In August 2023 Pfizer announced that the US FDA has approved its vaccine against RSV in infants through immunisation of pregnant individuals. ABRYSVO is a bivalent RSV prefusion F (RSVpreF) vaccine aimed at the prevention of lower respiratory tract disease (LRTD) and severe LRTD caused by RSV in infants from birth up to six months of age. It is approved for use in pregnant individuals from 32-36 weeks gestational age.  


The vaccine is unadjuvanted and comprises two preF proteins that have been selected to optimise protection against RSV A and B strains. It has been demonstrated “safe and effective”. It is a vaccine indicated for: 

  • The prevention of LRTD caused by RSV in people aged 60 and older 
  • Pregnant individuals at 32 through 36 weeks gestational age for the prevention of LRTD and severe LRTD caused by RSV in infants from birth to 6 months old 

In March 2022, Pfizer was granted Breakthrough Therapy Designation by the FDA for ABRYSVO, followed by the FDA’s acceptance of a Biologics License Application under priority review for infants in February 2023. The recent decision by the FDA is based on data from a pivotal Phase III clinical trial called MATISSE (MATernal Immunisation Study for Safety and Efficacy). This was a randomised, double-blinded, placebo-controlled study with results published in The New England Journal of Medicine.  

Two further clinical trials have been initiated to evaluate ABRYSVO. One is being conducted in children at higher risk for RSV disease between the ages of 2 and 18. A second is evaluating adults between the ages of 18 and 60 who are at higher risk for RSV due to underlying medical conditions, and adults aged 18 and older who are immunocompromised and at high-risk for RSV. Post-marketing studies and surveillance programmes are also planned to further describe the safety of the vaccine.  

A significant milestone 

Dr Annaliesa Anderson, Pfizer’s Senior Vice President and Chief Scientific Officer, Vaccine Research and Development, described the approval as a “significant milestone for the scientific community and for public health”, as it is the “first and only maternal immunisation” to protect infants from RSV. She is grateful to the participants of the clinical trial and study investigator teams, as well as colleagues at Pfizer, for their “commitment to making this vaccine available”.  

“Today a long-sought-after goal to deliver a maternal vaccine will help protect infants six months of age or younger – when they are at greatest risk of possible serious consequences from RSV – has been achieved.”  

Dr Eric A.F. Simões, Clinical Professor, Paediatrics-Infectious Diseases, University of Colorado School of Medicine and Children’s Hospital Colorado, Aurora, commented that the approval is a “major triumph”.  

“Newborns and young infants – whose immune systems are still developing and are not yet strong enough to defend against infections – may now be protected from RSV from the moment of birth through maternal immunisation.” 

We look forward to hearing more about our maternal and infant RSV immunisation strategy at The World Vaccine Congress in Barcelona in October. Join us by getting your tickets here, and don’t forget to subscribe to our newsletters for more!