RSV Vaccine Could Prevent Increased Risk of Disease Among Individuals Aged 18 to 59


The results displayed well tolerability and safety with Abrysvo, meeting the study’s co-primary endpoint of immunogenicity and primary safety

Researchers from Pfizer Inc recently announced positive safety and immunogencity findings from MONeT, an ongoing phase 3 clinical trial (NCT05842967), that assessed a single dose of Abrysvo, a respiratory syncytial virus (RSV) vaccine, among individuals at risk of developing severe RSV linked with lower respiratory tract disease (LRTD).

RSV vaccine vial with syringe - Respiratory syncytial virus shot - Image credit: MargJohnsonVA |

Image credit: MargJohnsonVA |

RSV could impact the lungs and breathing passages, which could present as severe infection in a wide range of individuals— including older adults and individuals with certain chronic medical conditions. The study authors noted that annually, RSV accounts for 6000 to 13,000 deaths. However, there 2 subgroups of RSV— RSV-A and RSV-B, which can occur from season to season.

About the Trial ID: NCT05842967

Sponsor: Pfizer

Study Completion (Actual): March 2024

The role of Abrysvo is to provide protection against RSV-LRTD, despite the virus subgroup, according to study authors. The vaccine was previously approved in 2023 by the FDA to treat individuals 60 years and older, along with infants up to 6 months of age. Maternal vaccination of Abrysvo was also approved, the study authors noted.

An increased risk of developing RSV-associated LRTD is linked with individuals that have underlying chronic conditions, like asthma, diabetes, and chronic obstructive pulmonary disease, according to study authors. About 9.5 individuals aged 18 to 49 years residing in the United States have a chronic condition that increases risk of RSV associated LRTD, and individuals aged 50 to 64 years have a 24.3% increased risk. Despite this, there is no current approved RSV vaccine for this age population.

The MONeT study, a phase 3 multicenter clinical trial compared Abrysvo with a placebo, assessing the safety, tolerability, and immunogenicity of the vaccine. The researchers divided individuals with certain chronic medical conditions into substudy A, and immunocompromised individuals into substudy B. The study authors noted substudy A included 681 individuals aged 18 to 59 and were randomly assigned to receive a single dose of Abrysvo or the placebo. Additionally, substudy B included 200 individuals aged 18 to 60 years and older that received 2 doses of Abrysvo approximately 1 month apart.

The results showed the vaccine was well tolerated and safe with Abrysvo, meeting the study’s co-primary endpoint of immunogenicity and primary safety. Neutralizing responses and non-inferior responses were seen in a previous phase 3 Abrysvo study. The study authors noted that the individuals also displayed a 4-fold increase in serum neutralizing titers 1 month after receiving Abrysvo.

“These encouraging results provide evidence that Abrysvo can help protect adults with increased risk against RSV-associated illness,” said Annaliesa Anderson, PhD, senior vice president and head of Vaccine Research and Development at Pfizer, in a press release.

The study authors noted that the MONeT study also met the diversity recruitment goals due to a balanced representation among underlying medical conditions.

“We are excited to address a significant unmet need, pending regulatory authority approval, as Abrysvo has the potential to become the first and only RSV vaccine for adults 18 years and older,” said Anderson in the press release.

Pfizer Announces Positive Top-Line Results from Phase 3 Study of ABRYSVO® in Adults Aged 18 to 59 at Increased Risk for RSV Disease. Pfizer. News release. April 9, 2024. Accessed April 17, 2024.
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