October 29, 2019
2 min read

Experimental TB vaccine could have ‘vast’ impact

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An experimental vaccine against Mycobacterium tuberculosis was nearly 50% effective in protecting infected adults from progression to pulmonary tuberculosis disease for at least 3 years, according to study findings published in The New England Journal of Medicine.

The vaccine candidate, M72/AS01E, is being developed by GlaxoSmithKline.

“These results demonstrate that for the first time in almost a century, the global community potentially has a new tool to help provide protection against TB,Thomas Breuer, MD, MSc, chief medical officer of GSK Vaccines, said in a news release.

In the study, Dereck R. Tait, MB, ChB, from the International AIDS Vaccine Initiative (IAVI), and colleagues noted that TB remains the world’s top infectious disease killer, and that WHO has said new TB vaccines should be at least 50% effective against bacteriologically confirmed TB for at least 2 years.

Mycobacterium tuberculosis  
An experimental vaccine was around 50% effective in protecting infected patients against active TB.
Source: National Institute of Allergy and Infectious Diseases.

“These final results show that M72/AS01E could be an important tool in the fight against pulmonary tuberculosis,” IAVI president and CEO Mark Feinberg, MD, PhD, said in the release. “While additional trials need to be conducted to confirm these findings in other populations, we have never before seen a vaccine that provides protection in adults who are already infected with the bacteria that cause tuberculosis.”

A previous placebo-controlled, phase 2b trial of M72/AS01E showed that it was 54% effective after about 2 years in preventing active TB in HIV-negative adults with latent M. tuberculosis infection. In the final analysis, Tait and colleagues aimed to determine the efficacy, safety and immunogenicity of M72/AS01E after 3 years.

Between August 2014 and November 2015, researchers enrolled TB-infected adults aged 18 to 50 at centers in Kenya, South Africa and Zambia, and randomly assigned them 1:1 to receive two doses of either M72/AS01E or placebo, administered 1 month apart. According to the study, participants were followed for 3 years after the second dose.

Analysis showed that 13 of the 1,626 participants in the M72/AS01E study arm had cases of TB that met the definition of a first case, compared with 26 of the 1,663 participants in the placebo group — an incidence of 0.3 cases vs. 0.6 cases per 100 person-years, respectively. According to Tait and colleagues, vaccine efficacy at month 36 was 49.7% (90% CI, 12.1%-71.2%; 95% CI, 2.1%-74.2%). Additionally, the researchers found that among participants who received M72/AS01E, the concentrations of M72-specific antibodies and the frequencies of M72-specific CD4+ T cells increased after the first dose and were sustained throughout the follow-up period.

The results are “impressive,” said Barry R. Bloom, PhD, the Joan L. and Julius H. Jacobson Research Professor of Public Health at the Harvard T.H. Chan School of Public Health.

“This is the first vaccine that has ever shown protection in previously M. tuberculosis-infected individuals and so offers the potential for protection of vast numbers of people in endemic countries,” Bloom told Infectious Disease News. “Even if only 50% effective, with 10 million new cases and 1.4 million deaths, the number of lives that could be saved would be great, if it worked in different populations and in uninfected individuals as well as it did in South Africa.” – by Caitlyn Stulpin

Disclosures: Bloom reports serving as an editor for the Proceedings of the National Academy of Sciences of the United States of America for a manuscript that reported the effectiveness of M72/AS01E in nonhuman primates and serving as an external reviewer of the South African TB Vaccine Initiative (SATVI) in 2015. Breuer is employed by GSK. Feinberg is the CEO of IAVI. Tait reports receiving grant funding from the Bill and Melinda Gates Foundation, DFID, DGIS and AusAid. Please see the full study for all other authors’ relevant financial disclosures.