Cell mediated immunity after measles in Guinea-Bissau: historical cohort study.

OBJECTIVE: To investigate whether children who have had measles have reduced general cell mediated immunity three years later compared with vaccinated children who have not had measles. DESIGN: Historical cohort study. SETTING: Bissau, Guinea-Bissau. SUBJECTS: 391 children aged 3-13 years who were living in Bissau during a measles epidemic in 1991 and still lived there. These included 131 primary cases and 139 secondary cases from the epidemic and 121 vaccinated controls with no history of measles. MAIN OUTCOME MEASURES: General cell mediated immunity assessed by measurement of delayed type hypersensitivity skin responses to seven recall antigens. Anergy was defined as a lack of response to all antigens. RESULTS: 82 out of 268 cases of measles (31%) were anergic compared with 20 of the 121 vaccinated controls (17%) (odds ratio adjusted for potential confounding variables 2.2 (95% confidence interval 1.2 to 4.0); P 0.009). The prevalence of anergy was higher in secondary cases (33% (46/138)) than in primary cases (28% (36/130)), although this difference was not significant. Anergy was more common in the rainy season (unadjusted prevalence 31% (91/291) than in the dry season (11% (11/98)) (adjusted odds ratio 4.8 (2.2 to 10.3)). This seasonal increase occurred predominantly in the case of measles. CONCLUSION: Reduced general cell mediated immunity may contribute to the higher long term mortality in children who have had measles compared with recipients of standard measles vaccine and to the higher child mortality in the rainy season in west Africa.

Early BCG vaccination and reduction in atopy in Guinea-Bissau.

BACKGROUND: It has been proposed that certain viral and bacterial infections in early childhood may prevent allergic sensitization, by inducing Th1-type immune responses. This has led to speculation that mycobacterial vaccines might, through their Th1-stimulating properties, also protect against atopy. OBJECTIVE: To investigate whether the prevalence of atopy is lower in children who have been vaccinated with BCG in infancy than in children who have not been vaccinated. METHODS: We measured skin test reactivity to three allergens (Dermatophagoides pteronyssinus, D. farinae and cockroach) in 400 children, aged 3-14 years, as part of a follow-up study to examine the immune sequelae of measles in an urban area of Bissau, the capital of Guinea-Bissau in west Africa. Information on childhood vaccinations, including BCG in infancy, was available from child records. Of these children, 271 had been vaccinated with BCG (according to records) and 53 had not been vaccinated (no record and no BCG scar). Atopy was defined in two ways, according to the presence of any allergen reaction > or = 2 mm and any reaction > or = 3 mm. RESULTS: Of the children who had received BCG vaccine, 57 (21%) were atopic (any reaction > or = 2 mm), compared with 21 (40%) of the unvaccinated children [odds ratio, after controlling for potential confounding factors, 0.19 (95% CI 0.06-0.59)]. When atopy was defined using the 3-mm criterion, the reduction in atopy associated with BCG was greater the earlier the age at vaccination, and the largest reduction was seen in children vaccinated in the first week of life. CONCLUSION: BCG vaccination given early in infancy may prevent the development of atopy in African children.

Measles and atopy in Guinea-Bissau.

BACKGROUND: Epidemiological studies have led to speculation that infections in early childhood may prevent allergic sensitisation but evidence to support this hypothesis is lacking. We investigated whether measles infection protects against the development of atopy in children of Guinea-Bissau, West Africa. METHODS: We conducted a historical cohort study in Bandim, a semi-rural district of Bissau, the capital of Guinea-Bissau. 395 young adults, first surveyed in 1978-80 aged 0-6 years, were followed up in 1994. Our analyses were restricted to 262 individuals still living in Bandim for whom a measles history, documented in childhood, was judged to be reliable. We defined atopy as skin-prick test positivity (> or = 3 mm weal) to one or more of seven allergens. FINDINGS: 17 (12.8 percent) of 133 participants who had had measles infection were atopic compared with 33 (25.6 percent) of 129 of those who had been vaccinated and not had measles (odds ratio, adjusted for potential confounding variables 0.36 [95 percent CI 0.17-0.78], p=O.O1). Participants who had been breastfed for more than a year were less likely to have a positive skin test to housedust mite. After adjustment for breastfeeding and other variables, measles infection was associated with a large reduction in the risk of skin-prick test positivity to housedust mite (odds ratio for Dermatophagoides pteronyssinus 0.20 [0.05-0.81], p=0.02; D farinae 0.20 [0.06-0.71], p=0.01). INTERPRETATION: Measles infection may prevent the development of atopy in African children.