New TB Vaccine stops latent disease becoming active

According to researchers, an experimental vaccine could prevent tuberculosis from developing in half of those who receive it, making it potentially the first new shot against the global killer in a century. It marks a milestone in the fight against TB, although the 54 per cent efficacy rate achieved in adults in a mid-stage clinical trial is low compared to immunizations for other diseases.

The finding is significant as the value of BCG vaccine since its introduction in 1921, has been a subject of continuing controversy. In a large British Medical Research Council trial involving adolescents, the BCG vaccine was 87% protective against disease and 74% protective at 20 years.

Vaccines are one of the most cost-effective interventions to prevent death and debility from infectious diseases. In the case of tuberculosis, there has been widespread scepticism in the scientific community regarding technical feasibility and economic viability of at an effective tuberculosis vaccine.

The new vaccine is designed to stop latent TB from becoming active and causing sickness. According to an estimate, about 1.7 billion people have latent TB infection, putting them at risk of a disease that killed 1.6 million people last year.

The study was conducted in Kenya, Zambia and South Africa. Most of the volunteers had received the BCG vaccine and all were HIV negative. Only 10 of the 1,786 adults vaccinated twice developed active pulmonary TB compared with 22 of the 1,787 given two placebo injection after a mean follow-up of 2.3 years. The vaccine did produce more side effects than placebo, with two-thirds of participants reporting at least one adverse event, typically injection-site reactions or flu-like symptoms.

Results of an ongoing Phase IIb trial of the vaccine - known as M72/AS01 and developed by GSK in conjunction with Aeras, a nonprofit TB group backed by the Bill & Melinda Gates Foundation - were published online by the New England Journal of Medicine.

Mike Turner, head of infection and immunobiology at the Wellcome Trust medical charity, said the encouraging results represented a “landmark moment” and M72/AS01 now needed to be tested in much larger numbers of people.

Tuberculosis is now the world’s largest cause of death from an infectious disease leaving behind human immunodeficiency virus and acquired immunodeficiency syndrome (HIV/AIDS) and malaria. The results of the trial were “ground-breaking” and showed that more effective TB vaccines were achievable to combat this evergrowing health problem of the world.