In order to meet India’s goal of eradicating TB by 2025, scientists at the Indian Council of Medical Research have enrolled around 12,000 people in a phase III study of two possible vaccines. The researchers aim to assess how successful the vaccinations are at preventing the disease in adult household members of someone who has just been diagnosed with tuberculosis. Participants from seven Indian sites will be followed for three years before the possible vaccinations are licenced for commercial use or use in the national TB programme.
“Recruitment in the middle of a pandemic was a huge challenge for us because we had to motivate healthy people in a household where TB was detected to come to the DOTS centres for vaccination,” one of the scientists said on condition of anonymity. DOTS, or directly observed treatment, is the name given to the TB control strategy recommended by the World Health Organization.
“For Covid-19 vaccines and therapeutics, the initial results can start coming in within months,” the researhcer said. “But TB is a long-term illness, and we will have to observe the participants for a longer duration to arrive at any result.”
One of the vaccines being tested to prevent tuberculosis of the lungs is Immuvac, which was developed to prevent leprosy. Immuvac, also known as mycobacterium indicus pranii, displays antigens similar to both the leprosy bacterium and the TB bacterium.
The other vaccine candidate is VPM1002, a recombinant BCG that is the most widely used vaccine in the world. The new vaccine developed in Germany has the genetic code of the BCG edited in a way that leads to better availability of the TB antigens, thus training the immune system to better fight tuberculosis.
Another trial of the same candidate is underway to prevent recurrence of TB in adults. VPM1002 is also being tested to see whether it can offer protection against Covid-19.
The BCG vaccine currently in use is a live, weakened form of the bacteria to train the immune system. It is only for use in children. Although it offers protection against the most severe forms of tuberculosis such as TB in the brain, it is not very effective against getting an infection, reactivation of a latent infection, and against the most common form of TB in the lungs. Yet, in the 100 years since the vaccine was developed, there have been no alternatives.
Experts say the government’s push towards eliminating tuberculosis and the formation of a research consortium are the reasons for the focus on TB vaccines.
“Unlike Covid-19 that affected the rich and the poor countries alike, tuberculosis disproportionately affects those in poorer countries and from poorer neighbourhoods,” said Dr DJ Christopher, professor of pulmonary medicine at Christian Medical College in Vellore, and former chair of RePORT India, a consortium for Indo-US collaborative TB research. “There is not enough interest or funding for research of a TB vaccine.”
India’s strategy to eliminate TB hinges on funding 3-4 vaccine candidates for phase I or II trials and have at least one final product co-owned by the government by 2025.
“Studying TB is not very popular. The government’s focus on elimination has certainly helped,” said Dr Pradeep D’Costa, intensivist and head of ICU care at KEM hospital in Pune, where he is heads the trial of VPM1002. “Vaccines will be an important contribution to the programme, but there is still ways to go,”
Even though research into TB vaccines is a step in the right direction, for now the mainstay of the elimination programme is early detection of new cases, testing for drug resistance and treating the disease completely, experts say.