A SOUTH African trial testing the first potential tuberculosis (TB) vaccine in 90 years has found the jab does not protect babies from infection.
The results, published on Monday in the Lancet, are a blow to the field, as the Bacille Calmette Guérin (BCG) shots routinely given to babies around the world provide only limited protection from TB. New tools for stopping the spread of the disease — which has already infected about 2-billion people — are desperately needed and an effective vaccine would be the most powerful way of preventing new infections.
TB is one of the world’s biggest killers, taking the lives of 1.4-million people in 2011, according to the World Health Organisation.
The trial, which was carried out in Worcester by scientists from the South African Tuberculosis Vaccine Initiative (Satvi), tested the safety and efficacy of the candidate vaccine MVA85A in nearly 2,800 babies aged between four and six months living in Worcester in the Western Cape. The vaccine, developed by the non-profit Aeras and the Oxford Emergent Tuberculosis Consortium, is the world’s most advanced potential TB shot.
Scientists had hoped that if they gave a single shot of MVA85A to babies who had already been vaccinated at birth with BCG, it would act as a booster and give them some extra protection. Disappointingly, however, it made no real difference to their odds of getting infected with TB.
The vaccine was well tolerated by the babies.
“While we would have loved to see more protection, we have actually learnt a great deal,” said Ann Ginsberg, Aeras vice-president of scientific affairs, in a telephone interview from the US. “Most importantly, the primary question asked by the trial was is it safe in babies who have already got BCG in a high (TB) burden setting like South Africa, and the answer was ‘yes’ — so that is good news. We also learnt that trials like this can be conducted in a high burden setting to very high standards and that is something that five to 10 years ago people were saying you could not do,” she said.
The trials’ principal investigator, Michele Tameris, said the next step would be to study blood samples collected from the babies more closely and see whether scientists could identify why some babies were able to fend off infection better than others.
“These results don’t in any way jeopardise other trials of MVA85A, and there are many other candidate TB vaccines in the pipeline, so our work goes on,” she said.
Despite its limitations, BCG continues to be used today because it protects babies from some of the most serious forms of TB, which occur outside the lungs and are often difficult to diagnose, she said.
MVA85A is also being studied in a phase-2b trial of HIV positive adults in South Africa and a phase-2a trial in infants born to HIV-positive mothers. The hunt is on for a vaccine that is safe for HIV-positive babies, as BCG — which carries the risk of triggering TB infection — is not ideal for these infants.