Vitamin A supplementation reduces the morbidity and mortality from acute measles in infants and children in developing countries. Children with low circulating vitamin A concentrations had higher mortality from measles in a study from Kinshasa, Zaire (Markowitz et al., 1989). An early clinical trial from London showed that vitamin A supplementation could reduce mortality in children with acute measles (Ellison, 1932). Clinical trials showed that high-dose vitamin A reduces morbidity and mortality in children with acute measles infection (Barclay et al., 1987; Hussey and Klein, 1990; Coutsoudis et al., 1991; Ogaro et al., 1993). In acute, complicated measles, high-dose vitamin A supplementation (60 mg RE upon admission and the following day) was shown to reduce mortality by up to 80% in Cape Town, South Africa (Hussey and Klein, 1990). Vitamin A supplementation seems to reduce the infectious complications associated with measles immune suppression, such as pneumonia and diarrhoeal disease.

Vitamin A supplementation appears to modulate antibody responses to measles and increases total lymphocyte counts. Children with acute measles infection who received high-dose vitamin A supplementation (60 mg RE upon admission and the following day) had significantly higher IgG responses to measles virus and higher circulating lymphocyte counts during follow-up, compared with children who received placebo (Coutsoudis et al., 1992). When vitamin A supplementation is given simultaneously with live measles vaccine, there appears to be an effect upon antibody titres to measles if maternal antibodies are present. In 6-month-old infants in Indonesia, administration of vitamin A (30 mg RE) at the time of immunization with standard-titre Schwarz measles vaccine interfered with seroconversion to measles in infants who had maternal antibody present, and significantly reduced the incidence of measles vaccine-associated rash (Semba et al., 1995). A separate clinical trial also showed that vitamin A (30 mg RE) reduced antibody responses to measles virus in 9-month-old infants who had maternal antibody present, but did not interfere with overall seroconversion rates to measles (Semba et al., 1997).

In Guinea-Bissau, vitamin A supplementation (30 mg RE) enhanced geometric-mean titres to measles when given simultaneously with standard-titre Schwarz measles vaccine in 9-month-old infants (Stabell Benn et al., 1997). In a two-dose measles immunization schedule at ages 6 and 9 months, simultaneous vitamin A supplementation did not interfere with seroconversion to measles when measured at 18 months of age (Stabell Benn et al., 1997). It was not possible to determine whether vitamin A supplementation interfered with seroconversion rates after measles vaccine in 6-month-old infants in the study in Guinea-Bissau, as with the study in Indonesia, as antibody titres were not measured until after two vaccinations. Although the results of the studies involving 6-month-old infants in Indonesia and Guinea-Bissau have been viewed as contradictory (Ross and Cutts, 1997; Stabell Benn et al., 1997), the differences in the design of the measles-vaccine studies lend little validity to making direct comparisons between these two studies, and the findings may be complementary.

0 0

Post a comment