concerning the cost-effectiveness can be made only with precaution. Beside this there is a need to conduct health eco-nomic studies to show the impact of influenza vaccination for children in Germany. Such studies should be based on a dynamic transmission model. Only these models are able to include the indirect protective effects of vaccination correctly. With regard to ethical, social and legal aspects, physicians should discuss with parents the motivations for vaccinating their children and upcoming barriers in order to achieve broader vaccination coverage. The present HTA provides an extensive basis for further scientific approaches and pending decisions relating to health policy.

Assessing the evidence: live attenuated influenza vaccine in children younger than 2 years. A systematic review

BACKGROUND

Live attenuated influenza vaccine (LAIV) is effective in children but contraindicated in children <2 years of age.

METHODS

We searched Medline, EMBASE, the Cochrane Library, Web of Science, Scopus, PsycInfo and CINAHL through February 2013 for existing systematic reviews, randomized controlled trials (RCTs) and observational studies (for safety). We included studies enrolling healthy children <2 years of age who received LAIV, compared with placebo or inactivated influenza vaccine (IIV). Data were extracted independently by 2 investigators. The relative risk (RR) was pooled across studies using the random effects model.

RESULTS

We found 7 eligible randomized controlled trials and 2 observational studies. Randomized controlled trials included 6281 children and were at low to moderate risk of bias. LAIV reduced the incidence of influenza compared with placebo (relative risk = 0.36, 95% confidence interval: 0.23-0.58, P < 0.05) with a number needed to vaccinate of 17. LAIV increased the incidence of minor side effects (fever and rhinorrhea). LAIV had a similar effect in preventing influenza (relative risk = 0.76, 95% confidence interval: 0.45-1.30, P > 0.05) compared with inactivated influenza vaccine. There was an increase of hospitalization rate (post hoc analysis) and medical attended wheezing with LAIV.

CONCLUSIONS

LAIV is highly effective in children <2 years of age compared with placebo and is as effective to inactivated influenza vaccine. The safety profile of LAIV is reasonable although evidence is sparse. LAIV may be considered as an option in this age group particularly during seasons with vaccine shortage.

The rational use of influenza vaccines in healthy children and children with underlying conditions

PURPOSE OF REVIEW

This review discusses why influenza should be considered an important clinical problem even in healthy children, and what can be expected from the use of influenza vaccines in pediatrics.

RECENT FINDINGS

It has been demonstrated that not only children with an underlying disease but also otherwise healthy children can suffer from severe influenza. The greatest clinical problems arise during the first 23 months of life, but a substantial number of children aged 2-5 years and more than 5 years can die or be hospitalized. This suggests that adequate prophylactic measures should be planned for all children, regardless of their age. An influenza vaccination can be administered using a trivalent inactivated influenza virus or live attenuated influenza virus vaccine, and in both cases seems to be highly cost-effective. However, the actual use of influenza vaccines in children continues to be less than officially recommended.

SUMMARY

Influenza is a clinical problem for children at risk because of underlying disease and previously healthy children. Effective vaccines are currently available, and their extensive pediatric use seems to be associated with significant clinical and socioeconomic advantages.

Update on universal annual influenza immunization recommendations for children

PURPOSE OF REVIEW

To provide an update of current recommendations and research findings on universal annual influenza immunization of children.

RECENT FINDINGS

The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention and the American Academy of Pediatrics now recommend annual influenza vaccination for all children 6 months through 18 years. New research has examined the effect of 'herd immunity' associated with immunizing all school-aged children, the suboptimal antigenic match between the trivalent vaccine strains and circulating virus strains of last 2007-2008 influenza season, the efficacy of live attenuated influenza vaccine versus trivalent inactivated influenza vaccine, and the tolerance for influenza vaccine in infants less than 6 months of age. With a goal of improving the overall rates of influenza immunization and an eye toward the anticipated increase in volume with expansion of the universal recommendations in children, Advisory Committee on Immunization Practices and American Academy of Pediatrics emphasize the value of extending the timeframe for immunization beyond December and into April, establishing school-based immunization programs and other alternative vaccination sites outside medical homes, and conducting large, population-based studies that examine the overall impact of universal childhood influenza immunization.

SUMMARY

Annual influenza vaccination recommendations have been expanded, and research continues on vaccine efficacy, administration, and cost associated with vaccinating all school-aged children.