Preventing Mumps

Measles-mumps-rubella (or MMR) vaccination
typically consists of two doses administered in childhood. Despite these routine vaccinations, mumps
outbreaks are occurring among young adults attending university. The impact of administering a third MMR dose
to improve vaccine effectiveness and control outbreaks is unknown. Since 2012, a 2-dose MMR vaccine has been
a registration requirement for students at the University of Iowa. Investigators analyzed a mumps outbreak between
August 2015 and May 2016 and during this period held 8 mass vaccination clinics on campus
to administer a third dose of MMR. 19,705 students had received two MMR doses before
the outbreak, and 4,783 received a third dose during the outbreak. During the study period, the overall mumps
attack rate was 12.6 per 1,000 population. The mumps attack rate was lower in students
who had received 3 doses than in those who received 2 doses and it was lower among those
who had received two doses within 2 years before the outbreak than among those who had
received two doses 16 to 23 years earlier. As compared with two doses the administration of a third dose of MMR
during the vaccination campaign was associated with a 78% decreased in the risk of mumps. The authors conclude that the risk of
mumps was reduced in students who received a third dose of MMR vaccine, suggesting that
the MMR vaccination campaign improved outbreak control. Full trial results are available at

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