Is more better? BCG revaccination shows no benefit in Brazil

Many countries routinely vaccinate babies with BCG to prevent tuberculosis (TB). Does a second BCG vaccination give extra protection? Research by Brazil’s Universidade Federal da Bahia in the cities of Salvador and Manaus, shows no added benefit from revaccination of school children aged seven to fourteen years.

Tuberculosis (TB) is one ofthe ten biggest killers in the developing world. Neonatal BCG vaccination provides80 percent protection against TB meningitis but very variable protectionagainst TB disease in the lungs. Revaccination is routine in several countries,mostly in eastern Europe and Asia, and in somemunicipalities in Brazil, although World Health Organization (WHO) globalprogrammes on TB and vaccines do not recommend this. In the past decade, somecountries have decided to stop BCG revaccination, but for economic, not publichealth, reasons.

The researchers assessed theimpact of BCG revaccination on 103,718 children in 386 schools, compared with 97,087children in 375 schools who received no extra vaccine (control group). Afterfive years of follow-up they found that:

• There were 279cases of TB in the study – 144 in the revaccination and 135 in the controlgroup.
• The crudeincidence of TB in the revaccination group was 29.3 per 100,000 person yearsand in the control group was 30.2 per 100,000 personyears.
• The efficacy ofBCG revaccination is nine percent (range -16 to 29 percent).
• The numbers of TBcases involving the lungs versus other organs were similar in both groups.

In summary, revaccinationgiven to children aged seven to fourteen in this setting does not provideadditional protection of public health importance and should not berecommended. The researchers will continue to follow-up the groups to find outwhether:

• revaccinationprotection increases with time since vaccination
• it varies by ageat vaccination
• the first dose ofBCG vaccination at school is protective
• the effect of BCG is the same in cities with low and highlevels of environmental mycobacteria, related to theagent that causes TB.

They also recommend that trialsof new TB vaccines should be planned with regard to issues raised by thisstudy, including duration of vaccine efficacy, potential variation by age andtime since vaccination, and success of passive follow-up of cases. The resultsand recommendations from this study led the Brazilian government to stop itsrevaccination policy in May 2006.