Adverse Events After MMR or MMRV Vaccine in Infants Under Nine Months Old

Emily Jane Woo, MD, MPH, Scott K. Winiecki, MD, Deepa Arya, MD, MPH, MBA, and Judy Beeler, MD


Pediatr Infect Dis J. 2016;35(8):e253-e257. 

In This Article

Abstract and Introduction


Background: In the United States, measles is resurging, with more than 700 confirmed cases since January 2014. During measles outbreaks, vaccination as early as at 6 months of age is sometimes recommended for infants who are at risk for exposure.

Methods: We searched the Vaccine Adverse Event Reporting System for reports of measles, mumps and rubella vaccine combined or measles, mumps, rubella and varicella vaccine combined vaccination in children less than 9 months of age. We performed a clinical assessment of each report and summarized the frequency, range, onset time and severity of adverse events.

Results: After excluding 346 reports because they were duplicates or because they contained insufficient information about the child's age or vaccine(s), we retained 204 reports in the analysis, including 35 (17%) that were serious. Among the 169 nonserious reports, more than half (88; 52%) described a vaccination error without any adverse event per se. Other nonserious reports described fever, injection reactions and gastrointestinal symptoms. Serious adverse events included developmental disorders, fever and fussiness. There were 44 reports of fever, but only 4 cases began 5–12 days after immunization, the peak risk window. The vast majority of fever reports listed concomitant vaccines, such as diphtheria and tetanus toxoids, acellular or whole-cell pertussis vaccine.

Conclusions: This review did not identify any major safety concerns. These findings may facilitate discussions about the risks and benefits of vaccinating infants who are potentially exposed to this life-threatening disease.


In the United States, measles has reached a high record because indigenous circulation was eliminated in 2000, with more than 700 confirmed cases since January 2014.[1–3] Pneumonia, hepatitis and other serious complications have resulted in hospitalization.[1] In outbreaks in the United States since 2008, confirmed cases of measles have affected more than 100 infants.[3] Thus, measles remains a critical public health concern.[4]

The Advisory Committee on Immunization Practices in the United States currently recommends that the first dose of measles, mumps and rubella (MMR) virus vaccine combined be given to children on or after their first birthday.[5] During outbreaks or before travel to a measles-endemic area,[6] vaccination as early as at 6 months of age (followed by routine vaccination at 12–15 months and 4–6 years of age) may be recommended.[5,6] Measles vaccine was initially licensed for routine use at 9 months of age.[7] Because monovalent measles vaccine is no longer distributed in the United States,[5] MMR vaccine is used for active immunization against measles. Although effectiveness and immunogenicity of monovalent measles vaccine at 6 months of age have been evaluated,[8–11] few trials evaluating the safety of MMR in very young infants have been performed. In a randomized trial among infants 8 and 12 months old, He et al[12] evaluated the safety of an MMR vaccine manufactured by the Shanghai Institute of Biological Products Company (Shanghai, China). However, similar trials using the US-licensed MMR vaccine have not been conducted.

Because of the resurgence of measles in the United States,[1–3] immunization of young infants may be necessary under certain circumstances. Understanding the adverse event profile of MMR in this age group is therefore a matter of public health exigency. To address this important question, we searched the Vaccine Adverse Event Reporting System (VAERS) and reviewed reports following MMR or measles, mumps, rubella and varicella (MMRV) virus vaccine combined immunization in infants younger than 9 months of age.