Vaccine with potential to prevent active TB hailed as game-changer

Hyderabad: Touted to be the first in decades, a vaccine has proved effective in preventing dormant tuberculosis from progressing into an active disease among adults, bringing hope that a tool to fight the disease is a possibility. Though it will be years before the vaccine hits the market, international experts have called it a major breakthrough given that a quarter of the world is believed to have latent TB.
Latent TB is where the bacteria is asleep in the body and the person doesn’t have active TB symptoms or illness. The final results of the clinical trial that was published in the New England Journal of Medicine on Tuesday stated that the vaccine (M72/ASO1) has a 50% efficacy rate, or that two doses of the vaccine given a month apart could reduce the number of people with latent TB developing active lung TB by half. The findings, which were presented at the Union Conference held in Hyderabad on Tuesday, also underlined that the vaccine remained effective up to three years. Scientists said that the vaccine mainly works by boosting the body’s antibody levels. Around 30% of the Indian population is estimated to have latent TB.
The stage IIb trial involved 3,573 HIV-negative participants between the ages of 18 and 50 from 11 sites in Kenya, South Africa and Zambia. It found that among those who received the vaccine shots, 13 had developed TB, whereas in the group that didn’t get the vaccine 26 developed TB. “It essentially means that the vaccine has overall efficacy of 50% till three years after vaccination. It means we are preventing one out of two from progressing into active pulmonary TB from its latent form, which is a big step,” said Ann Ginsberg of IAVI, a non-profit research organisation that partnered with GSK to develop the vaccine. She added that the vaccine has shown promise in aspects of safety, reactogenicity and immunogenicity.
“An estimated 10% of those with latent TB go on to get active TB. We are one more cautious, but exciting, step closer to a vaccine for TB,” said Dr Paula Fujiwara, scientific director of The Union, the global body fighting against TB and lung diseases. Calling it a potential tool to fight TB in nearly a century, Dr Thomas Breuer, chief medical officer of GSK vaccines, said that it has taken them 20 years to reach this stage but declined to give a timeline on how soon the vaccine would be available. He also said that more tests are likely to be run to see its efficacy against resistant forms.
Dr Fujiwara said the fact that it will be the first adult TB vaccine, provided it clears the future clinical trials, could be a game-changer. “While the current BCG vaccine for children has been in use for nearly 100 years, its efficacy has come under question owing to the growing TB burden,” said M Hatherhill, one of the researchers.
Experts said currently 15 potential vaccine trials are going on across the world, including a few that will commence in India. “This vaccine has shown the most potential so far though we wait to see other results too,” said Dr Fujiwara.
The Indian Council of Medical Research (ICMR) has launched the first vaccine trial to prevent TB among close contacts of patients. Mumbai’s Sewri TB hospital, which will be a part of the trial, will soon begin recruiting patients.
Diptendu Bhattacharya, a TB survivor, welcomed the development but said that the pace of trials must be expedited.