Updates with Respiratory Syncytial Virus (RSV)

Since the recording of this episode, the RSV vaccine has officially been approved by the CDC and should be available starting this month!

What is RSV?

Negative sense, single-stranded RNA virus
Name is derived from the large cells known as syncytia that form when infected cells fuse

Usually causes mild, cold-like symptoms in healthy individuals, and most people will recover in 1-2 weeks
Most of the time, symptoms are localized to upper respiratory tract, but can also cause lower respiratory tract infections
However, infants and older adults are more likely to develop severe disease that require hospitalization
Most children under the age of 2 will contract RSV due to contact with others

Most common cause of bronchiolitis and pneumonia in children <1 year
Leads to 2.1 million outpatient visits as well as 58,000 - 80,000 hospitalizations per year
Also leads to 100-300 deaths among children <5 annually

Why are we discussing RSV now?

Because patients are going to start asking you about it due to two recent developments!
RSV Vaccine

Recently, FDA approved the Abrysvo vaccine for RSV use in infants up to 6 months of age and older adults (July 2023)
Even more recently (8/21/2023), the FDA approved the RSV vaccine for pregnant individuals to prevent RSV in infants

Approved for use between 32-36 weeks gestation
Antibodies can cross the placenta and protect the infant for up to 6 months of age
However, the CDC has not yet set recommendations about Abrysvo, and will not do so until October 2023

This is a bivalent vaccine composed of two recombinant RSV fusion surface glycoproteins to protect against RSV A and B strains
The Data - two randomized controlled trials

Pregnant patients - 3682 patients weeks 24-36 weeks were given the vaccine and 3697 received placebo

There were significantly fewer medically attended severe lower respiratory tract illnesses in infants within 90 days after birth in those that received the vaccine (efficacy 81.8%, 99.5% CI 40.6- 96.3)
There were also fewer medically attended severe lower respiratory tract illnesses within 180 days after birth (efficacy 69.4%, 97.58% CI 44.3-84.1%)
Similar adverse events in both groups

However, in safety studies, low birth weight and jaundice in infants occurred in higher rate in the vaccine group
There is also an imbalance of preterm births in abrysvo recipients (5.7%) vs. placebo (4.7%), but data is currently insufficient to establish a causal relationship with the vaccine
This is why current recommendation is to give after 32 weeks of gestation

Older adults - >18,000 adults 60 years or older were given vaccine, and another >18,000 similar cohort were given placebo

Significantly fewer RSV-associated lower respiratory tract illnesses with two signs or symptoms in the vaccine group compared to placebo group (efficacy 66.7%, 96.7% CI 28-85.8)
Significantly fewer RSV-associated lower respiratory tract illness with 3 signs or symptoms in vaccine group (efficacy 85.7%, 96.7% CI 32-98.7)
Higher rates of local reaction with vaccine (12% vs. 7%), and similar rates of adverse events through 1 month after injection

Currently, FDA is requiring the company to conduct postmarketing studies to assess risk of preterm birth and pre-eclampsia

FDA has approved the use of nirsevimab (trade name Beyfortus, a long-acting monoclonal antibody) for use to prevent lower respiratory tract disease due to RSV in infants and young children on 7/17/2023
Recommendation

All neonates and infants born during or entering their first RSV season at <8 months of age may receive this antibody for prevention
Also children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season

In one trial of preterm infants born at 29-35 weeks gestation, 969 received single dose of nirsevimab, and 484 received placebo

Those who received nirsevimab, 2.6% experienced medically attended RSV LRTI, compared to 9.5% of infants who received placebo (reduces risk by 70%)

Another trial of infants born at >35 weeks gestation, 994 received nirsevimab, and 496 received placebo

Antibody group had 1.2% MA RSV LRTI compared to 5.0% of infants who received placebo (reduces risk by 75%)

Final trial was a randomized, double-blind, active-controlled multicenter trial to prove safety

Beyfortus vs. palivizumab (monoclonal antibody used previously to decrease severe disease caused by RSV; only used in those children at high risk for RSV, including premature infants <35 weeks gestation who are also <6 months of age, children <2 who require treatment for bronchopulmonary dysplasia, and children <2 who have hemodynamically significant congenital heart disease)
925 preterm infants and infants with chronic lung disease of prematurity or congenital heart disease → Beyfortus was non-inferior in terms of safety

Some lingering questions

The monoclonal antibody should be available this fall, per FDA
Vaccines should be available at doctor’s offices and at pharmacies if CDC approves in October
Monoclonal antibody should be available at pediatrician’s offices and in hospitals after delivery

Per the American Academy of Pediatrics, one dose of Beyfortus is $495 for both the 50 mg and 100 mg doses
Per Pfizer, the RSV vaccine Abrysvo will cost somewhere between $180-$270
For reference, the pediatric influenza vaccines cost somewhere between $14 - $30

Weekly Notes