In a The Lancet Infectious Diseases (Safety and efficacy of PfSPZ malaria vaccine in healthy adults and women attempting to conceive in Mali: two randomized, double-blind, placebo-controlled Phase 1 and 2 trials) A team led by researchers from the Malaria Research and Training Center (MRTC), Bamako, Mali; the Laboratory of Malaria Immunology and Vaccinology (LMIV), National Institute of Allergy and Infectious Diseases, National Institutes of Health; and Sanaria Inc. describes the durable protective effect against malaria demonstrated by Sanaria.^® PfSPZ vaccine when given to women before pregnancy. The two clinical trials, led by Dr. Halimatou Diawara (MRTC) and Dr. Sara Healy (LMIV), were conducted in Ouélessébougou, Mali, from 2018 to 2021. For the first time, immunization with a malaria vaccine was shown to protect mothers against malaria during pregnancy and to protect for two transmission seasons without booster vaccinations.

Malaria during pregnancy is a huge problem. Plasmodium falciparum Infection with PAP (Pf) during pregnancy is estimated to result in up to 50,000 maternal deaths and 200,000 stillbirths in Africa each year.

Better protection for the mother and the developing fetus is urgently needed. The PfSPZ vaccine has an excellent safety profile and our teams have worked with NIH and Sanaria partners over the years to demonstrate its effectiveness in Mali, where seasonal malaria transmission is intense.”

Professor Abdoulaye Djimde, Director of the Malaria Research and Training Centre at the University of Bamako

This study involved women who planned to become pregnant in the coming year. After vaccination, most women stopped using birth control and the women were followed for almost two years through two malaria transmission seasons. Those who became pregnant were followed throughout their pregnancy and newborns were followed until their first birthday to measure long-term effects. The study included two vaccine groups, each receiving low and high doses of the vaccine (100 women per group) and a placebo group that received normal saline (also 100 women).

The PfSPZ vaccine was well tolerated and safe for both mothers and their offspring, with no differences in the frequency or severity of side effects compared with placebo. The vaccine’s effectiveness against malaria parasite infection was as high or higher in the lower dose group in the second year (61%) than in the first year, without a booster – a first for a malaria vaccine. Across the two seasons, effectiveness against malaria parasite infection during pregnancy in this group was 57%. In the high dose group, effectiveness against malaria infection in the first year in women who became pregnant was 86%.

An unexpected finding was that pregnancies were detected earlier in the vaccine group than in the placebo group. Although this effect had little statistical significance, it suggested that malaria infection probably terminates many early pregnancies before they are detected. By preventing these early infections, vaccinated women appeared to become pregnant earlier. This was indeed noted by several mothers: “The vaccine, I love it,” said one participant; “I haven’t had malaria since the study began.” Another participant stated, “I couldn’t get pregnant for three years after I got married, but I got pregnant during the study.”

Alassane Dicko, who leads the team in Mali, said that assessing the effectiveness of the PfSPZ vaccine in women trying to become pregnant was the next logical and ethical step. “We were excited that the vaccine showed significant efficacy against Pf infection not only in the first year but also during a second intense malaria transmission when given before conception. This is a huge step forward in protecting women from malaria before and during pregnancy. We were also surprised to find another positive result, namely that pregnancies developed earlier in vaccinated participants.”

Sanaria Founder and CEO Stephen L. Hoffman, MD, said, “Sanaria’s PfSPZ vaccine has a long and excellent history of safety and tolerability and has demonstrated strong and durable protection against Pf infection in multiple studies in Africa. The results of this study in women of childbearing age clearly demonstrate the potential to save the lives of women and their unborn babies in Africa.” Hoffman believes the vaccine is best given to adolescent girls before pregnancy, who will then receive a booster at the time of pregnancy. All pregnant women who have not yet been vaccinated will receive a full series of immunizations. The next step will be to demonstrate the safety and efficacy of the PfSPZ vaccine in pregnant women.

“Although pregnant women are typically excluded from many clinical trials, given the magnitude of the problem and the profound impact of malaria on women of childbearing age, there is an ethical imperative to develop and test interventions for this vulnerable group,” said Rose Leke, Professor at the University of Cameroon, winner of the 2023 Virchow Prize for Global Health and Chair of the Gavi (Global Alliance for Vaccines and Immunizations) Independent Review Committee. “I welcome the fact that this research team has successfully pioneered the safe testing of the PfSPZ vaccine in young women, achieving promising results in preventing malaria in pregnancy.”