New vaccines offer hope in the fight against RSV

August 8, 2023

Halle Sinnott

Although it doesn't usually get as much attention as influenza, RSV (respiratory syncytial virus) poses a big health risk to infants and older adults. According to the Centers for Disease Control and Prevention, the disease results in 58,000 to 80,000 children under 5 going to the hospital each year, along with 60,000 to 160,000 older adults. Those numbers spiked in 2022 as people emerged from COVID-19 isolation without much natural immunity.^1,2,3

While anyone can get RSV, the virus can cause serious lower respiratory tract disease (LRTD) in the very young, whose airways can easily become clogged, and the very old, who have weakened immune systems. Those with severe symptoms often need mechanical ventilation and/or IV fluids while they fight off the infection.⁴

Help is on the horizon through new vaccines. In this article, we'll look at how effective the new vaccines are and when they're likely to become available.

RSV Vaccines for Older Adults

In May 2023, the U.S. Food and Drug Administration approved two RSV vaccines for adults who are at least 60 years old. They are GSK's AREXVY® and Pfizer's ABRYSVO™. Here's what you need to know about these vaccines.^5,6

How are the vaccines administered?

The vaccines are injected into the muscles of the upper arm, much like influenza and COVID-19 vaccines.

How were the vaccines tested?

For AREXVY, researchers conducted a randomized clinical trial with about 25,000 older adults in the US and overseas. About half received a single dose of AREXVY, and about half received a placebo. For Abrysvo, researchers conducted a similar trial with about 34,000 individuals.^5,6

How effective are the RSV vaccines?

AREXVY reduced the risk of RSV-associated LRTD by 82.6%, while the risk of RSV-associated LRTD dropped by 94.1%. Abrysvo cut the risk of RSV-associated LRTD with two or more symptoms by 66.7% and the risk of RSV-associated LRTD with three or more symptoms by 85.7%.^5,6

What risks are associated with AREXVY and Abrysvo?

In clinical trials, some participants reported symptoms that are common with many vaccines, including localized pain, fatigue, muscle pain, headache and joint pain.^7,8

How long does protection last?

That's an open question. The manufacturers are working to establish how effective the vaccines are across multiple seasons and whether revaccination is needed. For example, research has shown that AREXVY is effective over two seasons.⁹

When can I get vaccinated?

AREXVY and Abrysvo should be available for protection before the upcoming RSV season. In June 2023, the CDC's Advisory Committee on Immunization Practices (ACIP) recommended the vaccines for adults ages 65, as well as for adults ages 60 to 64 using "shared clinical decision-making," in the words of the ACIP. The director of the CDC still needs to formally endorse the vaccines.^₅

A Potential RSV Vaccine for Pregnant Women

Abrysvo may also soon be approved to protect infants. Although that process is a few months behind the adult approval process, here's what you need to know.

How is the vaccine administered?

The vaccine is given to expectant mothers between 24 and 36 weeks of pregnancy. As with older adults, it's injected into the muscles of the upper arm.¹⁰ The antibodies it triggers are passed on to the fetus, giving a newborn protection at birth.

How was the vaccine tested?

Researchers tested Abrysvo on about 7,300 women who were at least 24 weeks into their pregnancies. As with the adult study, half received the vaccine and half received a palcebo.¹⁰

How effective is the vaccine?

During the first three months after birth, the vaccine was 82% effective at preventing severe infections and 57% effective at keeping babies from needing medical attention for RSV. At six months of age, those numbers were 69% and 51%, respectively.¹⁰

What risks are associated with giving Abrysvo to pregnant women?

Preterm births were slightly higher among trial participants who received Abrysvo (5.7% vs. 4.7% who received the placebo). The difference wasn't statistically significant, but Pfizer plans to continue studying the vaccine's safety.¹⁰

Another Option for Infants: Beyfortus®

In July the FDA panel approved an injectable antibody drug for infants called Beyfortus (nirsevimab), which was developed by Sanofi and AstraZeneca. It joins Synagis® (palivizumab), an antibody injection that's already available. Although not a full-fledged vaccine, Beyfortus has been shown to reduce the risk of severe RSV infections. It can be given to newborns and infants born during or entering their first RSV season, as well as to children up to 24 months of age who remain vulnerable to severe RSV disease during their second RSV season.^11,12

Beyfortus is injected into the thigh muscle before RSV season starts or at birth. In clinical trials involving about 3,000 babies, the drug lowered the risk that a baby would need medical attention for RSV by 70% to 75% and the risk of hospitalization for RSV by 60% to 80%. Side effects like fever and rash were rare and mild, and protection lasted for five months or longer.¹³