Given the challenges of running an efficacy study for a group B streptococcus (GBS) vaccine, Pfizer’s top vaccine executive hopes that regulators will allow an immunogenicity study for approval instead, just as they have for the New York pharma’s meningitis B and pneumococcal vaccines.
That’s according to Annaliesa Anderson, Ph.D., Pfizer’s head of vaccine R&D in a recent interview with Fierce Biotech. Since GBS rates are quite low, she says the company is working on a phase 3 study design that would focus on the product and transfer of antibodies from the mother to the baby.
“Efficacy studies will be extremely large and complicated,” Anderson said, noting that Pfizer’s meningitis B and pneumococcal vaccine were licensed using just serological data.
“And then once they’re licensed, we then do studies to demonstrate the effectiveness,” Anderson said. She added that this is an effective method of getting a vaccine of this type, called a polysaccharide conjugate vaccine, licensed. This type of vaccine wields the same sugar molecules that coat bacteria to help mount a protective immune defense.
It’s unclear how large of a market Pfizer may ultimately be tapping into for the GBS shot. Andersen underscored that the goal remains to gain access to major markets and that she had “not seen a pathway” for any Pfizer vaccine to be developed if its target was not ultimately the U.S. and/or Europe. Prevention guidelines and screening have significantly reduced cases of GBS in the U.S., from about 1.7 per 1,000 live births in 1993 to 0.2 cases per 1,000 live births in 2020, according to the CDC. Anderson says those measures have been less helpful at preventing disease in babies older than a week old.
“And so there’s still important value for this vaccine to be able to potentially prevent disease up to 90 days of life, which is really the window of which you see disease for group B strep.”
The bacterial infection can cause meningitis and bloodstream infections, with 4-6% of babies that contract the disease ultimately dying.
Pfizer’s phase 3 plans follow midstage data released in July showing that the vaccine induced antibody production in pregnant people that transferred to babies. The ratio of antibody transferred from 0.4-1.7 depending on the serotype. The trial recruited 360 healthy pregnant people who received one of three doses, and compared the findings to a parallel natural history study among 18,000 enrolled people who were pregnant. Rates of adverse events were similar following the administration of the vaccine compared to placebo.
The ongoing clinical development has been financially buoyed by grants from the Bill & Melinda Gate Foundation, including $100 million for phase 3 development provided in May 2022. The funding will also help expand access in lower-income countries.