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  • Writer's pictureDr. Bow Tie

RSV: Potentially Deadly - But Now a New Vaccines and a Monoclonal Antibody!

Updated: Nov 13, 2023

It’s that time of year! Fall is in full swing in the northern hemisphere and that means apple picking, hay rides, and gathering at holidays, but also means being indoors more and more likely to get and spread respiratory viruses, specifically COVID, influenza, and RSV. I have talked at length about COVID and the flu annually, but there are updates on the RSV front. We have vaccines!

I have written about RSV before - here’s part of my summary from a year ago:

“RSV has been around for quite a while (since the 1950s!). If you have had young children in the last ten years, you are likely aware of RSV. It is actually a problem in older adults as well, and it is one of three viruses you will likely be tested for if you go to the emergency department with upper respiratory symptoms (the other two being SARS-CoV-2 and influenza). RSV is usually seasonal, similar to influenza and rhinovirus (the common cold), and like those viruses and COVID-19, it can cause a range of illness from mild cold-like symptoms to a severe lands-you-in-the-hospital-on-oxygen infection. Repeat infections are possible, though first-time infections (especially in babies) are usually the hardest.”

We saw a decrease in RSV in 2020-2021 because masking and other mitigation measures worked well against it, similar to influenza. As those measures have stopped, we are seeing an increase in RSV. The populations most vulnerable are infants and the elderly, along with anyone with a compromised immune system. However, infections can be rough on anyone.

Until this year, all we could utilize was non-medical preventative measurements and then if someone got infected, they would have to get treated with supportive medications ranging from steroids to nebulized breathing treatments and oxygen. This year we can introduce new preventative methods: two vaccines for those over age 60, a vaccine for pregnant folks, and a monoclonal antibody for infants. This is great news!


There are two new RSV vaccines, Abrysvo (Pfizer) and Arexvy (Glaxo-Smith-Kline). Both are protein-subunit vaccines (not mRNA), targeting the fusion glycoprotein (F) of RSV. Both were approved in May 2023 (full approval by the FDA, not emergency use authorization). Both underwent randomized, placebo-controlled trials that showed great results in preventing lower-respiratory tract disease from RSV (the infection that lands most babies and adults in the hospital).

Arexvy (in a trial of 25,000 participants) showed an 82.6% efficacy of preventing RSV-confirmed lower respiratory tract disease (in general, in the first RSV season after vaccination) and 94.1% efficacy against severe RSV-associated disease (severe enough to prevent daily activities).

Abrysvo (in a trial of >37,000 participants) showed an 88.9% efficacy of preventing RSV-confirmed lower respiratory tract disease (in general, in the first RSV season after vaccination, with ongoing analysis to measure efficacy in the 2nd RSV season after vaccination) and 81.0% efficacy against RSV-associated disease requiring medical attention (hospitalization).

Both were well-tolerated with mild side effects, and approved for individuals 60 and older.

Abrysvo is also approved for those pregnant between 32-36 weeks, in order that they develop and pass on maternal antibodies against RSV. As the trial went into Phase III for its adult testing, they also did a Phase III trial for pregnant people and their newborns (which is not usually done and leaves people wondering what to do with their pregnant patients, so this is huge!). Arexvy is NOT approved for pregnant folks (the trial was stopped early due to a higher number of preterm births, but this was NOT seen with Abrysvo).

Both vaccines can be taken with other vaccines, such as COVID-19 or influenza. There are still no signs of increased adverse events of pregnancy with any of the COVID-19 or influenza vaccines.


There is a new monoclonal antibody, nirsevimab-alip (Beyfortus). If you get Abrysvo at least two weeks prior to giving birth, baby should not need Beyfortus if immunocompetent. If you’re deemed out of the window, OR if you end up delivering within 2 weeks (may not be enough time to create antibodies) then yes, baby can get Beyfortus.

Generally speaking, side effects seem to be mild, just rash and injection site reactions in both adults and babies, respectively. Risk seems to be low.

Some of you will say that RSV is just a cold or that there are too many vaccines. But some of you know someone whose child ended up severely ill due to RSV. New vaccines and medications to prevent/treat these diseases (that are proven to work) are how we improve healthcare.

As always, I welcome your questions.


Edward Nirenberg's much more in-depth article on RSV (from a year ago), including history, biochemistry, pathophysiology, and treatments and vaccine developments:

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