Pfizer’s RSV Vaccine Abrysvo Is a New Step for RSV Prevention

Pfizer’s RSV Vaccine Abrysvo Is a New Step for RSV Prevention

Pfizer’s Abrysvo is now the second RSV vaccine to win FDA approval.

Pfizer has announced that its respiratory syncytial virus (RSV) vaccine, Abrysvo, has received approval from the US Food and Drug Administration (FDA). Abrysvo, the bivalent RSV prefusion F (RSVpreF) vaccine, is intended for the prevention of lower respiratory tract disease (LRTD) caused by RSV in individuals aged 60 years and older. Abrysvo is an unadjuvanted vaccine and is composed of two preF proteins selected to optimize protection against RSV A and B strains.

“A vaccine to help prevent RSV had been an elusive public health goal for more than half a century. Today’s approval is a monumental step forward in delivering on Pfizer’s commitment to help alleviate the significant burden of RSV in higher-risk populations, which includes older adults,” said Annaliesa Anderson, PhD, senior VP and chief scientific officer, Vaccine Research and Development at Pfizer, in the company’s news release.

In February 2023, Pfizer revealed that the European Medicines Agency (EMA) has accepted the Marketing Authorization Application (MAA) for Abrysvo. The application, aimed at RSVpreF, is intended for both older adults and maternal immunization to protect against RSV and is under accelerated assessment. Pfizer also announced that an application has been filed with Japan’s Ministry of Health, Labor and Welfare for RSVpreF as a maternal immunization, with the goal of protecting infants from RSV.

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What is Respiratory Syncytial Virus (RSV)?

RSV is a highly contagious virus that can cause respiratory infections, including bronchiolitis or pneumonia, in individuals of all ages. Symptoms of RSV infection are similar to the flu, such as coughing, sneezing, runny nose, fever and wheezing. While most people usually recover within a few weeks, infants and older adults are at a higher risk of developing severe complications.

According to the US Centers for Disease Control and Prevention (CDC), annually, RSV causes between 60,000 to 120,000 hospitalizations and results in 6,000 to 10,000 deaths among adults aged 65 and above in the US.

RSV belongs to the family of negative-strand RNA viruses and was first identified in 1955. The virus spreads through droplets or direct contact and targets the epithelial cells of the respiratory mucosa, leading to lower respiratory tract infections, bronchiolitis or pneumonia.

Research indicates that RSV can interfere with the functioning of dendritic cells, vital for initiating an antiviral response. This interference may reduce the antiviral T-cell response or, in some cases, trigger the activation of unwanted pro-inflammatory T-cells, thus increasing the risk of severe lung infections.

How Does Abrysvo Work?

The genetic material of RSV (respiratory syncytial virus) encodes 11 proteins. Among these, the type I integral membrane fusion protein, also known as the F-protein, is crucial for the pathogenesis of RSV. The F-protein facilitates the fusion of the virus with the membrane of the host cell.

The F-protein of the virus, before interacting with a cell, assumes a lollipop-shaped structure referred to as the prefusion confirmation (preF), which is visible on the surface of the virus.

Abrysvo functions as a vaccine by triggering an immune response specifically aimed at RSV preF, which provides protection against RSV-induced LRTD.

Pfizer's RSV Vaccine Vials of Abrysvo
Vials of Pfizer’s RSV vaccine. Photo courtesy of Pfizer.
Pfizer's RSV vaccine filling of Abrysvo
Pfizer’s RSV vaccine fillings. Photo courtesy of Pfizer.







Safety and Efficacy of Abrysvo

The FDA’s approval of Abrysvo is supported by compelling clinical evidence. In a global, randomized, double-blind, placebo-controlled Phase III study with approximately 37,000 participants, Abrysvo exhibited a vaccine efficacy of 66.7 percent against RSV-associated lower respiratory tract illness with at least two signs or symptoms, and 85.7 percent efficacy against this illness with at least three signs or symptoms.

The clinical study also revealed the favorable tolerability of Abrysvo. Common side effects included injection site pain, redness, swelling, fever, fatigue, headache and muscle pain. Local reactions were more common with the vaccine (12 percent) than with the placebo (seven percent), while systemic event rates were similar for both groups (27 percent and 26 percent, respectively).

“Today’s FDA approval of Abrysvo recognizes significant scientific progress, and importantly helps provide older adults potential protection against RSV and an opportunity to improve community health by helping prevent the disease,” said Edward E. Walsh, MD, professor of medicine, University of Rochester Medical Center, and principal study investigator, in the company’s news release.

What is the Price of Abrysvo?

The exact cost Abrysvo has not been publicly disclosed at this time; however, based on the pricing of influenza and shingles vaccines, it is estimated that the price of Abrysvo may range between $60 and $185 per dose (without insurance).

The Global RSV Vaccine Market

Multiple RSV vaccines have received FDA approval or are in advanced stages of clinical trials. In May 2023, the FDA approved GSK’s Arexvy, the world’s first RSV vaccine for adults aged 60 years and older. Clinical trials have shown that Arexvy significantly reduces the risk of developing RSV-associated LRTD by 82.6 percent and severe RSV-associated LRTD by 94.1 percent compared to a placebo.

Moderna also reported positive Phase III results for its RSV vaccine candidate, mRNA-1345. The vaccine demonstrated 83.7 percent efficacy against RSV LRTD in adults aged 60 and older across 22 countries, with no significant safety concerns raised.

AstraZeneca revealed promising Phase III results for its single dose long-acting antibody, nirsevimab, against RSV. Nirsevimab significantly reduced medically-attended lower respiratory tract infections by 74.5 percent and hospitalizations by 62.1 percent in infants and children up to 24 months of age. Nirsevimab has been authorized by the European Union and is currently awaiting FDA approval, with a projected US launch in the third quarter of 2023.

As several vaccines approach their final stage readouts, increased commercialization is expected by 2024. The global RSV vaccine and antibody market is expected to reach $2.56 billion in value by 2024, and grow to $9.53 billion by 2028.