A vaccine against the parasitic disease malaria cut illnesses by more than half in field trials and could be safely given with other childhood inoculations, two studies have reported. The vaccine, which will begin a third and final phase of clinical trials early next year, could become the first to protect children from malaria, which kills nearly 1 million people worldwide every year.
The studies, published online Monday in the New England Journal of Medicine, were reported at a New Orleans meeting of tropical medicine researchers and were hailed as a significant breakthrough in the fight against one of the most intractable and deadly infectious diseases.
If the phase three trials are successful, it would be "an extraordinary scientific triumph," said Dr. W. Ripley Ballou, deputy director for vaccines and infectious diseases for the Bill and Melinda Gates Foundation, which helped fund the research.
"But more importantly," Ballou added, "it could save millions of children's lives."
Malaria kills nearly 1 million people each year and sickens about 2 million others, according to estimates from the World Health Organization. Most of the deaths are among children younger than 5 in sub-Saharan Africa, the population that the vaccine targets.
The vaccine RTS,S was developed by Belgium-based GlaxoSmithKline Biologicals with support from the PATH Malaria Vaccine Initiative, a global nonprofit consortium that works with pharmaceutical companies.
In the first study, conducted in Kenya and Tanzania, 894 children ages 5 months to 17 months were inoculated either with the three-dose experimental malaria vaccine or a rabies vaccine as a control group. In the eight-month follow-up period, researchers found that children receiving RTS,S had 53% fewer diagnosed cases of malaria -- 38 episodes compared with 86 among recipients of the control rabies vaccine.
In the other study, conducted in Tanzania, the vaccine was given to 340 infants at 8, 12 and 16 weeks old, along with vaccines against polio, diphtheria, tetanus, pertussis (whooping cough) and Haemophilus influenzae B without lessening the safety or effectiveness of the vaccines. The ability to administer the vaccine as part of already established immunization programs is important for countries where health workers, clinics and roads are in such shortage that delivering a drug can be almost as challenging as developing one, researchers say.
Again, the trial was randomized and double-blinded -- considered the scientific gold standard -- with half the infants receiving the malaria vaccine and the other half receiving a hepatitis B vaccine as a control. Although it was not the main object of the study, the researchers found that infants who received the malaria vaccine had 65% fewer infections, as measured by the presence of parasite in the bloodstream, over a six-month period than those who did not, confirming the findings from an earlier, smaller study.
Although half the world's population lives in areas where malaria is transmitted, the disease received little public attention for about 50 years after being eradicated in the United States and Europe. About a decade ago, world leaders called for a renewed effort to fight the mosquito-borne disease caused by parasitic organisms, most seriously Plasmodium falciparum.
In the last few years, widespread distribution of insecticide-treated bed nets and a new combination of medicines have reduced malaria deaths in Ethiopia, Rwanda and Zambia by 50% and more. But because of the threat that Plasmodium falciparum could develop resistance to medications or insecticides, health workers consider a vaccine to be a vital tool. Developing such a vaccine has proven a challenge because the parasite is adept at evading the immune system.
Dr. Carlos C. "Kent" Campbell, who led the malaria program at the national Centers for Disease Control and Prevention for almost 20 years and was not involved in the research, said the findings were impressive.
Larger, clinical trials will continue to test the vaccine on 16,000 infants at 11 sites in Africa. If all goes as planned, the vaccine could be ready for licensure in 2011 and available for use by 2012, Cohen said.