Candidate Malaria Vaccine Provides Lasting Protection

Two NIH-supported trials of an experimental malaria vaccine in healthy Malian adults found that all three tested regimens were safe.

Photo:  Riccardo Mayer/Shutterstock

One of the trials enrolled 300 healthy women ages 18 to 38 who anticipated becoming pregnant soon after immunization. That trial began with drug treatment to remove malaria parasites, followed by three injections spaced over a month of either placebo or the investigational vaccine at one of two dosages. Both dosages of the vaccine candidate conferred a significant degree of protection from parasite infection and clinical malaria that was sustained over two years without a booster dose—a first for any malaria vaccine.

In an exploratory analysis of women who conceived during the study, the vaccine offered significant protection from malaria in pregnancy. If confirmed through additional clinical trials, the approach modeled in this study could open improved ways to prevent malaria in pregnancy.

Malaria parasites such as the species Plasmodium falciparum (Pf) can cause illness in people of any age, but pregnant women, infants and very young children are especially vulnerable. Malarial parasitemia in pregnancy causes an estimated 50,000 maternal deaths and 200,000 stillbirths in Africa each year.  

The trials were co-led by investigators from NIAID and the University of Sciences, Techniques and Technologies, Bamako (USTTB), Mali. The investigational vaccine used in both trials was PfSPZ Vaccine.

In the first year of the current trial, 55 women became pregnant following the vaccination regimen. Vaccine efficacy against parasitemia (before or during pregnancy) was 65% in the low dose group and 86% in the high dose group. Among 155 women who became pregnant across both study years, the lower and higher dose vaccines were 57 and 49% effective, respectively.

“Preconception immunization is a new strategy to reduce [malaria] mortality for women in pregnancy,” the researchers note. They plan to investigate the safety of PfSPZ administered during pregnancy, then examine its efficacy given preconception or during pregnancy in larger clinical trials.