Reviewed by, Jen Cihlar, DO, Vanderbilt University Medical Center
Bottom line: In measles post-elimination settings, the risk for onward transmission from persons with measles secondary vaccination failure (SVF) is very low but not zero and in large outbreak situations, public health management of measles cases in unvaccinated persons could be prioritized before SVF cases. Additionally, using routine serologic testing for SVF, in addition to the standard PCR tests, may be a useful adjunct for risk stratification during outbreak management.
This systematic review sought to assess transmission risk for measles after secondary vaccination failure (SVF), in “post-elimination” high vaccination rate setting. Across the 14 studies, with >3030 exposed persons, there were 109 cases of lab confirmed measles SVF were identified, which from they determined an effective reproduction number of 0.063 (95% CI 0.0–0.5). The calculated secondary attack rate ranging from 0% to 6.25% (using data from 3/14 studies). Limitations included lack of standardized definition of SVF across studies (though most used was high IgG avidity level >60%), potential underreporting of outbreaks that yielded SVF, small sample size, and in some cases unknown prior vaccination status affecting true susceptible population size, and not generalizable to endemic areas. However, these overall findings suggest that persons with measles SVF have a very low risk for transmitting the disease and that in post-elimination settings outbreak-control and public health resources could be prioritized toward vaccine-naive and primary vaccination failure-affected persons. Routine serologic testing for SVF, in addition to the standard PCR tests, may be a useful adjunct for risk stratification during outbreak management.
Reference: Tranter I, Smoll N, Lau CL, et al. Onward Virus Transmission after Measles Secondary Vaccination Failure. Emerging Infectious Diseases. 2024;30(9):1747-1754. doi:10.3201/eid3009.240150.