Nothing lasts forever, including BCG vaccine protection for young children

Infants who received BCG [bacille Calmette-Guérin] A meta-analysis found that vaccination at birth had protection against tuberculosis during childhood, but that protection was largely lost in just a few years.

The efficacy of BCG vaccination against tuberculosis in all age groups was 18%.However, when results were stratified by age, infant vaccination showed significant efficacy only in children under the age of five, reported Leonardo Martinez, Ph.D. MPH and his colleagues at Boston University. The Lancet Global Health.

tuberculin skin test and IFNγ release assay A trend toward decreased efficacy with age was also shown by outcome and type of tuberculosis. It was clear that infant vaccination had little or no efficacy until the child reached puberty (although his subgroup findings had very wide 95% confidence intervals to reach firm conclusions). was difficult.)

Overall, this analysis suggests that booster doses may be needed as children at risk for TB get older.

“[T]There is extensive discussion here about the efficacy and duration of protection of the BCG vaccine, and whether the vaccine works only in selective situations. MedPage Today“Our findings show that BCG vaccination is effective in preventing tuberculosis in young children. Continuing BCG vaccination is critical.”

“However, the results show that the vaccine is ineffective in adolescents and adults, so there is a need for increased immune protection in the elderly,” Martinez continued. New vaccines are urgently needed to complement BCG vaccination.”

This meta-analysis is based on case-cohort studies of tuberculosis contacts published between January 1998 and April 2018. Participant-level data were included from 26 cohort studies conducted in 17 countries, yielding a total of 68,552 participants. To be included, an article’s dataset must have a minimum follow-up period of 6 months, individuals with close exposure information regarding age and gender of contact with tuberculosis, study initiation and follow-up dates required was.

Studies were excluded if no information on BCG vaccination was provided or if conducted in a country that does not recommend BCG vaccination at birth (US is not). Individual-level participant data is considered a list of variables including exposed participant (contact) characteristics, index cases, and environment.

Exposure is defined as having close contact (either living in the same household or having substantial interaction outside the home) with a person microbiologically or radiologically diagnosed with pulmonary tuberculosis. it was done.

The primary outcome was a composite of prevalence (diagnosed at baseline assessment or within 90 days) and incidence (new TB cases diagnosed ≥90 days after baseline assessment) tuberculosis cases. Secondary outcomes considered the incidence of pulmonary tuberculosis, extrapulmonary tuberculosis, and mortality.

Data were adjusted for variables of interest, baseline age, sex, previous tuberculosis, and whether data were collected prospectively or retrospectively.The result is the contact age and Mycobacterium tuberculosis infection status.

Martinez and colleagues expressed vaccine efficacy as an odds ratio of infection, comparing vaccinated and exposed individuals to unvaccinated individuals. In many analyses, the odds ratio was close to 1 and often greater than 1 in individuals aged 10 years or older. However, there were no statistically significant results showing that BCG increased the risk of contracting tuberculosis.

Infant vaccination provided significant adolescent protection only for mortality, with an adjusted odds ratio of 0.13 (95% CI 0.04 to 0.41) for 10-14 year olds, which was comparable to efficacy in the younger group. It was the same. However, there was no clear benefit for those 15 years and older (aOR 1.13, 0.35 to 3.68).

The studies used in this meta-analysis were observational in nature and were not randomized. Despite adjustment, there may be residual or unmeasured confounding variables. The BCG vaccine was classified by vaccine scarring, and the absence of scarring could lead to misclassification. Furthermore, mortality analyzes should be interpreted with caution. This is because vaccinated children are of higher socioeconomic status and may have better access to health care. Finally, extrapulmonary tuberculosis is often underreported.

“BCG vaccination was first invented over 100 years ago,” said Martinez MedPage Today“Our findings suggest that its efficacy is overall lacking and is only effective among young children under the age of five. More than 10 million people develop tuberculosis each year. , no new vaccine was available, despite the fact that more than 1 million people have died.”

“New research on new vaccines that can prevent the development of tuberculosis is desperately needed, especially among adolescents and adults,” Martinez added. “Several new vaccines show some promise, but much more funding and work is needed in this area.”