First vaccine to prevent RSV in infants by immunizing pregnant individuals now available in Canada

Pfizer is introducing Abrysvo (respiratory syncytial virus [RSV] stabilized prefusion F subunit vaccine) in Canada. It is the first RSV vaccine indicated for the active immunization of pregnant individuals from 32–36 weeks gestational age, to prevent lower respiratory tract disease (LRTD) and severe LRTD caused by RSV in infants from birth through six months of age. The vaccine is also indicated for active immunization of individuals ≥ 60 years of age to prevent LRTD caused by RSV.1,2Action Abrysvo is a bivalent formulation containing two recombinant stabilized RSV prefusion F antigens, each representing the two major virus subgroups, RSV A and RSV B. Following intramuscular (IM) administration, the prefusion F antigens elicit an immune response, which protects against RSV-associated LRTD. Adults 60 years of age and older are protected by active immunization. In pregnant individuals, the neutralizing antibodies are passively transferred from mother to infant.2Dosage Pregnant individuals should receive a single 0.5 mL dose IM in the third trimester of pregnancy (from 32–36 weeks gestation). Individuals ≥ 60 years of age should be given a single 0.5 mL dose IM.2 Administration The lyophilized vaccine must first be reconstituted using the accompanying vial adapter and the diluent provided in a prefilled syringe (consult product monograph for details). The vaccine should be injected IM into the deltoid muscle.2Adverse effects In pregnant individuals and older adults, the most common adverse effects are headache, myalgia and vaccination site pain, redness and swelling. Hypersensitivity reactions have been reported very rarely. Syncope (fainting) is also possible, and may be seen with the administration of other injectable vaccines.2Supplied Abrysvo is available in a 2 mL vial containing a lyophilized powder for solution. The lyophilized antigen component is reconstituted with the sterile water diluent, which is supplied in an accompanying prefilled syringe. Following reconstitution, the vaccine contains 120 µg RSV stabilized prefusion F protein per 0.5 mL.2 Storage/stability Abrysvo should be stored under refrigeration (2°C–8°C) in the original carton to protect from light. After reconstitution, the vaccine should be administered immediately (within 4 hours). The reconstituted vaccine should be kept between 15°C–30°C and should not be refrigerated or frozen.2 Comments Arexvy (RSV vaccine, recombinant, AS01E adjuvanted) was the first RSV vaccine in Canada, marketed by GlaxoSmithKline in the fall of 2023. It is indicated for the prevention of LRTD caused by RSV in adults ≥ 60 years of age.3NACI recommendationsOn May 17, 2024, Canada’s National Advisory Committee on Immunization released a statement on the prevention of RSV disease in infants. The Committee recommends building towards a universal RSV immunization program for all infants.4 NACI recommends that RSV immunization programs use nirsevimab (Beyfortus) to prevent severe RSV disease in infants. Immunization priority should be given to infants who are at increased risk of severe RSV disease in their first or second RSV season. When possible, immunization programs should be expanded to include all other infants entering or born during their first RSV season.4Currently, NACI does not recommend a universal immunization program for Abrysvo. Rather, NACI recommends that Abrysvo can be considered by pregnant individuals, in consultation with their pregnancy care provider, for administration before or during the RSV season, to prevent severe RSV disease in their infant.4 NACI notes that there is no expected additional benefit to using both Abrysvo and nirsevimab for healthy infants. However, if Abrysvo was received during pregnancy and an infant is at increased risk for severe RSV disease, or is born less than two weeks after Abrysvo was given, nirsevimab should still be provided.4 NACI is currently developing recommendations for the use of Abrysvo and Arexvy to prevent RSV in older adults (≥ 60 years of age) and expects a new Advisory Committee Statement on this topic to be published soon.4ReferencesPfizer Canada. Pfizer announces availability of Abrysvo in Canada for immunization of pregnant individuals and adults 60+. May 22, 2024. (accessed May 23, 2024).Pfizer Canada. Abrysvo (respiratory syncytial virus stabilized prefusion F subunit vaccine) product monograph. Kirkland, QC; December 21, 2023. (accessed May 23, 2024).GlaxoSmithKline Inc. Arexvy (respiratory syncytial virus vaccine, recombinant, AS01E adjuvanted) product monograph. Mississauga, ON; August 4, 2023. (accessed May 23, 2024).National Advisory Committee on Immunization (NACI). Statement on the prevention of respiratory syncytial virus (RSV) disease in infants. An Advisory Committee Statement (ACS). (accessed May 23, 2024).

First vaccine to prevent RSV in infants by immunizing pregnant individuals now available in Canada

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