Is 12-monthly vitamin A supplementation of preschool children effective? An observational study of mortality rates for severe dehydrating diarrhoea in Yemen

Abstract

Background: Two nation-wide vitamin A supplementation campaigns were launched in the Republic of Yemen. The first (November 1997) targeted children aged 12 - 59 months, and the second (November 1998) targeted the 12 - 59 and the 6 - 11-month age groups. Objective: To document the impact of the two annual vitamin A supplementation campaigns on mortality from severe dehydrating diarrhoea. Design: Observational study. Setting: Four major hospitals in Sana’a, Yemen. Results: The total under-5-year case fatality rate (CFR) was 11% in the pre-dosing year and 8.4% in the first post-dosing year. The reduction was marginally significant (odds ratio (OR) 0.75, 95% confidence interval (CI): 0.56 - 0.99), since only one age group was targeted. CFR in the second year was further reduced to 7.6% (OR 0.67, CI: 0.48 - 0.86), since two age groups were targeted. Among the older than 12-month age groups, the first and second post-dosing year FRs were 4.6% and 5.7%, significantly lower than 11.9% in the pre-dosing year (OR 0.36, CI: 0.25 - 0.5, and OR 0.45, CI: 0.32 - 0.63), respectively. The first 6-month CFR showed a clinically significant reduction, but this was not statistically significant (OR 0.48, CI: 0.16 - 1.35, and OR 0.54, CI: 0.18 - 1.54). Reduction in the last 6 months was statistically significant (OR 0.2, CI: 0.04 - 0.72 and OR 0.38, CI: 0.14 - 0.96), respectively. Among the 6 - 12-month age groups, the first post-dosing year CFR was 8.7%, and 10.1% in the pre-dosing year, a statistically non-significant reduction (OR 0.84, CI: 0.54 - 1.31), since these children were not supplemented in the first campaign. The campaign’s first and last 6 months also showed a non-significant reduction (OR 0.98, CI: 0.51 - 1.91, and OR 0.73, CI: 0.39 - 1.36) respectively. When targeted in the second campaign, CFR was significantly reduced to 4.9% (OR 0.46, CI: 0.32 - 0.66), and 6-month subgroups showed a similar significant trend (OR 0.41, CI: 0.17 - 0.94, and OR 0.49, CI: 0.25 - 0.94), respectively. The under-6-month CFR in the 3-year study period was unchanged (11.4%, 10.1% and 12%). Conclusion. A significant reduction in CFR among children aged 6 - 59 months hospitalised with severe dehydrating diarrhoea was observed following two annual vitamin A supplementations targeting this age group in Yemen.