Tuberculosis vaccine does not work

02/06/2013

For decades, researchers have been working to develop a new vaccine against tuberculosis. The previously used BCG (Bacille Calmette-Guérin) vaccine shows too low a protective effect with at the same time a relatively high risk of side effects. The new combination vaccine MVA85A was intended to remedy this, but researchers at Oxford University have now found that MVA85A did not improve the protective effects of BCG vaccination in children.

MVA85A was developed to improve the protective effect of BCG vaccination and was able to achieve very convincing results in initial animal experiments. The researchers around Dr. Michele Tameris of the South African Tuberculosis Vaccine Initiative in South Africa and Professor Helen McShane of the University of Oxford have now published a comprehensive study „Safety, immunogenicity and efficacy of MVA85A against tuberculosis and Mycobacterium tuberculosis infections in infants“ examined and their results in the specialist magazine „The Lancet“ released. The researchers conclude that MVA85A is well-tolerated in children but does not provide additional protection.

Previous tuberculosis vaccine is less effective and has a high risk of side effects
The scientists examined whether the combination of MVA85A and BCG vaccination could improve vaccination in children. The hope was great to have finally found a way against the weaknesses of the BCG vaccine. Because this live vaccine developed from attenuated bovine tuberculosis bacilli only protects against the most serious complications of tuberculosis infections, the so-called miliary tuberculosis and tuberculous meningitis (meningitis). The more widespread, possibly life-threatening pulmonary tuberculosis is not prevented by the vaccine. In Germany, for example, the Standing Vaccination Commission (STIKO) withdrew its recommendation for the BCG vaccine almost 15 years ago, as it does not protect against tuberculosis.

Vaccine was studied on nearly 3,000 South African children
The scientists around Prof. Helen McShane and Dr. med. Michele Tameris, in her double-blind, placebo-controlled study, has now investigated the effect of the new tuberculosis vaccine on 2,797 South African children aged four to six months who had previously received BCG vaccine. 1,399 infants received MVA85A and 1,398 children were given a placebo. The researchers then observed for up to 37 months which protective effect the vaccine had developed and which side effects had occurred. The primary study objective was to verify safety (incidence of adverse and serious adverse events), write McShane and Tameris. The researchers found that, although in the experimental group „more children than in the control group suffered at least one local adverse event, but the number of children with systemic adverse events or serious adverse events did not differ between the groups.“ They therefore assume that MVA85A is well tolerated and does not significantly increase the risk of side effects.

Lack of efficacy of the new tuberculosis vaccine
With regard to the protective effect, the researchers found that the infection risk in the experimental group was similar to that in the control group. The new vaccine has therefore almost no side effects, but also almost no protective effect. To the „Reasons for the lack of efficacy of MVA85A against tuberculosis or M. tuberculosis infections in infants“ the researchers could not provide any further information, but simply emphasized that this requires further research. Despite the disappointing results, today no one can „terminal prognosis for MVA85A or for all other tuberculosis vaccines in development“ be given, writes Christopher Dye of the World Health Organization (WHO) in a commentary on the current „Lancet“-Items. Thus, the search for an improved tuberculosis vaccine remains one of the great challenges of contemporary medical research. (Fp)

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