| Study characteristics |
| Methods |
Cohort study ‐ USA |
| Participants |
Children aged 12 to 60 months who received a first dose of MMRV in February 2006 to June 2007. Participants were optimally matched on age, sex, and calendar date of vaccination to children who had received MMR+V concomitantly in November 2003 to January 2006, before MMRV licensure. Potential cases of febrile convulsion were identified through administrative data and adjudicated by expert panel, according to prespecified criteria. |
| Interventions |
MMRV: ProQuad, a combined formulation of measles, mumps, rubella, and varicella (MMRV) vaccine that contains components of 2 Merck vaccines, MMR‐II (MMR) and Varivax (V), was approved in the USA in September 2005. Before MMRV was available, MMR and V were usually given concomitantly as 2 separate injections. |
| Outcomes |
Study participants were followed through health encounter and claims records to identify all potential occurrences of convulsion. Potential convulsions were identified as occurring on any visit with a diagnosis coded as 779.0 (neonatal seizures), 333.2 (myoclonus), 345 (epilepsy), 780.39 (other convulsion), 780.3 (convulsion), 780.31 (simple febrile convulsion), or 780.32 (complex febrile convulsion) regardless of setting (e.g. inpatient, outpatient, emergency department, or outside facility). |
| Funding Source |
Pharmaceutical industry |
| Notes |
Conclusion: these data suggest that the risk of febrile convulsion is increased in days 5 to 12 following vaccination with MMRV as compared to MMR+V given separately during the same visit, when postvaccination fever and rash are also increased in clinical trials. Whilst there was no evidence of an increase in the overall month following vaccination, the elevated risk during this time period should be communicated and needs to be balanced with the potential benefit of a combined vaccine. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| PCS/RCS ‐ exposed cohort selection |
Low risk |
Adequate ‐ registry KPSC ‐ representative of the exposed |
| PCS/RCS ‐ non‐exposed cohort selection |
Low risk |
Adequate ‐ drawn from the same community |
| PCS/RCS ‐ comparability |
Low risk |
Adequate ‐ exposed and non‐exposed were matched for age, sex, vaccination calendar day and month |
| PCS/RCS ‐ assessment of outcome |
Low risk |
Adequate ‐ hospital record |
| Summary Risk of Bias assessment |
Low risk |
Plausible bias is unlikely to have seriously altered the results. |
