An exhaustive study of vaccines containing the measles virus found that the risk of seven adverse events many parents fear are unlikely to occur as a result of vaccination. The remaining two fears occur at such a low rate that it is safer for a child to be vaccinated than to get the measles.
Dr. Nicola P. Klein is lead author of the study which was recently published in the medical journal, Pediatrics. Klein, co-director of the Kaiser Permanente Vaccine Study Center, and her colleagues analyzed 12 years of data, from January 2000 through June 2012, to document the adverse events that occurred after children aged 12 to 23 months had been vaccinated with one of two popular measles-containing vaccines:
- MMRV — one-dose combined vaccine for measles, mumps, rubella, and varicella
- MMR + V — one dose of combined vaccine for measles, mumps, and rubella plus a second vaccine for varicella administered as a separate dose on the same day
Klein’s research team evaluated the effects of 123,200 MMRV vaccinations and 584,887 MMR + V vaccinations.
The researchers were looking for blood, immune system, or neurological vaccine-related incidents of:
- Acute disseminated encephalomyelitis
- Immune thrombocytopenia purpura
- Kawasaki disease
- Meningitis / Encephalitis
The researchers also evaluated the vaccination records for evidence of fever or febrile seizures following vaccinations containing the measles virus.
"There were few or zero events for several outcomes following vaccination. These findings indicate that even if an increased risk for these outcomes exists, the risk is low and rare. This should reassure parents that these outcomes are unlikely after either vaccine," according to the research team.
The Klein study did confirm findings of previous studies that found a slightly increased risk of fever and febrile seizures occurring seven to ten days after 1-year-old children were vaccinated. The risk of such events is fewer than one febrile seizure per every 1,000 vaccinations (less than 0.001%). Previous studies involving older children, ages 4 to 6 years, have found no link between these vaccines and fever or febrile seizure.
To minimize risk of fever and/or febrile seizures to year-old babies, Klein recommends the MMR + V vaccine rather than the combined MMRV vaccine.
According to the US Centers for Disease Control and Prevention, 30% of all people who get the measles will suffer complications that include diarrhea, ear infections, and pneumonia. Young children and adults are at greatest risk for complications of measles.
Klein said, "This level of safety monitoring for vaccines can give the public confidence that vaccine surveillance is ongoing and that if a safety problem existed, it would be detected.” The research team also notes that if any adverse reactions other than the nine the team targeted had been identified, their existence would’ve been included in their report of the study but no additional adverse reactions were found.