MMRV Vaccine Safe, With Rare Adverse Effects

A comparison of the measles-mumps-rubella-varicella (MMRV) vaccine with the separate measles-mumps-rubella (MMR) + varicella (MMR + V) vaccines revealed no new safety concerns. The new study, published online January 5 in Pediatrics, provides reassurance that adverse outcomes are unlikely with either vaccine.

Nicola P. Klein, MD, PhD, from the Kaiser Permanente Vaccine Study Center in Oakland, California, and colleagues reviewed the Vaccine Safety Datalink for children aged 12 to 23 months who received the vaccines from 2000 to 2012. Their database included 123,200 doses of MMRV and 584,987 doses of MMR + V.

The investigators studied seven main outcomes: anaphylaxis, immune thrombocytopenia purpura (ITP), ataxia, arthritis, meningitis/encephalitis, acute disseminated encephalomyelitis, and Kawasaki disease. They also evaluated incidence of seizure and fever.

MMR vaccine has previously been associated with seizure, fever, and ITP. The MMRV vaccine was licensed in 2006, and this new study represents a report of data from safety monitoring. All seven main outcomes (with the exception of arthritis) were evaluated during a focal risk interval that was identified as the window of time in which the event would be most likely to occur if the event were related to vaccination.

MMRV was associated with a slightly increased risk for fever relative to MMR + V at 7 to 10 days postvaccination.

Surprisingly, MMRV and MMR + V were both associated with a decreased incidence of ataxia diagnoses after vaccination.

The investigators found no difference in risk for ITP or any other adverse outcomes between recipients of the two vaccines. For example, the odds ratio for ITP was 11.3 (95% confidence interval, 1.9 - 68.2) for patients receiving MMRV compared with 10 (95% confidence interval, 4.5 - 22.5) for recipients of MMR + V.

The authors explain that if MMRV were associated with an increased risk for the seven main outcomes, the increase in risk would be low and rare, as it was undetectable in the large study.

They also note that they found no increased risk for anaphylaxis with either vaccine. This finding stands in contrast to a 2011 Institute of Medicine report that found support for a causal relationship between the MMR vaccine and anaphylaxis.

This study was supported by a subcontract with America’s Health Insurance Plans. Dr Klein and one coauthor report receiving research support from Merck & Co, GlaxoSmithKline, Sanofi-Pasteur, Pfizer, Novartis, MedImmune, and Nuron Biotech; another coauthor reports receiving research support from GlaxoSmithKline; and another coauthor reports receiving research support from MedImmune. The other authors have disclosed no relevant financial relationships.

Pediatrics. Published online January 5, 2015. Abstract

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