HIV-infected children may require repeat measles
vaccination for protection,
according to new research from the
Johns Hopkins Bloomberg
School of Public
Health and other institutions. The researchers found
that only half the HIV-infected children who survived
without antiretroviral therapy maintained
protective antibody levels 27 months after receiving
measles vaccine. By
comparison, 89 percent of children without HIV maintained
their immunity, as did
92 percent of the HIV-infected children who were
revaccinated in a mass measles
immunization campaign during the 27 months of follow-up.
The study results were
published online June 19 by The Journal of Infectious
Diseases and will be
included in the Aug. 1 printed issue of the journal.
"Despite recent progress in measles control, measles
remains an important
cause of child mortality in sub-Saharan Africa," said
William Moss, lead author
of the study and an associate professor in the Bloomberg
School's Department
of Epidemiology. "The measles virus needs only a small
proportion of susceptible
children to sustain transmission and cause an outbreak.
Vaccinated children with
HIV could be susceptible to measles because of their waning
immunity, impeding
measles elimination efforts in regions with high HIV
prevalence."
The study enrolled more than 690 Zambian children, 2
months to 8 months of
age, who came to the Chawama Clinic in Lusaka, Zambia, for
routine childhood
vaccinations. Within six months of measles vaccination at 9
months of age, 88
percent of HIV-infected children developed protective
measles antibody levels,
as did 94 percent of children born to HIV-uninfected
mothers and 94 percent of
children who did not have HIV but were born to HIV-infected
mothers. The
proportion of HIV-infected children who developed
protective antibody levels was
comparable to those achieved by the other children.
However, 27 months after
vaccination, measles antibody concentrations were 75
percent lower in children
infected with HIV at the time of vaccination and 72 percent
lower in the
children who became HIV infected after vaccination,
compared with HIV-uninfected
children.
The World Health Organization recommends a second
opportunity for measles
vaccination for all children, either through repeated
immunization campaigns or
a routine second dose delivered through the primary health
care system. These
study results suggest that this practice is especially
important in regions of
high HIV prevalence because of waning immunity among
HIV-infected children.
"Sufficient resources must be invested to maintain
high levels of
population immunity against measles in regions of high HIV
prevalence, as well
as investing in strategies to prevent HIV infection and to
treat HIV-infected
people," Moss said.
The study authors also recommend that additional
research be conducted to
determine the duration of measles immunity in HIV-infected
children receiving
antiretroviral therapy and their response to revaccination
against measles.
In addition to Moss, the study was co-authored by
researchers from Johns
Hopkins' Bloomberg School of Pubic Health and School of
Medicine's Division of
Infectious Diseases; Food and Drug Administration; London
School of Hygiene and
Tropical Medicine; and University Teaching Hospital's
Virology Laboratory in
Lusaka, Zambia.
The study was supported by grants from the Wellcome
TrustÐBurroughs Fund
Infectious Disease Initiative and the National Institutes
of Health.