New waning efficacy data puts GSK malaria shot's future in question

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Researchers already knew that the protection offered by GlaxoSmithKline’s malaria vaccine--the world’s first--wanes over time. But new data shows it may dwindle to nearly nothing sooner than they expected.

After three doses, the effects of the shot--dubbed Mosquirix--are next to nothing after 7 years, scientists say--and what’s more, the decline happens fastest in children living in areas with above-average malaria rates.

The results--published in the New England Journal of Medicine--throw into question whether the jab can actually play a meaningful part in the fight against malaria, researchers said. While in the first year, Mosquirix cut the risk of contracting malaria by 35.9%, after 7 years, that difference was only 4.4%. And after 5 years, among children exposed to higher-than-average malaria rates, the vaccinated group saw 10 more cases than did the control group.

The results don’t come as a complete surprise. Just last year, Phase III data showed a significant drop-off in protection after four years: Among children who received a booster fourth dose of the vaccine, the number of malaria episodes at four years slid by 36%, but without the booster dose, the edge against the disease all but disappeared.

Still, the latest results throw into question whether the jab can actually play a meaningful part in the fight against malaria at all, scientists said. They also suggest that Mosquirix’s implementation “will need to be considered carefully and in a way that takes into account different levels of malaria exposure," according to Mike Turner, head of infections at the Wellcome Trust, which provided a portion of the research funding.

But while the vaccine may not be perfect, it still has the potential to save lives--and it’s that potential that earned it backing last year from the European Medicines Agency. In the most recent study, researchers estimated that Mosquirix averted 317 cases per 1,000 vaccinated children over the 7-year period.

Mosquirix could also “provide an important springboard for improved second-generation vaccines,” Turner told Reuters.

Meanwhile, the World Health Organization has stood by the need to pilot the vaccine before launching wide-scale use. It’s currently working with financing bodies, as well as GSK and the PATH Malaria Vaccine Initiative, to help get the pilots off the ground.

- get more from NEJM
- see Reuters' take

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