Protective effect of measles vaccine is short-lived in HIV-infected children

By Tom Egwang

The level and longevity of protective antibodies elicited by a measles vaccine is significantly shortened by HIV infection in Zambian children, according to the findings of a prospective study published in the August 1st issue of the Journal of Infectious Diseases.

Measles immunisation programs may have to consider repeated vaccinations in areas of high HIV-1 prevalence.

Measles still remains a significant cause of childhood mortality in sub-Saharan Africa despite the availability of a vaccine.

Barriers to successful measles control by vaccination include poor logistics and insufficient resources, lack of political will, and HIV/AIDS.

HIV infection alters the clinical course of measles in infants: they may not develop the characteristic measles rash and often have a prolonged period of viral shedding.

Children born to HIV-infected mothers are more susceptible to measles because of lower levels of maternally acquired antibodies. HIV-infected children may also respond poorly to measles vaccines and may not maintain protective antibody levels after measles vaccination.

Successful measles control in southern Africa with a high HIV prevalence suggests that the HIV epidemic is not a bottleneck to control.

The determinants of this success must be identified so that it is replicated in other regions. Specifically, how can a high population immunity be achieved in regions with high HIV prevalence so that measles can be eliminated?

Previous studies of the ability of measles vaccines to stimulate antibodies have taken place in developed countries with no escalating HIV problem. There is a shortage of such immunogenicity studies in Africa with co-endemic HIV.

An international team of Zambian, US, and British investigators have addressed this issue in a study of Zambian children. The study took place at the Chawama Clinic in an urban township of Lusaka.

Study subjects were children ages 2-8 months who were enrolled from May 2000 to November 2002 as they visited the clinic for childhood immunisation.

The Edmonton-Zagreb measles vaccine was administered at about 9 months of age to both HIV-1-infected and HIV-1 negative children.

The policy implication is that measles vaccination campaigns must be repeated more frequently in regions of high HIV-1 prevalence.

However, given that effective coverage by the measles vaccine has hitherto been hampered by various reasons, the logistics of repeated vaccinations will be an added constraint.

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