In an interview with Malaria No More, Dr. Sara Healy, Clinical Trials Director, Laboratory of Malaria Immunology and Vaccinology, US National Institute of Allergy and Infectious Diseases, discusses the results of a recent clinical trial with Sanaria® PfSPZ Vaccine, a groundbreaking new malaria vaccine that was found to offer malaria protections for women during pregnancy.
Can you tell us about the trials?
HEALY: We conducted two trials of the malaria vaccine candidate PfSPZ Vaccine, which is being developed by Sanaria Inc. in Rockville, Maryland. We previously showed the vaccine is well-tolerated and can prevent malaria infections, so we turned next to optimizing the vaccine schedule and dosage so it can be tested in pregnant women, who are very susceptible to malaria.
The first trial began in 2018. It tested whether fewer PfSPZ Vaccine doses delivered over ashorter period than we previously used would still confer protection against natural infection. That study included Malian women and men, ages 18 to 35, who received PfSPZ Vaccine 3 times, delivered either within a single month or spaced over 4 months. Overall, we were encouraged that the shorter schedule was safe and as effective as the longer schedule.
The second trial started in 2019 and included only women in Mali who were planning to get pregnant within a year of entering the trial. Women took contraception during the vaccination period. Afterwards, each woman chose whether to continue or end contraception during the follow up period. We administered PfSPZ Vaccine at two doses using the shorter regimen (3 doses in 1 month) and then we monitored the women through two malaria transmission seasons over nearly two years (2019-2021).
Once again, we found the PfSPZ Vaccine was well-tolerated and safe, including for the women who became pregnant and for their newborns. The vaccine reduced malaria infections in women, including during the time they were pregnant. The vaccine reduced malaria infection during pregnancy by 57% (9x105 PfSPZ Vaccine) or 49% (1.8x106 PfSPZ Vaccine). Among the women who became pregnant during the first season after vaccination, malaria infection was reduced 65% (9x105 PfSPZ Vaccine) and 86% (1.8x106 PfSPZ Vaccine).
We observed that women who received vaccine became pregnant sooner than those who received saline placebo injections. This was an unexpected, but welcome, finding. While the effect did not quite reach statistical significance, it suggests that the vaccine’s ability to prevent malaria infection may help women establish and maintain pregnancies that would otherwise be lost.
The trial results offer hope that a vaccine may be able to protect women against malaria before and during their pregnancy.
Given the success of the trials, what’s next?
HEALY: Our next step will be to show that PfSPZ Vaccine can be safely administered during a woman’s pregnancy. The recently completed trials were like a stepping-stone to prepare us for maternal immunizations. We now have a trial protocol that has been approved by the U.S. and Malian regulatory agencies where we’ve proposed specifically targeting pregnant women for vaccination. If we can identify resources to support this trial, we’d like to start it early next year.
Is it fair to call this a first-of-its-kind malaria vaccine?
HEALY: It is— it’s the first malaria vaccine that will be tested in pregnant women before it is licensed for a general population. It’s the first to be tested before conception as a tool to prevent infections during later pregnancies, and certainly the first to be shown to have this benefit for at least 2 years. I applaud the Sanaria team who are prioritizing malaria interventions for pregnant women—that is an unusual approach but recognizes that women and their babies are dying in alarming numbers due to pregnancy malaria.
Nothing like this exists now?
HEALY: No trials of any malaria vaccine have ever been conducted in pregnant women. So, to have the PfSPZ Vaccine be proven safe for aspiring mothers and their babies is groundbreaking.
For too long, pregnant women have been excluded from trials. But that’s changing. Now, product developers need to have a clear rationale for not including pregnant women in clinical trials. We want expectant mothers to have early access to tools that may improve their health and the health of their newborns. Pregnant women are capable of making an informed choice for themselves and their offspring.
Mindsets are changing. Women deserve to have options that help them and their babies.
What has you most excited about this?
HEALY: I'm not behind one product or another. We should have options when it comes to vaccines for malaria. Besides new drugs and monoclonal antibodies and improved bednets, there are other malaria vaccines in the pipeline that are being evaluated for their potential to protect women of childbearing potential, pregnant women, and their babies.
I’m excited that we are developing an entire tool kit of products for women to choose from. That’s what they deserve. Pregnant women should not be excluded from the best available care and being able to make their own healthcare decisions.
Is expanding protections to pregnant women a necessary step to finally eliminate malaria?
HEALY: It’s a good start! We know adults make a large contribution to malaria transmission within a community. We also know that you can’t exclude pregnant women or women in their childbearing years from malaria elimination campaigns because they're a significant portion of the population.
I believe this study has shifted the mentality of the malaria field and we are now more apt to include pregnant women in clinical trials.
When I went to Mali, I saw women lining up at clinics, coming in for their vaccinations. And they bring their kids with them. Even during the Covid-19 pandemic, these mothers’ main concern was malaria and its impact on their family, their friends, themselves, how many children they subsequently have, whether they've had miscarriages or poor pregnancy outcomes.
So, to witness the excitement and engagement from the community for these trials is pretty amazing!
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