Gender and the pattern of transmission of measles infection. A reanalysis of data from the Machakos area, Kenya

Is susceptibility to severe infection in low-income countries inherited or acquired?

From a low-income country perspective, we need to emphasize factors which affect acquired susceptibility to severe infection. Such factors may lend themselves to modification by public health interventions. The present paper reviews the experience with understanding the causes of severe measles infection and the impact of health interventions in Guinea-Bissau over a 28-year period. In the 1970s, acquired susceptibility because of malnutrition was considered to be the main cause of high mortality. However, we found no association between nutritional status and subsequent risk of dying of measles. Instead, crowding and intensity of exposure were the main determinants of severe measles. Factors related to transmission have been substantiated for measles, chickenpox, whooping cough and polio. We found measles vaccination to be associated with a major reduction in mortality, particularly for girls. This suggested that measles vaccine has a beneficial nontargeted immune stimulatory effect. The importance of nontargeted effects was clearly documented when World Health Organization introduced a new high-titre measles vaccine (HTMV). HTMV was fully protective but associated with twofold higher mortality for girls. Bacille Calmette Guérin (BCG), diphtheria-tetanus-pertussis (DTP) and oral polio vaccine (OPV) have also shown nontargeted effects, the effect being beneficial for BCG and OPV but negative for DTP. Both beneficial and negative effects are strongest for girls. There are many acquired factors, which affect susceptibility to infection in ways which have not been explored by medical science. They may have a major impact on child survival in low-income countries.

Cytokine profile after rubella vaccine inoculation: evidence of the immunosuppressive effect of vaccination

BACKGROUND AND AIM: Immunization with live virus vaccines may cause an immunosuppression with lymphopaenia, impaired cytokine production and defective lymphocyte response to mitogenes. These abnormalities were described in subjects vaccinated against measles. This study was performed to analyse the host immune response related to immunosuppression in subjects vaccinated with live attenuated rubella vaccine. METHODS: Eighteen schoolgirls, aged 11-13 years, were vaccinated with live attenuated rubella vaccine Rudivax. Before immunization, and 7 and 30 days after, peripheral blood was collected. Cellular fractions were subjected to flow cytometric analysis, and the lymphocyte response to phytohaemagglutinin was investigated. Plasma samples were analysed for cytokines (interleukin (IL)-4, IL-10, tumour necrosis factor-alpha, and interferon-gamma) by enzyme-linked immunosorbent assay techniques. RESULTS: On day 7 after vaccination, the number of each lymphocyte subset was decreased; however, only for CD3 and CD4 lymphocytes has a significant reduction been shown. On the contrary, tumour necrosis factor-alpha and IL-10 levels markedly increased and amounted to its maximum on day 30. Simultaneously, a significant reduction in plasma interferon-gamma and a profound decrease of the lymphocyte response to phytohaemagglutinin were shown. The changes were accompanied with marked elevation of plasma IL-4. CONCLUSIONS: Our data indicate that the vaccination with live attenuated rubella vaccine results in moderate but sustained immune disturbance. The signs of immunosuppression, including defective lymphocyte response to mitogene and impaired cytokine production, may persist for at least 1 month after vaccination.

The global burden of measles in the year 2000--a model that uses country-specific indicators

The estimation of the global burden of measles is challenging in the absence of reliable and comparable surveillance systems worldwide. A static model is described that enables estimation of measles morbidity, mortality, and disability for the year 2000 on the basis of country-specific information (i.e., demographic profile, vaccine coverage, and estimates of case-fatality ratios). This approach estimated a global incidence of 39.9 million measles cases, 777,000 deaths, and 28 million disability-adjusted life years. The World Health Organization regions of Africa and Southeast Asia had 70% of incident cases and 84% of measles-related deaths; 11 countries alone (Afghanistan, Burkina Faso, Democratic Republic of the Congo, Ethiopia, India, Indonesia, Niger, Nigeria, Pakistan, Somalia, Uganda) account for 66% of deaths. This approach quantifies the measles burden by considering country-specific indicators, which can be updated, permitting an assessment of country, regional, and global changes in the burden associated with measles infection.

Functional and phenotypic changes in circulating lymphocytes from hospitalized zambian children with measles

Measles is associated with immunosuppression and increased susceptibility to secondary infections and is a particular problem in developing countries. Lymphocyte changes accompanying immune activation and regulation of the immune response may contribute to immunosuppression. To evaluate lymphocyte changes during measles, children (n = 274) hospitalized with measles in Lusaka, Zambia, were evaluated at entry, discharge, and 1-month follow-up and compared to healthy Zambian children (n = 98). Lymphopenia was present on hospital admission and reflected decreased CD4 and CD8 T cells but resolved quickly. Lymphopenia was most marked in girls, in those with temperatures of >38.5 degrees C, and in malnourished children. CD4/CD8 ratios were decreased at all time points and were lower in boys than in girls at discharge and follow-up. Spontaneous death occurred in cultured lymphocytes, and the proportions of freshly isolated cells undergoing apoptosis, based on annexin V and propidium iodide staining, were increased. Surface Fas was increased on both CD4 and CD8 T cells compared to controls, and expression was greater on CD4 T cells and was inversely correlated with lymphocyte viability in culture at study entry. Mitogen stimulation of lymphocytes improved viability, but inhibitors of Fas, tumor necrosis factor (TNF)-related apoptosis-inducing ligand, and TNF did not. Plasma levels of beta(2) microglobulin and soluble Fas, Fas ligand, CD8, CD4, and TNF receptor were increased, and soluble CD8 was higher in boys than in girls. The multiple effects of measles on lymphocytes from Zambian children include decreased numbers in circulation, increased activation, and increased susceptibility to cell death, with substantive differences in the magnitude of these changes between boys and girls.

Influence of cross-sex transmission on measles mortality in rural Senegal

Previous studies of measles mortality in West Africa have shown a significantly higher case-fatality rate (CFR) among girls than among boys. This study aimed to find out whether the male/female difference in CFR is related to different risks for boys and girls of being infected as secondary rather than index cases and of transmission from someone of the same or the opposite sex. The study was conducted in Niakhar, a rural area of Senegal (population 24,000). All cases of measles reported between March, 1983, and December, 1986, were investigated to determine source of infection and pattern of transmission. For each case, the closest source of infection was judged the most likely. Death was attributed to measles if it occurred within 6 weeks of the onset of rash. Girls had a higher measles CFR than boys (53 deaths/722 cases [7.3%] vs 45/778 [5.8%]); the relative risk of death was 1.30 (95% confidence interval [CI] 0.89-1.90). Secondary cases infected by a child of the opposite sex had a 2.44 (1.48-4.02) times higher risk of death than did secondary cases infected by a child of the same sex. The risk of cross-sex transmission of infection was significantly greater for female than for male secondary cases (1.26 [1.09-1.47]). When this difference in risk of exposure to infection from the opposite sex was taken into account, the difference in risk of death between girls and boys disappeared (1.06 [0.66-1.69]). Within families, the CFR was higher in huts with 1 boy and 1 girl affected than in huts of either 2 boys or 2 girls affected (relative risk 2.16 [0.99-4.70]). Measles infection contracted from a person of the opposite sex is more severe. Variation in exposure may be an important determinant of sex differences in case fatality.