Sometimes, the vaccine is a throw immersion. Take, for example, 97.5% effective Ebola vaccine or 97% effective measles vaccine. Other times, the vaccine is meaningless but offers little or no protection and is clearly intended for the garbage can.
Then there is a third group: the vaccines that fall into the middle. They could protect some but far from everyone. The fate of these vaccines is less secure – in fact an open question.
This is the case with the world's first malarial vaccine, which on Tuesday, April 23, was cautiously added to routine vaccinations in the African country of Malawi as part of a pilot program. Ghana and Kenya will also introduce the vaccine in the coming weeks.
The vaccine, known as RTS, S, is only about 39% effective for preventing malaria – and this is only for children who receive four separate doses. It is only 29% effective to prevent the worst forms of mosquito-borne disease.
However, with more than 200 million worldwide cases of malaria every year and 435,000 deaths, even modest efficiency can result in tens of thousands of lives saved.
"This is the sign of the moment," Kate O'Brien told reporters at a press conference Tuesday. She is the director of the Department of Immunization, Vaccines and Biological Products at the World Health Organization. RTS, S is a "vaccine from the first," she added. This is the first malaria vaccine that shows such efficacy after decades of research and dozens of other candidates. He is the first to reach young, vulnerable children in a routine vaccination program.
RTS, S has been working for more than 30 years. It was created in 1987 in GlaxoSmithKline and works with a malarial parasite protein fragment. Plasmodium falciparumThis fragment causes the immune system to attack when the mosquito delivers the parasite to the blood stream and before the parasite is able to infect the liver. This is where you can ripen, spawn, reappear to infect red blood cells and cause symptoms of disease.
From 2009 to 2014, researchers tested RTS, S in a Phase III clinical trial in seven countries in Africa where 250,000 children die of parasitic infection each year. Data from nearly 15,500 babies and children in the study show that the vaccine is only about 39% effective. It remains to be seen whether the rate of effectiveness will remain in real terms.
Still, with the steep malaria deaths and no other candidates for vaccination on the horizon, public health experts have made the complicated call to recommend RTS S's release after the trials, but they do so with caution. Researchers will carefully follow the pilot vaccination programs in the three countries where they will monitor the efficacy, safety, and how well parents will bring their children to four doses of vaccine. The results will guide policy decisions on whether the vaccine should be used elsewhere in the future.
"We believe that this can be another instrument – an imperfect tool of modest efficiency – just like all our other malaria control tools – but which, when used inadequately, can actually have a huge impact," Pedro Alonso, Director of the Global WHO According to the Malaria Program. Other means used against malaria include indoor insecticide, bed nets and improvements in malaria testing and treatment.
"We are working with a very, very tough organism," Dr. Alonso said, saying about P. falciparum parasites that cause the disease. These are "really complex organisms," he said, and we do not know how long it will take for scientists to invent a better vaccine.
Pilot programs aim to reach about 360,000 children annually in the three countries. It will last for five years, after which public health experts will appreciate the future of RTS, S.