Should HIV-infected children receiving highly active antiretroviral therapy be revaccinated against measles?

Human immunodeficiency virus (HIV)-infected children are at increased risk of measles morbidity and mortality and could play a role in sustaining measles virus transmission in regions of high HIV prevalence. Protective antibody concentrations wane following measles vaccination of HIV-infected children as a consequence of impaired immunity. Until the widespread introduction of antiretroviral therapy, due to the high mortality rate of HIV infected children a sizeable pool of measles susceptible children was not build-up. Highly active antiretroviral therapy (HAART) is effective in prolonging survival in HIV-infected children by suppressing viral replication and restoring immune function. However, immune reconstitution in children is primarily achieved through the generation of naïve T and B lymphoctyes rather than the expansion of memory lymphocytes and antiretroviral therapy does not restore measles vaccine-induced immunity established prior to therapy. As a consequence, HIV-infected children are at increased risk of measles morbidity and mortality despite measles vaccination. In countries with a high prevalence of HIV infection, susceptible children receiving HAART could become sufficiently numerous to sustain measles virus transmission despite high levels of measles vaccine coverage. The 2009 World Health Organization (WHO) position paper on measles vaccines recommended measles vaccination of HIV-infected children who are not severely immunosuppressed and measles vaccine may be administered as early as six months of age in regions of high measles incidence without recommendations on revaccination after immune reconstitution with antiretroviral therapy.