When Patrick Duffy He began his career at Walter Reed Military Research Institute in 1991, and scientists had already a few years begun testing the first such vaccine that protected against malaria. Thirty years later, the World Health Organization Finally recommended The outcome of this research as an intervention to control malaria for children under five years of age in Africa. The RTS,S vaccine, also known as Mosquirix, is the first parasite prevention vaccine.
Duffy, now head of the Malaria, Immunology and Vaccine Laboratory at the National Institute of Allergy and Infectious Diseases, is excited about his ability to reduce losses from a disease that kills more than 400,000 people each year. But he is well aware that this vaccine is not a panacea. “This prevents clinical malaria in children,” he says. But it does not stop the transmission of the parasite from mosquitoes to humans, nor does it protect everyone who is at risk. “What about pregnant women? What about exclusion?” he asked. “I feel as though this is a base on which improvements can be made.”
Scientists at pharmaceutical company GlaxoSmithKline (GSK) first created RTS, S in the 1980s, targeting children under five, who represent more than 65 percent of malaria deaths. People develop immunity to the parasite as they age, so adults do not become seriously ill as children if they become infected. This vaccine aims to speed up this process, giving children protection until their immune systems are stronger.
But testing the vaccine took a long time. GSK has partnered with organizations such as Walter Reed, the Bill and Melinda Gates Foundation, and clinics in seven African countries to conduct clinical trials. The European Medicines Agency assessed the vaccine as safe and effective after GSK’s Phase III clinical trials from 2009 to 2011 found it was 50 percent Effective in the prevention of serious disease. But WHO officials remain unconvinced that it will work in a real-world context, because the vaccine requires four doses, delivered as doses, over 18 months. Therefore, GSK ran an additional beta program in 2019, to test the product in Ghana, Kenya and Malawi.
Although every country’s health ministries must approve the vaccine, the WHO’s recommendation is a big endorsement. But scaling up manufacturing to produce millions of doses, organizing national health systems to distribute them, and getting financial aid from nonprofits and other countries takes time. “There is still a lot of work to do before the vaccine is more widely available,” says Ashley Burkett, director of the Malaria Vaccine Initiative at PATH, a nonprofit organization that helped develop the vaccine.
Malaria is a complex parasite that has co-existed with humans for thousands of years. Unlike respiratory viruses like influenza that spread through the air, malaria spreads Spread by mosquitoes. They pick up the parasite from the blood of infected people, then bite others in the community, passing the parasite on to them. While the SARS-CoV-2 virus contains about 10 genes that code for 29 proteins, Plasmodium falciparum, one of five parasites that cause malaria, has a much larger genome that encodes more than 5,000 proteins.
The parasite also has a complex life cycle. When an infected mosquito bites a person, tiny spores called sporozoites enter the bloodstream and travel to the liver, where they begin to multiply by splitting themselves into pieces. These then travel from the liver to the heart, lungs, and bloodstream, where they infect red blood cells and begin giving people flu-like symptoms, nausea, and chills. In severe cases, malaria can cause brain damage, seizures, difficulty breathing, and organ failure.