Use of Prefusion F Vaccine in Pregnant Women to Prevent RSV in Infants
It is recommended that women receive certain vaccines during pregnancy that will protect them and their newborn child. The authors of a recent study sought to determine whether the bivalent prefusion F vaccine was beneficial in reducing the burden of respiratory syncytial virus (RSV)-associated lower respiratory tract illness in newborns when administered during pregnancy.
To understand the findings of this study further, Consultant360 reached out to a Pfizer spokesperson to learn more about the study's implications, the clinical impact of the results, and the knowledge gaps that still remain.
Consultant360: How do the results of the study, “Bivalent Prefusion F Vaccine in Pregnancy to Prevent RSV Illness in Infants,” impact clinical practice?
Pfizer spokesperson: This past year has been historic for RSV vaccine development, and we have broken a forty-year spell with no success in developing a vaccine to prevent illness in either older adults or infants. Every year the intensive care units and hospital beds in children’s hospitals fill up because of RSV. Up until this point, doctors still only have one option: using a ventilator for these severe cases.
But what is important here is that we found our vaccine works incredibly well in preventing severe cases through the first 3 months of a child’s life.
Infants are the most vulnerable to infections within the first few months, and we are not able to treat them during this time. And because of this, every year RSV is the number one cause of hospitalizations for babies. However, by immunizing the mother, babies are born with the protection they need.
Our efficacy data from the phase 3 Maternal Immunization Study for Safety and Efficacy (MATISSE) clinical trial for RSV perfusion F has major implications on the future of pediatric care and the overall burden associated with RSV.
If approved, RSVpreF would be the first vaccine for administration to pregnant individuals to help protect against the complications of RSV disease in infants from birth through 6 months of age. The vaccine could be a game-changer in pediatric care and help reduce the severity of the disease in infants.
C360: What stood out from the results of your study?
Pfizer spokesperson: Let me offer a few points from our late-stage study: (1) We found our vaccine was more than 80% efficacious in preventing severe medically attended lower respiratory tract illness, or preventing infants from going to a hospital and for assistance in breathing throughout the first 3 months of the child’s life. We also observed efficacy for infants over the 6-month follow-up period (180 days) was 69.4%; (2) Medically attended severe lower respiratory tract illness occurred within 90 days after birth in 6 infants of women in the vaccine group and 33 infants of women in the placebo group (vaccine efficacy, 81.8%; 99.5% CI, 40.6 to 96.3); 19 cases and 62 cases, respectively, occurred within 180 days after birth (vaccine efficacy, 69.4%; 97.58% CI, 44.3 to 84.1). Hi
Medically attended RSV-associated lower respiratory tract illness occurred within 90 days after birth in 24 infants of women in the vaccine group and 56 infants of women in the placebo group (vaccine efficacy, 57.1%; 99.5% CI, 14.7 to 79.8); these results did not meet the statistical success criterion.
As always, safety is our number one priority for everyone in our trials and anyone who eventually may be immunized. We are thrilled to share there were no serious side effects in any of the pregnant women or in infants and toddlers up to 24 months of age. The incidences of adverse events reported within 1 month after injection or within 1 month after birth were similar in the vaccine group (13.8% of women and 37.1% of infants) and the placebo group (13.1% and 34.5%, respectively).
In May, the U.S. FDA’s Vaccines and Related Biological Products Advisory (VRBPAC) voted in favor of the safety of RSVpreF, Pfizer’s unadjuvanted bivalent RSVpreF vaccine candidate.
C360: Are there still any knowledge gaps that exist in this area of research?
Pfizer spokesperson: We are stopping at the maternal immunization program and our goal is to be able to offer a potential pediatric vaccine candidate. We are beginning a Phase 1 dose escalation and selection study for a pediatric population this year to continue making strides to protect against RSV.
C360: What is the next step in this area of research?
Pfizer spokesperson: If approved, RSVpreF would be the first vaccine for administration to pregnant individuals to help protect against the complications of RSV disease in infants from birth through 6 months. Immunization of pregnant individuals to help protect young infants is also an important strategy to combat other common infant diseases such as neonatal tetanus, diphtheria, and pertussis.
Maternal immunization is a strategy to actively immunize pregnant individuals to passively protect their newborns and young infants during their vulnerable first months of life. In some cases, maternal immunization also is intended to help provide protection to the pregnant individual.
A large body of evidence exists demonstrating safety and effectiveness of currently used vaccines such as influenza vaccine and tetanus-diphtheria-acellular pertussis (Tdap) vaccine in pregnant individuals. These vaccines are regularly included in national routine immunization schedules in many countries such as the United States, Canada, Australia, Europe, and many developing countries worldwide.
To support uptake, Pfizer, along with the medical and public health community, will need to continue to raise awareness about the potential benefits and safety of maternal immunization with expectant individuals and OB/GYNs and Antenatal care providers.
Kampmann B, Madhi SA, Munjal I, et al. Bivalent Prefusion F Vaccine in Pregnancy to Prevent RSV Illness in Infants. N Engl J Med. 2023;388:1451-1464. doi:10.1056/NEJMoa2216480
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