Hypotonic-Hyporesponsive Episode (HHE) as an adverse event following immunization: case definition and guidelines for data collection, analysis, and presentation

Hypotonic-hyporesponsive Episodes After Diphtheria, Tetanus and Acellular Pertussis Vaccination

BACKGROUND

Hypotonic-hyporesponsive episode (HHE) after whole cell pertussis vaccination is a known adverse event. Less is known about the risk of HHE after administration of acellular pertussis vaccines.

METHODS

Using parental interviews, this study actively surveyed for HHE among infants after doses 1 and 2 of acellular pertussis vaccine.

RESULTS

We interviewed the parents of 52,531 infants. HHE was reported at a rate of 22.8 per 100,000 doses (95% CI: 11.8-39.9) of acellular pertussis vaccine, approximately 45 episodes per 100,000 children.

CONCLUSIONS

These rates are lower than HHE rates reported after whole cell pertussis vaccines and within the range of HHE rates reported in other studies of acellular pertussis vaccines.

NSW annual report describing adverse events following immunisation, 2010

AIM

This report summarises Australian passive surveillance data for adverse events following immunisation in NSW for 2010.

METHODS

Analysis of de-identified information on all adverse events following immunisation reported to the Therapeutic Goods Administration.

RESULTS

424 adverse events following immunisation were reported for vaccines administered in 2010; this is 6% lower than 2009 but 24% higher than 2008 and the second highest number since 2003. A total of 274 (65%) adverse events involved seasonal or pandemic influenza vaccines. Reports were predominantly of mild transient events: the most commonly reported reactions were fever, allergic reaction, injection site reaction, malaise and headache. Only 9% of the reported adverse events were serious in nature, including eight reports of febrile convulsions in children following seasonal influenza vaccine.

CONCLUSION

The large number of reports in 2010 is attributable to the high rates of fever and febrile convulsions in children after vaccination with 2010 seasonal trivalent influenza vaccine, as well as pandemic (H1N1) 2009 influenza vaccine.

Surveillance of adverse effects following vaccination and safety of immunization programs

The aim of the review was to analyze conceptual and operational aspects of systems for surveillance of adverse events following immunization. Articles available in electronic format were included, published between 1985 and 2009, selected from the PubMed/Medline databases using the key words "adverse events following vaccine surveillance", "post-marketing surveillance", "safety vaccine" and "Phase IV clinical trials". Articles focusing on specific adverse events were excluded. The major aspects underlying the Public Health importance of adverse events following vaccination, the instruments aimed at ensuring vaccine safety, and the purpose, attributes, types, data interpretation issues, limitations, and further challenges in adverse events following immunization were describe, as well as strategies to improve sensitivity. The review was concluded by discussing the challenges to be faced in coming years with respect to ensuring the safety and reliability of vaccination programs.

Immunogenicity and safety of an investigational combined haemophilus influenzae type B-Neisseria meningitidis serogroups C and Y-tetanus toxoid conjugate vaccine

BACKGROUND

Neisseria meningitidis serogroups B, C, and Y cause most meningococcal disease in industrialized countries. A Haemophilus influenzae type b-meningococcal serogroups C and Y-tetanus toxoid conjugate vaccine (HibMenCY-TT) was evaluated.

METHODS

A total of 1104 infants (randomized 3:1:1) were vaccinated at 2, 4, and 6 months with HibMenCY-TT, MenC-CRM197 + Hib-TT, or Hib-TT. At 12 to 15 months, HibMenCY-TT and MenC-CRM-primed children received HibMenCY-TT; Hib-TT-primed received N. meningitidis serogroup B Hib-outer membrane protein complex. Antibody concentrations and rabbit/human complement serum bactericidal antibody titers (rSBA/hSBA) were determined. Safety was monitored after each dose (diary cards for first 31 days) until 6 months postdose 4.

RESULTS

Postdose 3, rates of antipolyribosylribitol phosphate ≥ 1 μg/mL and rSBA-MenC ≥1:128 in HibMenCY-TT recipients were noninferior to licensed controls. Percentages reaching 0.15 μg/mL (1.0 μg/mL postdose 3) and antipolyribosylribitol phosphate GMC were significantly higher after HibMenCY-TT than Hib-TT postdose 2 and postdose 3. The GMC remained significantly higher before and after dose 4. Proportions of HibMenCY-TT recipients with rSBA ≥ 1:8 were 95.6% (MenC), 98.6% (MenY) postdose-2, ≥ 99% for MenC/Y postdose 3 and 4; hSBA ≥ 1:4 were 95.5% (MenC), 89.8% (MenY) postdose 2, >97% for MenC/Y postdose 3 and 4. HibMenCY-TT had a similar safety profile to control vaccines.

CONCLUSIONS

HibMenCY-TT induced noninferior Hib and MenC responses compared with monovalent Hib and MenC conjugates with a comparable safety profile. Bactericidal antibodies against MenC/Y were induced after 2 doses of HibMenCY-TT.

NSW Annual Adverse Events Following Immunisation Report, 2009

AIM

This is the first annual report for NSW of adverse events following immunisation. It summarises Australian passive surveillance data for adverse events following immunisation for NSW for 2009.

METHODS

Analysis of de-identified information on all adverse events following immunisation reported to the Therapeutic Goods Administration.

RESULTS

450 adverse events following immunisation were reported for vaccines administered in 2009; this is 32% higher than 2008 and the highest since 2003. The increase was almost entirely attributed to the commencement of the pandemic (H1N1) 2009 influenza vaccine in September 2009. Only 6% of the reported adverse events were serious in nature and the most commonly reported reactions were allergic reaction, injection site reaction, fever and headache.

CONCLUSION

Reports of adverse events following immunisation in 2009 were dominated by the pandemic (H1N1) 2009 influenza vaccine. A large proportion of these adverse events were reported directly to the Therapeutic Goods Administration by members of the public. Reports were predominantly mild transient events, similar to those expected from the seasonal flu vaccine.

Reactogenicity of infant whole cell pertussis combination vaccine compared with acellular pertussis vaccines with or without simultaneous pneumococcal vaccine in the Netherlands

BACKGROUND

In addition to the routine enhanced passive safety surveillance of the Dutch National Vaccination Programme, RIVM (National Institute for Public Health and the Environment) started a large questionnaire study enrolling approximately 53,000 children from December 2003 until September 2007.

AIM

We intended to establish accurate frequency estimates for several more severe adverse events and to compare the incidence rates of three different infant vaccines that were used consecutively.

METHODS

Whole cell pertussis (wP) DTP-IPV-Hib vaccine (NVI) was replaced by acellulair pertussis (aP) in 2005, first Infanrix-IPV-Hib (GSK) followed by Pediacel (Sanofi) in 2006. Pneumococcal vaccine, Prevenar (Wyeth), was added for children born from April 2006.

RESULTS

Parents returned 28,796 questionnaires (response 54%), 15,069 for whole cell pertussis and 13,727 for acellular pertussis vaccine, including 4485 with pneumococcal vaccine. The OR for reported events was 3-6 for whole cell pertussis vaccine compared with acellular vaccine. This was true for prolonged crying for 3h and more after the first dose (1.5% versus 0.4%; 95 CI 1.1-1.9 and 95% CI 0.2-0.7, respectively), and very high fever of 40.5 degrees C and over following the fourth dose (0.8% versus 0.2%; 95% CI 0.5-1.1 and 0.06-0.3, respectively), while possible febrile convulsions were diagnosed only twice after the fourth dose in the whole cell vaccine group and one after acellular pertussis vaccine. Pallor was significantly more frequent after the first dose of whole cell pertussis than after acellulair pertussis vaccination (18.3% versus 3.4%; 95% CI 17.2-19.5 and 95% CI 2.8-4.0 respectively) Collapse after the first dose was rare in both vaccine groups (5 after whole cell vaccine and 1 after acellular vaccine). The addition of conjugated pneumococcal vaccine did not result in statistically significant increased rates of adverse events in the acellular vaccine group.

CONCLUSION

Whole cell pertussis vaccine showed a significantly higher reactogenicity regarding the adverse events analysed, while addition of conjugated pneumococcal vaccine administered simultaneously with acellular pertussis showed no statistically different adverse event profile.

The effect of age and dose number on the risk of collapse (hypotonic-hyporesponsive episode) after pertussis vaccination

The Netherlands vaccination schedule has been advanced by 1 month. The reporting rate of collapse or hypotonic-hyporesponsive episode increased from 5.2 [95% confidence interval (CI): 4.8-5.7] to 8.5 (95% CI: 8.0-9.1) and from 1.2 (95% CI: 1.0-1.4) to 2.5 (95% CI: 2.2-2.8) per 10,000 first and second doses, respectively. At 3 months of age it fell from 5.2 to 2.5. This suggests some protection by the first dose. Different mediators in primary and secondary immune response may play a role.

Hypotonic and hyporesponsive episodes after diptheria-tetanus-acellular pertussis vaccination

Administration of the discontinued diphtheria-pertussis-tetanus vaccine was occasionally associated with a hypotonic-hyporesponsive episode in infants. The whole bacterial cell pertussis component was the likely culprit. For this reason, an acellular pertussis component was developed and incorporated into a new vaccine commonly called diptheria-tetanus-acellular pertussis (DTaP). Administration of DTaP vaccine has been followed by remarkably few hypotonic or hyporesponsive episodes. This report describes one of these unusual events.

Vaccination, seizures and ‘vaccine damage’

PURPOSE OF REVIEW

Concerns about the safety of vaccination have plagued the community, with reduction in vaccine uptake resulting in increased risk of epidemics. Vaccination has been implicated in the cause of febrile seizures, 'vaccine encephalopathy' and autistic spectrum disorders. Evaluation of alleged associations is complicated by evolution in the vaccination field. This review focuses on the risk of seizures following vaccination and the alleged associations of vaccination with vaccine encephalopathy and also with autism spectrum disorders.

RECENT FINDINGS

Over the last decade the introduction of new vaccines such as the acellular pertussis vaccine has produced a reduction in seizures following vaccination, the outcome of which was benign even with older vaccines. New evidence emerged in 2006 showing that cases of alleged 'vaccine encephalopathy' are due to mutations within a sodium channel gene. The weight of epidemiological evidence does not support a relationship between vaccination and childhood epileptic encephalopathies or autism spectrum disorders.

SUMMARY

Vaccines are safer than ever before, but the challenge remains to convey this message to society in such a way that produces change in attitudes to vaccination and subsequent increase in vaccine coverage.

Performance of the Brighton collaboration case definition for hypotonic–hyporesponsive episode (HHE) on reported collapse reactions following infant vaccinations in the Netherlands

We reviewed collapse (sudden onset of pallor, limpness and hyporesponsiveness) following the first infant (DPTP+Hib) vaccination reported to the enhanced passive surveillance system of the Netherlands in 1994-2003. All 1303 reports identified by the current RIVM (National Institute for Public Health and Environment) case definition were captured by the Brighton Collaboration (BC) case definition, with in 17 (1.3%) reports insufficient information. Over the years the proportion of the highest level of diagnostic certainty (level 1) increased due to more complete data from 70% to over 90%. We checked the BC case definition also on a sample of cases (with pallor or hyporesponsiveness) not meeting RIVM's case definition for collapse at the time. Sixty out of 200 cases were captured by BC but again rejected by RIVM. The sensitivity BC levels 2 and 3 appeared too high. We recommend a more restrict case definition by the Brighton Collaboration with certain exclusion criteria to make it more specific. Furthermore a change in the specifications for levels 2 and 3 will increase specificity and accommodate for the loss of sensitivity.

Vaccination-related adverse events

Vaccine-related adverse events are uncommon and typically mild. Children may experience conditions such as rashes, fevers, syncope, protracted crying, or seizures shortly after receiving their routine immunizations. When children are brought to the emergency department or clinic to be evaluated for one of these conditions, the health care provider may be called upon to determine the likelihood that it was caused by a recently administered set of vaccines. This determination has substantial implications for medical care, including the safety of administering future vaccines. This article reviews the current understanding of vaccine-related adverse events. Using this information, clinicians should be able to identify those events likely to be related to vaccine administration and those that are not. The appropriate management of vaccine-related adverse events is also discussed.

Hypotonic-hyporesponsive episode in a 7-month-old infant after receipt of multiple vaccinations

A 7-month-old boy became difficult to arouse, was limp and had blue extremities 8 hours after immunization with intravenous poliovirus, diphtheria-tetanus toxoids-acellular pertussis, Haemophilus influenzae type b-hepatitis B virus and pneumococcal vaccines. The hypotonic-hyporesponsive episode had resolved by the time the infant was seen in an emergency department 1 hour later. The report describes hypotonic-hyporesponsive episode, encourages reporting of vaccine-associated adverse events and discusses prognosis and implications for subsequent immunization.