Comparative Tuberculosis (TB) Prevention Effectiveness in Children of Bacillus Calmette-Guérin (BCG) Vaccines from Different Sources, Kazakhstan

Except 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.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.Potential 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.All 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

BCG vaccine prevention effectiveness for TB meningitis cases, Kazakhstan, 2002–2008.

*<p>Risk calculated for the follow-up period specifically used for meningitis cases (21 months).</p>†<p>RR, relative risk; CI, confidence interval; PE, prevention effectiveness.</p

Cohorts of vaccinated and non-vaccinated children in Kazakhstan, 2002–2006.

<p>Cohorts of vaccinated and non-vaccinated children in Kazakhstan, 2002–2006.</p

Relative risk and TB prevention effectiveness of BCG vaccines in different birth cohorts in areas of low (≤2.99/1,000) and high (≥4.02/1,000) reported TB incidence, Kazakhstan, 2002–2008.

*<p>Risk calculated for the entire follow-up period (3 years).</p>†<p>RR, relative risk; CI, confidence interval; PE, prevention effectiveness.</p>§<p>High reported TB incidence - five oblasts: Atyrauskaya, Kyzylordinskaya, Mangistauskaya, West Kazakhstan, and Zhambylskaya. Low reported TB incidence - four oblasts: Almatinskaya, East Kazakhstan, North Kazakhstan, and South Kazakhstan.</p

Survivor curve person-year analyses for reported incidence of active TB among different BCG vaccinated and non-vaccinated birth cohorts, Kazakhstan, 2002–2008.

<p>Survivor curve person-year analyses for reported incidence of active TB among different BCG vaccinated and non-vaccinated birth cohorts, Kazakhstan, 2002–2008.</p

BCG vaccine prevention effectiveness for culture positive TB cases, Kazakhstan, 2002–2008.

*<p>Risk calculated for the entire follow-up period (3 years).</p>†<p>RR, relative risk; CI, confidence interval; PE, prevention effectiveness.</p

Birth cohorts, BCG vaccine used, inclusive months of cohort entry, and length of follow-up, Kazakhstan, 2002–2008.

<p>Birth cohorts, BCG vaccine used, inclusive months of cohort entry, and length of follow-up, Kazakhstan, 2002–2008.</p

Moving average (2-month) TB notification rate of different birth cohorts born in September–March, by type of BCG administered, Kazakhstan, 2002–2008.

<p>Moving average (2-month) TB notification rate of different birth cohorts born in September–March, by type of BCG administered, Kazakhstan, 2002–2008.</p