| Study characteristics |
| Methods |
A retrospective study design was used to reveal the risk factors associated with febrile convulsion in study participants ‐ Israel |
| Participants |
All participants were aged 10 to 24 months at vaccination, and received the immunisation in community public health well‐child clinics from 1 January 2005 to 31 December 2009. The study group consisted of 8344 MMRV vaccinees immunised from 1 September 2008 (at limitation of national vaccination policy change from MMR to MMRV) until 31 December 2009. The comparison group consisted of 90,294 MMR recipients immunised from 1 January 2005 until 31 August 2008. The observation period captured 40 days following MMR/MMRV administration. Individual data on FC were available for all study participants from birth until 40 days postimmunisation. These data were used to calculate the pre‐vaccination age‐related risk of FC. |
| Interventions |
MMRV and MMR vaccines. Immunisation data were received for the period of 2005 to 2009 from the computerised system of the Israeli Ministry of Health. MMRV cohort N = 32,148 participants; MMR+V cohorts N = 32,145 participants. MMRV Priorix‐Tetra. MMR (Priorix) produced by GSK. Priorix‐Tetra combines the components of 2 of GSK's live attenuated vaccines, MMR (Priorix) and varicella vaccine (Varilrix). |
| Outcomes |
Febrile convulsion: validation FC cases were retrieved using the following coded and free‐text diagnoses: “convulsions in newborn”, “convulsions”, “febrile convulsions”, “complex febrile convulsions”, “other convulsions”. Children diagnosed with FC differential diagnoses during the observational period, i.e. head trauma, epilepsy, or central nervous system infection, were excluded from the study. The exact coded and free‐text diagnoses used to depict coincidental differential conditions were: “concussion”, “cerebral disease”, “acquired hydrocephalus”,“cerebral palsy”, “cerebral cyst”, “epilepsy”, “meningism”, types of “bacterial meningitis”, “encephalitis”, “meningococcal meningitis”, and “aseptic viral meningitis”. Children were also excluded from the study if they had a history of mumps, measles, rubella, or varicella prior to vaccination. |
| Funding Source |
Pharmaceutical industry |
| Notes |
Conclusion: given the low number of MMRV‐specific FC cases, their transient nature, and the benefit of vaccination, the overall benefit‐risk of the vaccine can be considered favourable. Nonetheless, the option of separate immunisation with MMR+V should be offered to parents, in order to maintain sufficient vaccine uptake in the population. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| PCS/RCS ‐ exposed cohort selection |
Low risk |
Adequate ‐ Clalit Health Services' 53% Israel's population ‐ vaccination status from computerised system of Israeli Ministry of Health |
| PCS/RCS ‐ non‐exposed cohort selection |
Low risk |
Adequate ‐ drawn from the same population |
| PCS/RCS ‐ comparability |
Low risk |
Adequate ‐ homogeneous age |
| PCS/RCS ‐ assessment of outcome |
Low risk |
Adequate ‐ medical record |
| Summary Risk of Bias assessment |
Low risk |
Plausible bias is unlikely to have seriously altered the results. |
