５歳までの小児に、BCGワクチン（Bacille de Calmette et Guérin、結核のワクチン）の２回接種で、死亡率は改善しない。
Effect of revaccination with BCG in early childhood on mortality: randomised trial in Guinea-Bissau
・3,000人弱の患児でプラセボ比較で、死亡率のハザード比は、1.20 (95% confidence interval 0.77 to 1.89)。再接種だけが理由ではないが、むしろ死亡率が増加してしまい、試験は早期に中止。
ObjectiveTo determine whether BCG revaccination at 19 months of age reduces overall child mortality.
DesignRandomised trial, with follow-up to age 5.
SettingA health project in Bissau, Guinea-Bissau, which maintains a health and demographic surveillance system in an urban area with 90 000 inhabitants.
Participants2871 children aged 19 months to 5 years with low or no reactivity to tuberculin and who were not severely sick on the day of enrolment.
InterventionBCG vaccination or no vaccination (control).
Main outcome measureHazard ratios for mortality.
Results77 children died during follow-up. Compared with controls, the BCG revaccinated children had a hazard ratio of 1.20 (95% confidence interval 0.77 to 1.89). Two hundred and fifty children were admitted to hospital for the first time between enrolment and the end of the study, with an incidence rate ratio for BCG revaccinated children versus controls of 1.04 (0.81 to 1.33). The trial was stopped prematurely because of a cluster of deaths in the BCG arm of the study. This increase in mortality occurred at a time when many children had received missing vaccinations or vitamin A or iron supplementation; the hazard ratio for BCG revaccinated children compared with controls was 2.69 (1.05 to 6.88) in the period after these campaigns. Throughout the trial, the effect of BCG revaccination on mortality was significantly different (P=0.006) in children who had received diphtheria-tetanus-pertussis (DTP) booster vaccination before enrolment (hazard ratio 0.36, 0.13 to 0.99) and children who had not received the booster before enrolment (1.78, 1.04 to 3.04).
ConclusionsThere was no overall beneficial effect of being revaccinated with BCG. The effect of BCG revaccination on mortality might depend on other health interventions.