That's because, when administered along withstandard childhood vaccines, the efficacy of RTS,S in infants aged 6 to 12 weeks(at first vaccination) against clinical and severe malaria was 31 percent and37 percent, respectively, over 12 months of follow-up after the third vaccinedose. However, last year the efficacy observed with RTS,S in older children (aged5 to 17 months of age) against clinical and severe malaria was 55 percent and47 percent, respectively.
According to GSK, "follow-up in this Phase IIItrial will continue and is expected to provide more data for analyses to betterunderstand the different findings between the age categories."
"The efficacy is lower than what we saw last yearwith the older 5-17 month age category, which surprised some of us scientistsat the African trial sites," notes Dr. Salim Abdulla, a principal investigatorfor the trial from the Ifakara Health Institute, Tanzania. "It makes us evenmore eager to gather and analyze more data from the trial to determine whatfactors might influence efficacy against malaria and to better understand thepotential of RTS,S in our battle against this devastating disease. We were alsoglad to see that the study indicated that RTS,S could be administered to younginfants along with standard childhood vaccines and that side effects weresimilar to what we would see with those vaccines."
The news comes as a disappointment to investors,of course, and GSK shares fell slightly on the news, but it's also adisappointment to GSK, which had been hoping to have the first effective malariavaccine and now has to step back and re-examine RTS,S a bit.
In 2006, World Health Organization officials said thatany malaria vaccine ideally should cut the risk of severe disease and death byat least half and should have efficacy that lasts longer than a year. As itstands now, malaria kills more than 650,000 people every year, mostly youngchildren and pregnant women in Africa. Without any kind of vaccine to protectpotential victims, the focus has been on insecticide-treated bed nets to keepmosquitoes from spreading the disease and spraying homes with pesticides.
