Daily Mosnodenvir as Dengue Prophylaxis in a Controlled Human Infection Model
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RSV Vaccine Breakthrough: Protecting Infants and Older Adults
Understanding the RSV Threat
Respiratory Syncytial Virus (RSV) is a ubiquitous respiratory virus that typically causes mild, cold-like symptoms.However, for infants, young children, and older adults, RSV can led to serious complications like bronchiolitis and pneumonia. Before the advent of these vaccines, RSV was responsible for an estimated 60,000-160,000 hospitalizations and 6,000-10,000 deaths annually among older adults in the united States. Infants faced a similar burden, with a significant proportion requiring hospitalization.
The virus spreads through respiratory droplets produced when an infected person coughs or sneezes. Symptoms usually appear within 4 to 6 days of infection and include a runny nose, decreased appetite, cough, sneezing, fever, and wheezing. While most people recover within a week or two, severe cases can necessitate hospitalization and supportive care.
The New Vaccines: A Two-Pronged Approach
In May 2023, the Food and Drug Administration (FDA) approved two groundbreaking RSV vaccines: Arexvy, developed by GSK, and abrysvo, created by Pfizer. These vaccines represent a major advancement in preventative medicine, offering targeted protection to different at-risk groups.
Arexvy (GSK)
Arexvy is a recombinant subunit vaccine specifically designed for adults aged 60 years and older. It utilizes a stabilized prefusion F protein, a key component of the RSV virus, to elicit an immune response.Clinical trials demonstrated approximately 82.6% efficacy in preventing RSV-associated LRTD with a symptom score of ≥3. The vaccine’s efficacy was observed across various RSV subtypes and in individuals with underlying medical conditions.
Abrysvo (Pfizer)
Abrysvo is a bivalent RSV vaccine offering dual protection. It’s approved for both older adults (60 years and older) and for the prevention of RSV in infants through maternal immunization. Pregnant individuals recieve a single dose of Abrysvo between 32 and 36 weeks of gestation, which stimulates the production of antibodies that are then passed on to the baby, providing protection during the first six months of life. Clinical trials showed approximately 70% efficacy in preventing severe LRTD in infants born to vaccinated mothers. For older adults,Abrysvo demonstrated around 66.3% efficacy against RSV-associated LRTD.
Clinical Trial Data: A Deeper Dive
The efficacy data published in the New England Journal of Medicine (November 27, 2025, Volume 393, Issue 21, pages 2107-2118) provides a detailed look at the clinical performance of these vaccines. The trials involved tens of thousands of participants across multiple sites. Key findings include:
| Vaccine | Target Population | Efficacy Against RSV-Associated LRTD | Serious Adverse Events |
|---|---|---|---|
| Arexvy (GSK) | Adults ≥60 years | 82.6% | Rare; primarily injection-site pain and fatigue |