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CDC recommends new RSV vaccines for older adults

On 21 June 2023, the CDC’s Advisory Committee on Immunization Practices (ACIP) recommended two recently approved vaccines to prevent respiratory syncytial virus (RSV) infections in adults older than 60. I have had RSV vaccines on my personal vaccine wishlist for a while, so it’s good to see these available.

The FDA approved the prefusion F protein-based RSV vaccines, Arexvy (GSK) and ABRYSVO (Pfizer), in May 2023 for use in individuals older than 60.

Let’s take a look at why RSV is a dangerous disease, especially for young children and older adults, and how the two vaccines work.

Respiratory syncytial virus infections

The respiratory syncytial virus is a common, contagious virus that causes infections of the respiratory tract. It is a single-stranded RNA virus, and its name is derived from the large cells known as syncytia that form when infected cells fuse.

It usually causes mild, cold-like symptoms. But it can cause serious lung infections, especially in infants, older adults, and people with serious medical problems. For seniors, RSV infections are dangerous as immune systems weaken.

RSV spreads from person to person through:

  • The air by coughing and sneezing.
  • Direct contact, such as kissing the face of a child who has RSV.
  • Touching an object or surface with the virus on it, then touching your mouth, nose, or eyes before washing your hands.

(I don’t mean to keep repeating myself, but all the measures you take to reduce your risk for COVID-19 seem to be useful for preventing RSV.)

RSV can sometimes lead to pneumonia (infection of the lungs) and congestive heart failure (when the heart can’t pump blood and oxygen to the body’s tissues).

According to the CDC, each year in the United States, RSV leads to approximately—

  • 2.1 million outpatient visits among children younger than 5 years old
  • 58,000 hospitalizations among children younger than 5 years old
  • 177,000 hospitalizations among adults 65 years and older
  • 14,000 deaths among adults 65 years and older

I know these numbers pale next to COVID-19, but before the pandemic, an RSV vaccine was often at the top of the wish list for a new vaccine. And for those people who had children or parents who had to deal with a serious RSV case, they probably wish there was a vaccine too.

Hopefully, these vaccines will soon become available, as new research is quantifying their need:

  • The JAMA Network published an article on 29 December 2021 that suggests RSV poses a greater risk to infants than influenza, while both are associated with substantial mortality among elderly individuals.
  • The journal PNAS published research on 14 March 2022, which found that administering an RSV vaccine to pregnant mothers reduced antimicrobial prescribing among their infants by 12.9% over the first three months.  

The RSV vaccines

Below is information about the two FDA-approved and CDC-recommended RSV vaccines.

Pfizer — The vaccine manufacturer has developed an RSV vaccine, ABRYSVO. Unlike some of the COVID-19 vaccines, this is not an mRNA vaccine. It is a typical vaccine that trains the immune system to recognize the crystal structure of prefusion F-protein, a key form of the viral fusion protein (F) that RSV uses to attach to human cells. There are two forms of the F-protein, and this vaccine targets both. There were phase 3 trials for seniors along with two phase 3 trials for adults. They also have a phase 3 trial that is examining the effectiveness of the vaccines in infants who were born to vaccinated mothers. Some of these trials are still recruiting subjects, so join in if you want.

ABRYSVO showed protection against LRTD infections with three or more symptoms dropped from 89% in season one to 79% by the middle of season two, with protection against LRTD infections with two or more symptoms dipping from 65% to 49%.

GSK — the GSK vaccine, Arexvy, is a single-dose vaccine that contains a recombinant subunit RSV antigen combined with GSK’s proprietary AS01 adjuvant. There are currently four phase 3 clinical trials, some that may still be recruiting subjects — non-pregnant women, pregnant women, pregnant women and infants born to vaccinated women, and booster vaccination after pregnancy.

Arexvy showed efficacy against lower-respiratory tract disease (LRTD) dropping from 83% in season one to 77% by the middle of season two, with protection against severe cases dropping from 94% to 85%, respectively.

Both vaccines seem to show a slight reduction in effectiveness in the second year of the disease, so there might be a need for a booster in subsequent years.

Although the vaccine showed no serious safety signals, there appeared to be a signal for increased risk of Guillain-Barre Syndrome (GBS), a rare disorder where the immune system attacks the peripheral nervous system. GBS often occurs after a viral infection, so we don’t currently know whether the risk of GBS post-vaccination is different than we would observe with RSV itself. Of course, post-marketing surveillance is required of vaccine manufacturers, so if this issue persists, the FDA and CDC will make changes in recommendations. But just to be clear, GBS is an extremely rare condition and there is no information on whether GBS is linked to the vaccine and how it compares to the risk of GBS with an RSV infection.

As I mentioned previously, both vaccines were approved for individuals older than 60, and the ACIP made the recommendation for the same age group. However, there is a small caveat — the vaccine should be given only after discussing it with a healthcare provider, usually to determine if the patient is at risk of RSV.


So science has brought us another vaccine to prevent another dangerous pathogen, the respiratory syncytial virus, which afflicts both the young and old. Research is ongoing for its use in infants and young children, which are more at risk of RSV than any other group.

Michael Simpson
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