西亚试剂：Poor match

A study published on 21 October revealed2 that the vaccine’s poor performance in clinical trials is in part because it mimics a strain of the malaria parasite Plasmodium falciparum that is not commonly found in Africa.

The vaccine is composed partly of a fragment of circumsporozoite (CS) protein, which is found on the surface of the parasite. Those who are immunized with RTS,S — sold as Mosquirix — build up some immunity to malaria.

But different parasites have slightly different CS proteins — and the study showed that fewer than 10% of parasites infecting some 5,000 children in the trials matched the CS protein sequence in the RTS,S vaccine. If the vaccine could be re-engineered to include bits of several surface proteins, it would be more effective, says Dyann Wirth, an infectious-disease researcher at the Harvard T.H. Chan School of Public Health in Boston, Massachusetts, who led that study.

That re-development could take years, however, although some researchers have been discussing the possibility, according to David Kaslow, who oversees the vaccine’s development at the non-profit health organization PATH. “It’s not trivial to tweak the vaccine to match the prevalent strains in an area,” he told Nature, “but it’s not impossible.”

Hill says that SAGE’s decision to pilot the vaccine sends the right message to other researchers. “Stopping this dead would have been a very bad signal,” he says. “What the field needs is other players to come forward and accelerate their more modern vaccine candidates toward licensure.”

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