10:21am Wednesday 13 November 2019

Failure to protect infants does not mean the end for new TB vaccine

Lung tissue stain with TBThe world’s most advanced tuberculosis (TB) vaccine has failed to protect babies against the disease, despite earlier successes stimulating high levels of immune response in adults, according to a new efficiency trial.

The MVA85A vaccine was designed to provide more effective protection than the current BCG, the only existing vaccine used to prevent TB.  The new results, announced this week, showed that although the vaccine appeared to be safe, it did not provide extra protection against TB in infants who had already received the BCG vaccine.

Co-authoring a comment in the Lancet on the findings, Professor Paul Fine describes the search for an improved TB vaccine as one of the “great quests of contemporary medical research”.  Although he admits that the new findings among infants are disappointing and present a serious challenge to the TB vaccine community, he argues that it is not a “terminal prognosis” for MVA85A or for other vaccines in development.

Professor Fine writes that there are still several questions that need to be answered before drawing any firm conclusions about the vaccine, including whether a booster of MVA85A might protect adolescents and adults against pulmonary tuberculosis in a way that it cannot protect infants, and how the vaccine might work if administered to people infected with HIV.

Professor Fine concludes: “Now is a key moment in tuberculosis vaccine research. Trials… are at last generating hard evidence about protection against tuberculosis in human beings, the most important goal of immunisation. If the history of tuberculosis vaccine research teaches us anything, it is to expect surprises. We need to go on playing the high-stakes game.”

Dr Richard White, an epidemiologist at the London School of Hygiene & Tropical Medicine and Director of the TB Modelling and Analysis Consortium, says: “This is a very disappointing result, but this was just the first of around 12 new tuberculosis vaccines currently being tested in humans and around 50 vaccine candidates currently being tested in the lab. It was a historic trial, the first of a new TB vaccine for nearly a century. It will lead to much valuable knowledge to help us design effective vaccines in the future.

“The impact of TB on men, women and children is huge. TB kills around 1.4 million people a year costs us around a billion dollars a day. Preliminary modelling suggests that even a partially effective vaccine could have a major impact on men, women and children whose lives are currently blighted by TB, averting millions of TB cases and deaths over 25 years.”

Image: Stained lung tissue showing presence of Mycobacterium tuberculosis bacelli. Credit: Maria Podinovskaia

London School of Hygiene & Tropical Medicine

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