Maintaining high rates of measles immunization in Africa
Lessler, J.; Moss, W.J.; Lowther, S.A.; Cummings, D.A.T.
Epidemiology and Infection 139(7): 1039-1049
2011
ISSN/ISBN: 1469-4409 PMID: 20920382 DOI: 10.1017/s0950268810002232Document Number: 581770
Supplementary immunization activities (SIAs) are important in achieving high levels of population immunity to measles virus. Using data from a 2006 survey of measles vaccination in Lusaka, Zambia, we developed a model to predict measles immunity following routine vaccination and SIAs, and absent natural infection. Projected population immunity was compared between the current programme and alternatives, including supplementing routine vaccination with a second dose, or SIAs at 1-, 2-, 3-, 4- and 5-year intervals. Current routine vaccination plus frequent SIAs could maintain high levels of population immunity in children aged <5 years, even if each frequent SIA has low coverage (e.g. ≥ 72% for bi-annual 60% coverage SIAs vs. ≥ 69% for quadrennial 95% coverage SIAs). A second dose at 12 months with current coverage could achieve 81% immunity. Circulating measles virus will only increase population immunity. Public health officials should consider frequent SIAs when resources for a two-dose strategy are unavailable.