Why isn’t there a vaccine against malaria?
Vaccines enjoy pride of place in public health. It was the smallpox vaccine, after all, that had wiped out that scourge in the 1970s.
Unlike messy environmental management, land reform, or any number of low-tech options, vaccines are cheap, don’t require health care services, and are a one-shot affair. But developing a vaccine to tame malaria is fraught with obstacles.
Not until 1977 was it even possible to grow the parasite in the laboratory; it had to be harbored and harvested from live animals. Experimental malaria vaccines can’t be tested in animals, who do not sicken from human Plasmodium. They have to be tested on people.
More challenging, a fully effective malaria vaccine must work against 9 radically different forms of the parasite, which vary not only in morphology, but in their physiology as well. Such a vaccine would have to work not just on the four different species of human plasmodium but on the multitude of different strains of the parasite.
Finally, most vaccines are based on triggering an immune response in humans that is known to protect against infection. But there is no human immune response to malaria that protects against infection. The best immune response we have confers only partial protection against serious disease from infection.
For these and other reasons, malaria experts historically have been dubious about malaria vaccine development. When approached about a malaria vaccine program in the waning years of the eradication campaign, the WHO wasn’t interested. Expert malariologists convened by the U.S. AID to consider the idea rejected it as well.
Nevertheless, whether by political calculation or practical misstep, in 1965 U.S. AID launched a $100 million malaria vaccine research program. Some malariologists saw the program less as a strategy to attack malaria than a funding mechanism for lucrative high-tech research. (These “molecular types” are “more concerned with the exquisite intellectual challenges of modish science than with seeking practical solutions,” complained parasitologist Robert S. Desowitz.) Indeed, when New York University scientists funded by USAID developed an experimental biotech malaria vaccine, they promptly patented it and sold the rights to biotech company Genentech.
In 1984, results from clinical trials of the Genentech-USAID malaria vaccine showed that only 2 of 9 vaccinees were protected from Plasmodium. Nevertheless, USAID was optimistic. The vaccine would be ready for “use around the world” within a short five years, the agency announced.
This was surely welcome news to many impoverished malarious countries, deeply indebted to the World Bank and IMF, and under pressure to dismantle malaria control programs. And yet, by 1989, state-run malaria control programs were in shambles, and no malaria vaccine was forthcoming. Malaria vaccine researchers and other contractors funded by USAID were investigated for fraud, theft and criminal conspiracy, and some were indicted.
In 2002, the genomes of the malaria parasite and its mosquito vector were decoded, ushering in a new wave of interest in developing malaria vaccines. Now, the latest tools and techniques can be used to tackle the problem. The Gates Foundation, a philanthropy heavily focused on high-tech solutions to global poverty, funds much of the new malaria vaccine research, which is arguably one of the best funded and most talked about areas of malaria research.
The RTS,S vaccine, while still in clinical development, is currently the most prominent vaccine candidate. In studies to date, the vaccine has shown partial and fleeting efficacy. The vaccine protected seventy-one percent of adults in Gambia from malaria infection for 9 weeks; 6 weeks later, the protective effect vanished to zero. The vaccine delayed infections in less than half of children enrolled in a study in Mozambique. (It reduced the risk of serious disease from malaria infection by about half.) In the most recent study, the vaccine delayed infection for 6 months in less than half of enrolled children. The vaccine prevented infection in just 11 percent of patients, and that for only 6 months.
These equivocal results have not stopped the mainstream press—and the vaccine scientists it quotes—from hailing the promise of the RTS,S vaccine. “New malaria vaccine raises high hopes,” reported the New Scientist. “Hope of malaria vaccine by 2010,” reported the BBC. “Scientists are hailing the findings from a malaria vaccine trial as a huge advance in the fight against the disease,” wrote Nature. (Nature News) “Malaria vaccine is within reach,” National Public Radio headlined.
The RTS,S vaccine, made by GlaxoSmithKline, is a recombinant protein that fuses a part of the P. falciparum circumsporozoite protein with the hepatitis B surface antigen.
For more:
J. Stephenson, “Sequencing of the malaria genome opens door to vaccines and new drugs,” JAMA, March 13, 2002
Judith E. Epstein, “What will a partly protective malaria vaccine mean to mothers in Africa?” Lancet, November 3, 2007-11-16
Robert S. Desowitz, The Malaria Capers: tales of parasites and people (London: WW Norton, 1991)
“The hospital was not a safe place for me.” – malaria patient, Blantyre, Malawi, 2006
