The New York Times published an article today about the encouraging preliminary results of a clinical trial testing a malaria vaccine, known as RTS,S, made by GlaxoSmithKline. The vaccine has been in development for more than 25 years, intitially for the American military and now with most of its support coming from the Bill and Melinda Gates Foundation. The RTS,S vaccine has consistently shown protection against Plasmodium falciparum malaria in children and infants in phase 2 trials. This ongoing phase 3 clinical trial is scheduled to continue through 2014 and will include tests on more than 15,000 children, from infancy on up.
Early results from the trial were released at a Seattle malaria conference today, which showed that three doses protected 47 percent of the 6,000 children ages 5 months to 17 months from severe malaria. I found it interesting that the article mentioned that the age group was chosen because newborns have some protection from their mothers' antibodies, which must be IgG antibodies. While 47 percent protection may not seem very effective with most vaccines not being released until they do better than 90 percent, 47 percent protection would save millions of lives over a decade with malaria estimated to kill about 780,000 people a year, most being African children.
I also found it interesting that the article mentioned it is much more difficult to make a vaccine against a parasite like malaria than to make one against a virus because the malaria parasite changes shape as it moves from blood to liver and back to the blood, with each form having different surface proteins. The actual paper from the New England Journal of Medicine also shows that the vaccine is not without severe adverse events, like convulsive seizures. We may have to wait until 2014 at the conclusion of the trial to see whether the vaccine is effective enough to pay for and if the reduction in malaria outweighs the adverseside effects.
Original Article: The RTS,S Clinical Trials Partnership. (2011). First results of phase 3 trial of RTS,S/AS01 malaria vaccine in African children. The New England Journal of Medicine, 1-13. http://www.nejm.org/doi/full/10.1056/NEJMoa1102287?query=featured_home
Link to The New York Times article: http://www.nytimes.com/2011/10/19/health/19malaria.html?_r=1&ref=health
Great article, after reading this it made me wonder, Plasmodium falciparum which is the plasmodium that causes more fatal and severe disease. Why can't we use other species of plasmodium such as ''Plasmodium vivax'' or ''Plasmodium ovale'' which are milder and less fatal ,compared to Plasmodium falciparum, as vaccinations. Can't we apply the same concept with using cow pox to immunize small pox and use a milder Plasmodium to immunize Malaria?
ReplyDeleteLoved this article when I read it originally in the post.
ReplyDeleteI think one of the biggest challenges though is that some studies have discovered that immunity to malaria only occurs after long exposures to the infection and can even them produce an immunity that is species-specific for that parasite (or at least back in the 70s).
The P. falciparum genome is now fully sequenced and available for researchers which should hopefully help researchers develop a successful species-specific vaccine soon.
My hope is that they can work out the side-effects of the vaccine soon (the convulsions for example) to a less serious degree because the disease is a widespread killer in Africa. The longer time it takes to get out, the more affected populations are by the disease. I don't believe a vaccine should be administered before removing dangerous side effects, but I hope the drug is not kept from people waiting on its protection due to minor set-backs in production or research.
http://www.ncbi.nlm.nih.gov/pubmed/413215
http://www.ncbi.nlm.nih.gov/pubmed/14579459
From PubMed Health I read there are 5 types of malaria. From reading the article it sounds like it will only protect against one type. Do you think it is worth it to create a vaccine with only 47% protective effect against one type of malaria? I am also curious to know why children seem to be more susceptible to malaria than adults. It would be great to create a vaccination against malaria, but it seems like a lot more research needs to be done to prevent the adverse side effects and to increase it's efficacy in the population.
ReplyDeletehttp://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001646/
Great point! The World Health Organization reports four types of human malaria and Plasmodium falciparum to be one of the most common and the most deadly type of malaria. The vaccine tested in the article is against Pasmodium falciparum malaria. Personally, I think it is worthwhile to create a vaccine with 47% effectiveness against the most deadly type of malaria. The article states that while 47% protection is not very effective even that much protection would save millions of lives over a decade.
ReplyDeleteAs far as why children seem to be more susceptible to malaria than adults, the World Health Organization's website says that in Africa where transmission conditions are moderate or intense, adults have built up immunity over years of exposure, and while it never gives complete protection, it does reduce the risk that malaria infection will cause severe disease. For this reason, most malaria deaths in Africa occur in young children who have not built up immunity and there is moderate or intense transmission.