FDA Approves Pfizer’s RSV Vaccine for Expanded Population of Adults Aged 18 to 59 Years
This new indication for the bivalent respiratory syncytial virus prefusion F vaccine (Abrysvo) makes it the broadest currently available.
Image credit: FDA
The FDA has given the go-ahead to Pfizer for its bivalent respiratory syncytial virus (RSV) prefusion F (RSVpreF) vaccine (marketed as Abrysvo) for the prevention of lower respiratory tract disease (LRTD) caused by RSV in individuals 18 through 59 years of age who are at increased risk for LRTD caused by RSV, according to an announcement by the company.1 This is an extension of the vaccine’s existing indication (which included adults 60 and older), making it the broadest indication for an adult RSV vaccine.
The green light was given based on data from the vaccine’s phase 3 clinical trial, MONeT (NCT05842967), with inference made on the efficacy data available. The trial assessed RSVpreF in adults at risk of RSV-associated disease because of certain chronic medical conditions, including chronic pulmonary (including asthma), cardiovascular (excluding isolated hypertension), renal, hepatic, neurologic, hematologic, or metabolic disorders (including diabetes mellitus).
Alejandro Cané, MD, US vaccine and antivirals lead at Pfizer told Contagion, “RSV is a significant threat to younger adults with certain chronic conditions, such as obesity, diabetes, chronic obstructive pulmonary disease, heart failure, chronic kidney disease, and asthma. In fact, in the US, almost 10% of adults 18 to 49 years of age have an underlying chronic condition that puts them at increased risk of being hospitalized for RSV-associated lower respiratory tract disease. This rises to about 24% of adults with underlying conditions 50 to 64 years of age. With this approval, we are proud that Abrysvo is now the only RSV vaccine indicated for adults aged 18 to 49 at increased risk for the disease, expanding on its existing indications for older adults and pregnant women.” The company additionally noted that it intends to submit results from MONeT for publication in a peer-reviewed scientific journal and for presentation at an upcoming scientific conference.1
In August, Pfizer announced the topline results of MONeT, stating that a single 120-µg dose effectively targets both RSV-A and RSV-B.2 The results were from substudy B of the MONeT trial—which included 203 adults with conditions such as non-small cell lung cancer, end-stage renal disease on hemodialysis, autoimmune inflammatory disorders, and solid organ transplant recipients—and while both 1 and 2-dose regimens were evaluated, the single-dose regimen showed particularly promising results. Safety was deemed consistent with previous studies.
MONeT consisted of 2 substudies: Substudy A, which was a multicenter, randomized, double-blinded, placebo-controlled study of the safety, tolerability, and immunogenicity of RSVpreF in adults 18 to 59 years of age considered to be at high risk of RSV disease due to certain chronic medical conditions; and Substudy B, a single-arm, open-label, multicenter study of the safety, tolerability, and immunogenicity of RSVpreF in immunocompromised adults.
In April 2024, Pfizer announcer initial results from the trial,3 noting that the vaccine had met the primary end points of the study, most notably that participants in Substudy A and Substudy B subgroups demonstrated neutralizing responses that were noninferior to the response seen in the phase 3 RENOIR study (NCT05035212) of Abrysvo in more than 34,000 adults aged 60 or older where vaccine efficacy was previously demonstrated.
In that update, study participants also reported at least a 4-fold increase in serum neutralizing titers for both substudies after 1 month post vaccination compared with pre-vaccination. During the trial, Abrysvo was well-tolerated, and safety findings were consistent with those from previous investigations of Abrysvo in other populations.
In 2023, the vaccine was approved for the infants from birth to 6 months indication,4 based on data from the pivotal, randomized, double-blind, placebo-controlled phase 3 clinical trial MATISSE, which evaluated efficacy, safety, and immunogenicity of the vaccine against LRTD and severe LRTD because of RSV in infants born to healthy individuals who were vaccinated during pregnancy. The trial, which was conducted in 18 countries over 4 RSV seasons, followed infants for up to 2 years. Overall, 3682 maternal participants aged 49 years or younger, at 24-36 weeks’ gestation on the day of planned RSVpreF injection, received a single intramuscular injection of 120 μg of RSVpreF vaccine and 3676 received placebo, with investigators subsequently evaluating 3570 and 3558 infants, respectively.3,4
Recently, at IDWeek 2024, Contagion connected with Elliot DeHaan, MD, the director of vaccines clinical research and development at Pfizer, and lead clinician on the MONeT study. He highlighted the significant findings, saying that “these individuals had similar immune responses to adults 60 and older who were enrolled in the RENOIR trial in which we demonstrated efficacy of that vaccine. This technique is called immuno-bridging, and what we can confer from that immuno-bridging result is that we expect the immune response to be the same in these individuals.”
DeHaan also discussed the safety profile of the vaccine observed in the trial, particularly for the high-risk population, “the most common solicited local reaction in our Substudy A was pain at the injection site, reported by around 35% of vaccine recipients. The 2 most common systemic solicited events were fatigue and headache. These results were very similar to those in other trials, indicating consistent tolerability and safety.”
Check out the video below for more of DeHaan's thoughts.
