With COVID-19 deflecting attention from TB, new vaccine gives hope for regaining lost ground  

Hopes are pinned on new vaccines to be the game changers in reducing cases and deaths. Until now, the Bacille Calmette–Guérin (BCG) vaccine has been the only licensed vaccine against tuberculosis. But BCG protection does not last against pulmonary TB in adulthood, and because TB disease often occurs years after someone is first infected with TB bacteria, a vaccine which prevents severe TB disease after childhood is needed.

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COVID-19 has slowed down the progress made in confronting tuberculosis (TB). Respiratory clinicians and researchers have had to focus attention away from TB.

COVID-19 has slowed down the progress made in confronting tuberculosis (TB). Respiratory clinicians and researchers have had to focus attention away from TB.

The Conversation – a knowledge resource – reports that the barriers caused by lockdowns and overstretched healthcare systems have had a negative impact on TB diagnosis and treatment. The World Health Organisation reveals that 21% fewer people received care for TB in 2020 compared to 2019.

To make matters worse, potential increases in poverty, undernutrition and long-term lung damage due to COVID-19 are all likely to make many more people vulnerable to TB disease.

Hopes are pinned on new vaccines to be the game changers in reducing cases and deaths. Until now, the Bacille Calmette–Guérin (BCG) vaccine has been the only licensed vaccine against tuberculosis. But BCG protection does not last against pulmonary TB in adulthood, and because TB disease often occurs years after someone is first infected with TB bacteria, a vaccine which prevents severe TB disease after childhood is needed.

In 2019, the new M72/AS01E vaccine caused excitement in the TB field when a trial suggested an efficacy of 50% in preventing TB disease in sub-Saharan Africa. These exciting initial results need to be confirmed in a bigger trial. The pharmaceutical company GSK has licensed the vaccine to the Bill and Melinda Gates Medical Research Institute to lead its further development.

With South Africa and India as scenarios, research findings suggest that the M72/AS01E vaccine could be a very good investment for vaccine developers and health systems, particularly if it is shown to offer protection among TB-uninfected people.

Findings also show that routine vaccination of adolescents could have a huge health impact and be cost-effective in reducing TB deaths and disease. Vaccinating adolescents is key to protect people at the ages when TB is most common.

In India, a vaccine modelled to prevent TB disease regardless of whether someone is already infected with TB bacteria was also highly cost-effective. There was a 92-100% probability of lower cost per DALY averted than the threshold. A vaccine which only protects against progression to TB disease when someone is already infected with TB bacteria was unlikely to be cost-effective (0-6% probability of cost-effectiveness).

So far, the evidence on M72/AS01E efficacy from the trial was only for people previously infected with TB bacteria. It is hoped that efficacy will also be high among people before infection with TB bacteria. But it is likely to be many years before we know whether this is true or not, in part because trials need a huge number of participants.

It is critical to learn from the successes and failures of COVID-19 vaccines.

In countries such as the UK, population-wide COVID-19 vaccination has happened much quicker than anyone working in public health could have dreamt of before the pandemic. Yet in many settings, particularly those most affected by TB, COVID vaccination coverage remains poor. The situation is even worse in the communities most affected by TB.

It is therefore critical to prepare the ground for introducing these vaccines. The first step is speaking to communities and people who will receive them to understand how vaccines can be introduced in a way which meets their needs and preferences.

It’s clearer than ever that continued investment in prevention and care is needed to reach the End-TB goals. Vaccines like M72/AS01E, and other candidates in the pipeline, are likely to be key in the battle to reduce death and disability caused by TB.

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