Abstract
BackgroundExcept during a 1-year period when BCG vaccine was not routinely administered, annual coverage of infants with Bacillus Calmette-Guérin (BCG) in Kazakhstan since 2002 has exceeded 95%. BCG preparations from different sources (Japan, Serbia, and Russia) or none were used exclusively in comparable 7-month time-frames, September through March, in 4 successive years beginning in 2002. Our objective was to assess relative effectiveness of BCG immunization.Methods/FindingsWe compared outcomes of birth cohorts from the 4 time-frames retrospectively. Three cohorts received vaccine from one of three manufacturers exclusively, and one cohort was not vaccinated. Cohorts were followed for 3 years for notifications of clinical TB and of culture-confirmed TB, and for 21 months for TB meningitis notifications. Prevention effectiveness based on relative risk of TB incidence was calculated for each vaccinated cohort compared to the non-vaccinated cohort.Although there were differences in prevention effectiveness observed among the three BCG vaccines, all were protective. The Japanese vaccine (currently used in Kazakhstan), the Serbian vaccine, and the Russian vaccine respectively were 69%, 43%, and 22% effective with respect to clinical TB notifications, and 92%, 82%, and 51% effective with respect to culture confirmed TB. All three vaccines were >70% effective with respect to TB meningitis.LimitationsPotential limitations included considerations that 1) the methodology used was retrospective, 2) multiple risk factors could have varied between cohorts and affected prevention effectiveness measures, 3) most cases were clinically diagnosed, and TB culture-positive case numbers and TB meningitis case numbers were sparse, and 4) small variations in reported population TB burden could have affected relative risk of exposure for cohorts.Conclusions/SignificanceAll three BCG vaccines evaluated were protective against TB, and prevention effectiveness varied by manufacturer. When setting national immunization policy, consideration should be given to prevention effectiveness of BCG preparations.
Highlights
Since 1921, Bacillus Calmette-Guerin (BCG) vaccine has been given to infants to reduce the risk of tuberculosis (TB) disease, and disseminated TB [1]
In a prospective randomized control trial in Britain in which over 50,000 older children were allocated to no vaccination or one of two vaccine groups, comparable prevention efficacy of 81% to 84% was found among those vaccinated with BCG (Mycobacterium bovis) or with vole bacillus (Mycobacterium microti), respectively, when data were compared over a 20-year period [4]
Because of diagnostic challenges and difficulties inherent in sputum collection in the pediatric population, we examined TB notification data for older children and adults for the years 2002–2007 to determine if reported incidence rates changed in this population, in the event that factors other than changes in BCG vaccine type could account for any changes in incidence observed in the four birth cohorts
Summary
Background Since 1921, Bacillus Calmette-Guerin (BCG) vaccine has been given to infants to reduce the risk of tuberculosis (TB) disease, and disseminated TB [1]. In a prospective randomized control trial in Britain in which over 50,000 older children were allocated to no vaccination or one of two vaccine groups, comparable prevention efficacy of 81% to 84% was found among those vaccinated with BCG (Mycobacterium bovis) or with vole bacillus (Mycobacterium microti), respectively, when data were compared over a 20-year period [4]. In another randomized control trial in India in which over 100,000 uninfected subjects with a normal chest radiograph were allocated to placebo or one of four vaccine groups, no difference was observed in TB incidence among cohorts immunized with a placebo, a low-dose or high-dose Danish BCG strain, or a lowdose or high-dose French BCG strain [5]. Our objective was to assess relative effectiveness of BCG immunization
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