Epidemiology of a Measles Epidemic in Vietnam 2008-2010

Background. Vietnam conducted a measles catch-up supplementary immunization activity (SIA) during 2002-2003 that targeted children 9 months-10 years of age, followed by subnational SIAs targeting persons up to 20 years of age during 2004 and 2007-2008. A measles epidemic began among young adults in October 2008 in the northern region, spread nationwide during early 2009, and continued during 2010. Methods. We reviewed national epidemiologic and laboratory surveillance data. Measles cases were defined and classified according to World Health Organization recommendations. Results. From October 2008 through January 2010,7948 confirmed measles cases were reported from 60 of 63 provinces, an incidence of 93 cases per million population. Incidence was 328 cases per million population among children age 1-4 years, 318 cases per million population among infants, and 271 cases per million population among persons aged 20-24 years. Few cases were reported among persons 7-17 or >27 years of age. Median age of cases trended downward over time in all regions. Conclusions. The 2002-2003 measles SIA protected its targeted age group, but this epidemic was not prevented by follow-up subnational SIAs in selected provinces during 2007-2008. Transmission began among young adults and was sustained among children. The outcome of Vietnam's 2010 SIA targeting children only and change in routine schedule may influence elimination strategies for other countries.