Effectiveness of Early Measles Mumps and Rubella Vaccination among 6-14-Month-Old Infants during an Epidemic in the Netherlands: An Observational Cohort Study.

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J Infect Dis. 2017 Mar 23. doi: 10.1093/infdis/jiw586. [Epub ahead of print]

Effectiveness of Early Measles Mumps and Rubella Vaccination among 6-14-Month-Old Infants during an Epidemic in the Netherlands: An Observational Cohort Study.

Woudenberg T¹ van der Maas NA¹ Knol MJ¹ de Melker H¹ van Binnendijk RS² Hahné SJ¹.

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Abstract

Background.:

Routinely the first measles mumps and rubella (MMR) vaccine dose is given at 14 months of age in the Netherlands. However during a measles epidemic in 2013-2014 MMR vaccination was also offered to 6-14-month-olds in municipalities with <90% MMR vaccination coverage. We studied the effectiveness of the early MMR vaccination schedule.

Methods.:

Parents of all infants targeted for early MMR vaccination were asked to participate. When parent(s) suspected measles their infants saliva was tested for measles-specific antibodies. The vaccine effectiveness (VE) against laboratory-confirmed and self-reported measles was estimated using Cox regression with VE calculated as 1 minus the hazard ratio.

Results.:

Three vaccinated and 10 unvaccinated laboratory-confirmed cases occurred over observation times of 106631 and 23769 days respectively. The unadjusted VE against laboratory-confirmed measles was 94% (95% confidence interval [CI] 79%-98%). After adjustment for religion and siblings vaccination status the VE decreased to 71% (-72%-95%). For self-reported measles the unadjusted and adjusted VE was 67% (40%-82%) and 43% (-12%-71%) respectively.

Conclusions.:

Infants vaccinated between 6 and 14 months of age had a lower risk of measles than unvaccinated infants. However part of the effect was caused by herd immunity since vaccinated infants were more likely to be surrounded by other vaccinated individuals.