Clinical studies in young women have shown for the first time that vaccination with a malaria vaccine protects against malaria during pregnancy and continues to protect them for two seasons of transmission without the need for booster doses. New results on the safety and efficacy of the Plasmodium falciparum malaria vaccine (PfSPZ) are published in The Lancet Pathogens.
Malaria
Malaria is a life-threatening disease that is transmitted by certain mosquitoes that carry parasites that cause the disease, which are mostly found in tropical countries. It can be prevented and treated. It is caused by a parasitic organism and is not transmitted from one person to another.
According to the World Health Organization, infants, children under five, pregnant women, travelers, and people with HIV/AIDS are most at risk of severe infection.
There are 5 species of Plasmodium parasites that cause malaria in humans, and two of them (Plasmodium vivax and Plasmodium falciparum) pose the greatest threat, and the latter is the most dangerous and widespread malaria parasite in the African continent.
Malaria and pregnancy
Malaria is a huge problem for pregnant women, with P. falciparum infection during pregnancy resulting in an estimated 50,000 maternal deaths and 200,000 stillbirths in Africa each year.
The results of the study, which verified the safety and efficacy of the Plasmodium falciparum malaria vaccine (PfSPZ), were published in The Lancet on August 14.
The study was conducted by a team led by researchers at the Malaria Research and Training Center (CRTM) in Bamako, Mali, the Malaria Immunology and Vaccine Laboratory, the National Institute of Allergy and Infectious Diseases, National Institutes of Health, and Sanaria Inc. The two clinical trials, led by Dr. Halima Diawara and Dr. Sarah Helvey, ran from 2018 to 2021.
“Better protection for the mother and developing fetus is now essential,” says Professor Abdoulaye Jemdi, Director of the Malaria Research and Training Centre at the University of Bamako. “The P. falciparum malaria vaccine has an excellent safety profile, and our teams have worked with partners at the US National Institutes of Health and Sanaria for years to demonstrate its effectiveness in Mali, where malaria transmission is seasonal and intense.”
Study and Vaccines
The study targeted women who were planning to become pregnant in the year following their participation in the study. After vaccination, contraceptive use was stopped in most cases, and the women were followed during two malaria transmission seasons over a period of approximately two years.
Women who became pregnant were followed throughout their pregnancy, and newborns were followed until their first birthday to measure long-term outcomes. The study included two vaccine groups, one that received low and one that received high doses of the vaccine (100 women in each group) and a placebo group that received normal saline (100 women).
The Plasmodium falciparum malaria vaccine was well tolerated and safe for both mothers and their babies, with no differences in the rate or severity of side effects compared with the placebo group. Vaccine efficacy against malaria parasite infection in the low-dose group was 61% in the second year, an unprecedented achievement for malaria vaccines.
Over the two seasons, the vaccine efficacy against parasitic infections during pregnancy was 57%. In the high-dose group, efficacy against malaria infection was 86% in the first year for women who became pregnant.
unexpected results
An unexpected finding was that pregnancy was detected earlier in the vaccine group than in the placebo group. Although this was not statistically significant, it suggests that malaria infection can lead to miscarriage many times early in pregnancy before it is detected. By preventing this early infection, those who received the vaccine appeared to become pregnant sooner.
“Evaluating the effectiveness of the P. falciparum malaria vaccine in women who wanted to become pregnant was the logical and ethical next step,” says Alsani Dicko, who led the team in Mali. “We were excited to see that the vaccine was highly effective against P. falciparum infection not only in the first year, but also during a second intense transmission season when given before pregnancy. This is a huge advance in protecting women from malaria before and during pregnancy. We were also surprised by the additional positive finding that vaccinated women became pregnant faster.”
The best time to save women and children
“Our P. falciparum malaria vaccine has a long history of safety and excellent tolerability, and has demonstrated strong and durable protection against P. falciparum infection in multiple studies in Africa,” said Dr. Steven Hoffman, founder and CEO of Sanaria. “The results suggest its potential to save the lives of women of reproductive age and their unborn children in Africa.”
The best time to vaccinate adolescents is thought to be before pregnancy, with a booster dose when they become pregnant. A full series of vaccinations will be given to any pregnant woman who has not been vaccinated before. The next step will be to demonstrate the safety and effectiveness of the P. falciparum malaria vaccine in pregnant women.
“Although pregnant women are routinely excluded from many clinical studies, the scale of the problem and the profound effects of malaria in reproductive age impose an ethical obligation on us to design and test drugs and vaccines for this vulnerable group,” says Professor Rose Lake of the University of Cameroon, 2023 Virchow Global Health Prize laureate and chair of the Independent Review Committee of the Vaccine Alliance.