Pfizer’s Abrysvo Vaccine Receives FDA Approval for Maternal Immunization Against Respiratory Syncytial Virus in Infants
The Food and Drug Administration (FDA) has granted approval for Pfizer’s Abrysvo vaccine to safeguard infants against respiratory syncytial virus (RSV) infections during the first few months of life. This landmark approval allows Abrysvo to be administered during pregnancy, offering a vital shield against RSV to newborns.
Earlier this year, the FDA cleared Abrysvo for use in older adults. The unique feature of this vaccine is its ability to confer immunity to newborns, who are particularly vulnerable to RSV due to their developing immune systems. European regulators also endorsed Abrysvo for use during pregnancy last month.
Peter Marks, head of the FDA’s vaccine review office, expressed the significance of this approval, stating, “This approval provides an option for healthcare providers and pregnant individuals to protect infants from this potentially life-threatening disease.”
RSV is a widespread virus that typically causes cold-like symptoms. However, it can escalate to lower respiratory tract diseases, leading to the hospitalization of tens of thousands of young children each year. It also poses a risk to adults over the age of 60, for whom Abrysvo received FDA approval in May, joining GSK’s pioneering RSV vaccine on the market.
While there are antibody treatments available for young infants, with one gaining FDA endorsement in July, Abrysvo stands alone as a vaccine specifically designed for maternal immunization.
Iona Munjal, executive director of Pfizer’s vaccine clinical research and development, described the significance of this vaccine, stating, “There’s a lot going on in the mom’s life and the baby’s life after birth, and so the ability to just have protection gifted from birth, that’s just really, really magical.”
Developing a safe and effective RSV vaccine has been a decades-long endeavor for drugmakers. The recent approvals for GSK and Pfizer signify a scientific breakthrough in designing improved vaccines, supported by extensive clinical trials in both older adults and pregnant individuals.
Pfizer tested Abrysvo for maternal use in an international trial involving pregnant women between 24 and 36 weeks gestation, who were administered either Abrysvo or a placebo. Subsequently, their babies were monitored post-birth to compare rates of lower respiratory tract illness.
Results, published in The New England Journal of Medicine, indicated that vaccination protected infants from medically attended severe RSV-associated lower respiratory tract illness within 90 and 180 days of birth. However, the study did not meet its goal of demonstrating equally robust protection against milder disease.
Common side effects reported in testing included injection site pain, headache, and nausea among pregnant participants who received the vaccine. A hypertensive disorder called pre-eclampsia occurred in 1.8% of vaccinated participants compared to 1.4% of those given a placebo.
FDA advisors, while discussing the vaccine at a May meeting, noted a potential increase in premature births in lower-income countries. However, the study was not designed to assess this risk accurately, and advisors ultimately voted in favor of the vaccine’s effectiveness and safety.
The FDA’s approval is limited to use between 32 and 36 weeks gestation, a narrower window than Pfizer had originally studied. The agency stated that while the available data do not establish a causal relationship between preterm birth and the vaccine, doctors should avoid vaccinating pregnant individuals before 32 weeks gestation. Follow-up testing is also mandated by the FDA to further evaluate potential risks like preterm birth and pre-eclampsia.
GSK had been developing a maternal RSV vaccine but halted its trial last year after detecting safety concerns. The full details of the study’s results from GSK have not been disclosed.
Now that FDA approval has been secured, an advisory panel to the Centers for Disease Control and Prevention (CDC) will convene to formulate recommendations for the vaccine’s use.
Abrysvo provides expecting parents in the U.S. with another valuable option for protecting their infants, alongside the recently approved monoclonal antibody, Beyfortus, developed by Sanofi and AstraZeneca. Researchers and regulators are currently assessing the safety of administering Beyfortus to newborns whose mothers have been vaccinated with Abrysvo and whether this combination offers additional protection.