Majority of mumps cases are among the vaccinated, CDC finds

Mumps cases continue to circulate in the U.S., largely among vaccinated people, including children.

According to the report from the Centers for Disease Control and Prevention, one-third of mumps cases in the U.S. from 2007 to 2019 were reported in children and adolescents.

"Before that, large outbreaks of mumps among people who were fully vaccinated were not common, including among vaccinated children," said Mariel Marlow, an epidemiologist at the CDC who led the new study.

Experts aren't sure why vaccinated people get mumps, but multiple factors appear to be affecting immunity in vaccinated people, including a lack of prior exposure to the virus, waning immunity and the circulation of genotypes the vaccine doesn't contain.

Mumps cases decreased last year compared to the previous six years, but the illness continued to circulate in the U.S. despite distancing, lockdowns and masking.

Because mumps has continued to circulate globally during the pandemic, she expects cases and outbreaks of mumps nationally that could be worsened by a bigger unvaccinated population to continue.

Adjusting the schedule is nothing new: The CDC's Advisory Committee on Immunization Practices initially recommended a single dose of the mumps vaccine for routine use in 1977 and upped it to two doses in 1989.In 2017, the panel suggested that a third dose of the MMR vaccine may be given to people at high risk of catching mumps during large outbreaks.

https://www.nbcnews.com/health/health-news/majority-mumps-cases-are-vaccinated-cdc-finds-rcna6482