Why mumps has made a comeback
Increasing cases of mumps over the past decade in Australia and around the world have stumped experts, unsure if the outbreaks are vaccine-related or caused by resistant viruses.
Now a team of Harvard researchers say they can confirm the live attenuated vaccine is not performing as well as expected.
In a paper in Science Translational Medicine, they attribute the problem to “vaccine waning”.
However, they say adding a third vaccine dose may be all that’s needed.
Synthesising data from six studies of mumps vaccine efficacy, the authors say on average, vaccine-derived immune protection wanes 27 years after vaccination.
This explains why the problem is mainly confined to 18-29-year-olds, and not in older people who gained immunity through natural infection.
The authors say there is no evidence that the emergence of heterologous virus genotypes has contributed to changes in vaccine effectiveness over time. A mathematical model of transmission has confirmed the central role of waning immunity.
“Outbreaks from 2006 to the present among young adults, and outbreaks in the late 1980s and early 1990s among adolescents, aligned with peaks in mumps susceptibility of these age groups predicted to be due to loss of vaccine-derived protection,” they write.
The authors suggest the best way to tackle the problem may be either routine use of a third vaccine dose at age 18 or booster dosing throughout adulthood.
This should be assessed in clinical trials, they add.
You can access the study here.