What is the difference between Arexvy and Abrysvo?

Arexvy and Abrysvo are both RSV vaccines (respiratory syncytial virus) that are approved for use in adults over the age of 60 to reduce their risk of developing lower respiratory tract disease (LRTD).

Abrysvo is also approved for use in pregnant women between 32 through 36 weeks gestation, to protect infants against LRTD from the moment they are born until they are 6 months of age. The vaccine is recommended only from September through January, peak RSV season. Arexvy is not approved for use in pregnant women. Arexvy and Abrysvo are not interchangeable for this reason.

Neither Arexvy nor Abrysvo are approved for use in children. Beyfortus is used to protect neonates and infants born during or entering their first RSV season against RSV-caused lower respiratory tract infections. Beyfortus may also be used to protect against RSV-caused lower respiratory tract infections in infants who remain vulnerable through their second RSV season such as those with congenital heart disease or chronic lung disease.

But what are some other differences between them?

Differences in manufacturers and approval dates

• Arexvy is made by GSK and was approved on May 3, 2023; the first RSV vaccine to be approved for older adults.
• Abrysvo is made by Pfizer and was approved on May 31, 2023; the second RSV vaccine to be approved for older adults. It was FDA-approved for pregnant women on August 21, 2023.

Differences in efficacy reporting

The way each company reported on their vaccine's efficacy was different which makes a direct comparison difficult.

• Arexvy showed 94.6% efficacy in reducing the risk of developing RSV-associated LRTD in older adults with underlying conditions, with an overall efficacy of 82.6%.
• Abrysvo showed 67% efficacy in reducing the risk of developing RSV-associated LRTD in older adults with 2 or more symptoms, and 86% efficacy in reducing the risk of developing RSV-associated LRTD in those with 3 or more symptoms. The MATISSE (MATernal Immunization Study for Safety and Efficacy) phase 3 trial reported a vaccine efficacy of 81.8% was observed against severe medically attended LRTD due to RSV in infants from birth through the first 90 days of life with high efficacy of 69.4% demonstrated through the first six months of life.

Warnings

There are no differences in warnings between the 2 products. Neither should be used in people who are hypersensitive to any of the components of either vaccine and neither is approved for use in adults aged less than 60 years or in children. Neither Arexvy nor Abrysvo should be used in children.

Only Abrysvo is approved for use in pregnancy. Arexvy should not be used during pregnancy.

The following warnings are the same for all vaccines:

• Possible anaphylactic reactions
• Possible fainting (syncope)
• Immunosuppressed people may have a diminished response.

Administration

Both Arexvy and Abrysvo are 0.5ml vaccines that are given by intramuscular injection, preferably into the deltoid muscle of the upper arm.

Side effects

Both vaccines are generally well tolerated and side effects are similar and short-lived.

• The most common side effects of Arexvy are injection site pain, fatigue, mild to moderate muscle or joint aches, or headache.
• The most common side effects of Abrysvo are fatigue, headache, injection site pain and redness, and muscle pain.
• Abrysvo has been studied in pregnant women and side effects are similar to those seen in studies with older adults, for example pain at the injection site, headache, muscle pain, and nausea. Preeclampsia occurred in 1.8 percent of pregnant individuals who received Abrysvo compared with 1.4 percent of those who received placebo. Low birth weight and jaundice also occurred at a higher rate in infants of pregnant recipients of Abrysvo versus placebo. Prescribing information for pregnant women will include a warning about a "numerical imbalance" in preterm births in Abrysvo recipients: 5.7 percent versus 4.7 percent in those who received placebo but this data is not sufficient enough to establish that the vaccine can cause preterm births, but provides a warning. This is why the vaccine is only recommended between 32 through 36 weeks gestation.

Vaccination ingredients

The main difference between Arexvy and Abrysvo is in their composition. Arexvy is an adjuvanted vaccine which means it contains a substance that helps to enhance the effects of the vaccine by boosting the response of the immune system. Abrysvo contains no adjuvant, but it is bivalent, meaning that it protects against both RSV A and RSV B. Although Arexvy is technically not bivalent, trials showed it protected against both the A and B strains of RSV. Both need reconstitution before use.

Natural rubber latex is not used in either vaccine.

• The Arexvy vial stopper is not made with natural rubber latex.
• The Abrysvo vial stopper, tip cap, and rubber plunger of the prefilled syringe are not made with natural rubber latex.

Arexvy

Arexvy is an adjuvanted RSV vaccine that is supplied in two vials that must be reconstituted before administration. One vial contains lyophilized recombinant respiratory syncytial virus glycoprotein F stabilized in pre-fusion conformation (rsv vaccine pref3, recombinant systemic) as the antigen component, which must be reconstituted at the time of use with the accompanying vial of GSK’s proprietary AS01E adjuvant as the adjuvant suspension component.

After reconstitution, each dose of Arexvy is approximately 0.5 ml and contains:

• 120 mcg of the recombinant RSVPreF3 antigen, 25 mcg of MPL, and 25 mcg of QS-21.
• The following buffer ingredients: 14.7 mg of Trehalose, 4.4 mg of sodium chloride, 0.83 mg of potassium dihydrogen phosphate, 0.26 mg of dipotassium phosphate, 0.18 mg of polysorbate 80, 0.15 mg of disodium phosphate anhydrous, 0.5 mg of DOPC, and 0.125 mg of cholesterol.

Abrysvo

Abrysvo is a bivalent recombinant stabilized prefusion F protein subunit vaccine that contains equal amounts of stabilized prefusion (preF) antigens from the two major RSV subgroups: RSV A and RSV B (rsv vaccine, pref a-pref b, recombinant systemic). It is supplied as a kit that contains a vial of Lyophilized Antigen Component (a sterile white powder), a prefilled syringe containing the sterile water diluent component, and a vial adapter.

After reconstitution, each dose of Abrysvo is approximately 0.5 mL and contains:

• 120 mcg of RSV stabilized prefusion F proteins (60 mcg RSV preF A and 60 mcg RSV preF B) per 0.5 mL
• The following buffer ingredients: 0.11 mg tromethamine, 1.04 mg tromethamine hydrochloride, 11.3 mg sucrose, 22.5 mg mannitol, 0.08 mg polysorbate 80, and 1.1 mg sodium chloride per 0.5 mL.

Abrysvo contains no preservatives and residual amounts of host cell proteins (≤0.1% w/w) and DNA (<0.4 ng/mg of total protein) may be present from the manufacturing process.