MMRV Combo Vaccine Is About as Safe as Separate MMR and Varicella Shots
Key clinical point: If you’re okay with a slightly higher risk of febrile seizures, MMRV vaccine might be the way to go with your toddlers.
Major finding: There were 0.86 cases of meningitis/encephalitis per 100,000 doses of MMR+V and 1.86 cases per 100,000 doses of MMRV within 3 weeks of vaccination; similarly, there were 0.52 cases of arthritis/arthralgia per 100,000 doses for MMR+V and 0.84 cases for MMRV per 100,000 doses. The differences “could be ruled out with 95% confidence,” according to the investigators.
Data source: Diagnostic codes after 123,200 doses of the MMRV combination vaccine and 584,987 doses of MMR+V vaccines in children 12-23 months old.
Disclosures: Dr. Klein, Dr. Roger Baxter, and Allison Naleway, Ph.D., disclosed research funding from Merck, which manufactures the vaccines used in the study, and GlaxoSmithKline, among other industry ties. Dr. Edward A. Belongia reported research support from Medimmune. The remaining authors reported no relevant financial disclosures. The work was funded by the CDC.
FROM PEDIATRICS
With both vaccines, however, there were around 800 cases of fever per 100,000 doses within 7-10 days of the shots; there were also 52.37 febrile seizures per 100,000 doses of MMR+V, and 101.01 per 100,000 doses of MMRV (relative risk, 1.99 MMRV, compared with MMR+V).
The fever and seizure findings aren’t new; “measles-containing vaccines are” known to be associated with seizure, fever, and ITP, the investigators noted, and MMRV’s higher seizure risk has been reported before.
As expected, both immunization strategies increased the risk of ITP, which peaked 2-4 weeks after vaccination, but the absolute number of cases was small, about 5-10 per 100,000 doses. “To our knowledge, [this is] the first report that MMRV is associated with a similar increased risk of ITP during the same postvaccination risk intervals as MMR,” the investigators said.
MMRV and MMR+V both were associated with a small and surprising decrease in ataxia, but “this observation is more likely due to chance, outcome misclassification, or other unmeasured confounding,” they said.
Dr. Klein, Dr. Roger Baxter, and Allison Naleway, Ph.D., disclosed research funding from Merck, which manufactures the vaccines used in the study, and GlaxoSmithKline, among other industry ties. Dr. Edward A. Belongia reported research support from Medimmune. The remaining authors reported no relevant financial disclosures. The work was funded by the CDC.
