BCG vaccine offers protection from Lung Cancer, reports 60-year follow-up of a clinical trial
In a 60 years follow-up clinical trial, scientists have come up with surprising results which shows that childhood bacille Calmette-Guérin vaccination (BCG)-- used for immunization against tuberculosis (TB)-- may also offer protection from lung cancer. The results were published in the Journal of the American Medical Association (JAMA).
In this 60-year follow-up of a clinical trial of the BCG vaccine that included 2963 participants vaccinated at a median age of 8 years, those who received the BCG vaccine had a subsequent lung cancer rate of 18.2 cases per 100 000 person-years. Participants who received the placebo had a lung cancer rate of 45.4 cases per 100 000 person-years.
BCG vaccine is the only World Health Organization (WHO) approved vaccine indicated for use in infants and children to provide protection against tuberculosis. Apart from its protective role against TB, it has also demonstrated significant immunomodulatory activity in bladder cancer treatment, according to previous studies. However, there are conflicting data as few studies have reported an association of BCG vaccination with increased mortality due to leukemia and lymphoma, particularly non-Hodgkin lymphoma. Other analyses suggested no difference or decreased leukemia incidence and mortality.
To ascertain whether BCG vaccination was associated with cancer rates in a secondary analysis of a BCG vaccine trial, team of researchers conducted a 60 years follow-up clinical trial in which participants were assigned to the vaccine group by systematic stratification by the school
district, age, and sex, then randomized by alternation. The original study was conducted at 9 sites in 5 US states between December 1935 and December 1998.
The trial included 2963 American Indians and Alaska Native schoolchildren younger than 20 years with no evidence of previous tuberculosis infection. Statistical analysis was conducted between August 2018 and July 2019. All the participants were either enrolled to have Single intradermal injection of BCG or saline placebo. Out of 2963 participants, 1540 in the BCG vaccine group and 1423 in the placebo group, remained after exclusions. The main outcome measured were: diagnosis of cancer after BCG vaccination. Data on participant interval health and risk factors, including smoking, tuberculosis infection, isoniazid use, and other basic demographic information were also collected.
Following are key results of the study:
- Vaccination occurred at a median (interquartile range) age of 8 years; 805 participants in the BCG group and 710 in the placebo group were female.
- At the time of follow-up, 97 participants in the placebo group and 106 participants in the BCG vaccine group could not be located; total mortality was 633 participants in the placebo group and 632 participants in the BCG group.
- The overall rate of cancer diagnosis was not significantly different in BCG vaccine vs placebo recipients including for lymphoma and leukemia.
- The rate of lung cancer was significantly lower in BCG vs placebo recipients, controlling for sex, region, alcohol overuse, smoking, and tuberculosis.
Based on the results, the authors conclude,"Childhood BCG vaccination was associated with a lower risk of lung cancer development in American Indian and Alaska Native populations. This finding has potentially important health implications given the high mortality rate associated with lung cancer and the availability of low-cost BCG vaccines."
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