BCG may protect against TB for longer than previously thought: Study
A new study led by the London School of Hygiene & Tropical Medicine found that if administered around 12-13 years, the BCG vaccine protected over 50% of the children in the UK against tuberculosis for at least 20 years.Updated: Sep 01, 2017 14:33 IST
The BCG vaccine, the only one against tuberculosis, could offer protection against the disease for nearly twice as long than previously thought, a new study has found.
The new case-control study led by the London School of Hygiene & Tropical Medicine found that if administered around 12-13 years, the Bacillus Calmette-Guerin (BCG) vaccine protected over 50% of the children in the United Kingdom against tuberculosis for at least 20 years and then waned. It was earlier believed to be effective for 10-15 years.
“Although some studies in countries such as Brazil and Norway have indicated that BCG might be effective for longer than first thought, this study provides the most robust evidence to date,” says the report published in the International Journal of Epidemiology.
With no new tuberculosis vaccine imminently available, the researchers say their findings highlight the important role BCG is playing in preventing the spread of the disease and the need for focussed vaccination coverage in high-risk areas.
In India, BCG vaccine is part of the routine immunisation programme under which about 65% children are fully immunised, about 35% partially immunised and there is still about 7% that don’t get immunised at all.
Tuberculosis is a major, and preventable, cause of death and disease that mainly affects the lungs.
Tuberculosis is less than half as likely to occur in vaccinated children as compared to unvaccinated children 10 to 20 years later, says the report.
“Our study showed it offers moderate protection for longer than had been recognised. This could help countries who are moving towards being ‘low-risk’ areas assess the cost-effectiveness of BCG in the prevention of the disease, and also be a new yardstick against which new TB vaccines in development can be measured,” lead author Dr Punam Mangtani, an associate professor of epidemiology at the London School of Hygiene & Tropical Medicine, said.
BCG vaccine is given in infancy in 158 countries with an estimated 88% coverage overall. Its protective effect can be lower closer to the equator where environmental non-tuberculous mycobacteria or TB infection are more common and, if they occur before vaccination, can mask or block its effect.
Although the World Health Organisation’s End TB strategy highlights the importance of continuing infant BCG vaccination in high prevalence settings, this study suggests it may have a bigger role to play.
“BCG given at school age may help in the control of TB, including reducing the risk of multi drug resistant disease, as those vaccinated around 13 years of age have been protected into adulthood when transmission of the infection was more likely. Health officials should consider recommending childhood BCG vaccination where TB risk is high and where infant vaccination has not been given,” Dr Mangtani said.
“BCG is not perfect but until a new, more effective vaccine is approved and rolled out, we should be maximising its potential. We should also be supporting the various agencies that make sure BCG is readily available.”
Two to three billion of the world’s population is infected with Mycobacterium tuberculosis, 10% of whom progress to clinical disease. An estimated 10.4 million new cases of TB and 1.8 million deaths happened globally in 2015.
In India, 28 lakh new tuberculosis infections are reported in a year and the disease kills an estimated 4.8 lakh people annually.