No increased risk of febrile seizure after MMRV vaccine
Children under 2 years who received the measles-mumps-rubella-varicella (MMRV) vaccine as a second measles-containing vaccine (MCV) following an MMR vaccine did not have an elevated risk of febrile seizures (FS), according to an Australian study. The introduction of the MMRV vaccine also increased MCV coverage in Australia.
Children aged 11–23 months who received the MMRV vaccine as their second MCV did not experience an increased risk of FS within 5–12 days of MMRV vaccine administration (relative incidence [RI], 1.08, 95 percent confidence interval [CI], 0.55–2.13; p=0.82). [JAMA Pediatr 2017;doi:10.1001/jamapediatrics.2017.1965]
In contrast, the risk of FS was elevated in the 5–12 days following MMR vaccine administration (first MCV; IR, 2.71, 95 percent CI, 1.71–4.29; p<0.001).
In this multicentre (five tertiary paediatric hospitals in Australia), prospective safety surveillance study conducted between May 2013 and June 2014 by the Paediatric Active Enhanced Disease Surveillance network, 1,668 unique cases of FS (median age at first FS, 21 months) occurred among 1,471 children aged 11–59 months.
Of the 391 patients aged 11–23 months who had ≥1 FS (465 total number of unique FS episodes), 71.1 percent had received the MMR vaccine followed by the MMRV vaccine, 24.8 percent had received the MMR vaccine only, and 4.1 percent had received neither.
Two-dose MCV coverage increased to 93.8 percent at age 36 months within 2.5 years of the MMRV vaccine introduction, while there was a 13.5 percent improvement in on-time immunization with the second MCV vaccine (within 30 days of recommended age) and a 4 percent improvement in one-dose varicella vaccine coverage.
“Our evaluation demonstrates that MMRV vaccine introduction in Australia has been associated with improved coverage and timeliness of protection against all four diseases … with no effect on the overall safety profile of the programme,” said the researchers led by Associate Professor Kristine Macartney from The Children’s Hospital at Westmead, New South Wales, Australia.
Reports of an increased risk of febrile seizures following MMRV vaccine administration compared with separate MMR and varicella vaccines led to the US Advisory Committee on Immunization Practices recommending, in 2009, that the MMR and varicella vaccine be administered as separate injections over the MMRV vaccine for the first dose of these vaccines at age 12–47 months, said Dr Cindy Weinbaum from the Centers for Disease Control and Prevention and Dr Walter Orenstein from the Emory Vaccine Center, Atlanta, Georgia, US, in a commentary. [JAMA Pediatr 2017;doi:10.1001/jamapediatrics.2017.2375; https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5903a1.htm]
The MMRV vaccine was recommended as the second dose as there was no evidence of an elevated risk of FS compared with separate vaccines when administered as the second dose, they said.
The researchers acknowledged that the findings may not be representative of all Australian children with FS and did not discount the potential role of confounding factors. The results were also mostly based on administration of one of the two available MMRV vaccines.