The potency of the varicella-zoster virus in the measles-mumps-rubella-varicella (MMRV) vaccine is at least 7 times higher than the potency in the monovalent varicella vaccine, and this may contribute to the increased fever after the MMRV vaccine.
After vaccination at 12 through 23 months of age, there are more febrile seizures among children who receive the MMRV vaccine (7-9 per 10,000 children) than among children who receive the MMR and varicella vaccines separately (3-4 per 10,000 children).
As a result, one would expect an additional febrile seizure for approximately 2300 to 2600 children 12 through 23 months old vaccinated with the MMRV compared with separate MMR and varicella vaccines.
This increased risk of febrile seizures does not appear to occur among older children 4 through 6 years of age receiving the second dose of MMRV.
Based on these observations, the AAP’s Committee on Infectious Diseases updated their recommendations for use of MMRV and monovalent varicella vaccines in children. Their recommendations appear in the August 29th online issue of Pediatrics.
For the first dose at ages 12 through 47 months, the AAP recommends “that either MMR and varicella vaccines administered separately or MMRV can be used. Use of separate MMR and varicella vaccines averts the slight increase in risk of fever and febrile seizures after MMRV administration but at the cost of the pain associated with an extra injection and the risk of an infant falling behind schedule if all vaccines indicated at that visit are not given.”
The risks and benefits of both vaccination options should be discussed with parents or caregivers, and if communication barriers impede this full discussion, then providers should administer MMR and varicella vaccines separately.
When the first dose is administered at age 48 months or older, and for dose 2 at any age, the guidelines indicate that “use of the MMRV generally is preferred over separate injections of its equivalent component vaccines because of the decreased number of injections required with the MMRV.”
Finally, the guidelines recommend the use of MMR and varicella vaccines separately for children with a personal or family history of seizures, in whom the risks of using the MMRV generally outweigh the benefits.
Fact sheets for the vaccines may be found at www.cdc.gov/vaccines/vpd-vac/combovaccines/mmrv/vacopt-factsheet-hcp.htm, and the updated Vaccine Information Statement (VIS) is at www.cdc.gov/vaccines/pubs/vis/downloads/vis-mmrv.pdf. Current availability of the MMRV can be accessed at www.cdc.gov/vaccines/vac-gen/shortages/default.htm#4.
Policy Statement—Prevention of Varicella: Update of Recommendations for Use of Quadrivalent and Monovalent Varicella Vaccines in Children