What Is Arexvy, and Why Does It Matter?
Arexvy is a vaccine that helps protect against serious lung illness caused by respiratory syncytial virus (RSV). The FDA has expanded its use to include people 18 to 49 years old who have certain health issues that raise their risk of lower respiratory tract disease (LRTD) caused by RSV. Earlier, this vaccine was approved to prevent RSV-related LRTD in adults 50-59 years old who were at increased risk and anyone 60 or older.
RSV is a common virus that affects the lungs and breathing passages, and it spreads easily from person to person. Young adults with health conditions such as heart or lung disease, kidney disease, obesity, diabetes, or a weakened immune system are at a higher risk of severe RSV-related LRTD and serious complications such as pneumonia, longer hospital stays, and even death. In the United States, RSV causes a significant number of illnesses each year among people 18-49 years old, leading to about 17,000 hospitalizations, 277,000 emergency department visits, and nearly 2 million outpatient visits.
Arexvy contains lab‑made (recombinant) RSV protein (glycoprotein F) that is kept in its most stable form (RSVPreF3 conformation), allowing the vaccine to work with maximum efficacy. As an adjuvanted vaccine, it includes an extra ingredient called an adjuvant, which is added to the vaccine before it is given. This adjuvant helps your immune system respond more strongly to the shot. Arexvy teaches your body's immune system to recognize a key RSV protein so that it can respond faster and more powerfully whenever you get exposed to RSV later.
This approval matters because Arexvy provides at-risk adults who have certain health conditions a new option against RSV, which can cause severe illness, serious complications, expensive treatments, and death.
Why Was It Approved?
This FDA approval is based on results from a phase 3 study that showed that the immune response produced by Arexvy in people 18-49 years old was not inferior to that observed in adults 60 or older.
In the clinical study, a single dose of Arexvy was given to people 18 to 49 years old with predefined stable long-term diseases and a high risk of LRTD, and the outcomes were compared with those of people 60 or older after a month of vaccination. The study's main aim was to see how well the vaccine helped the body fight off both types of RSV (A and B) infection a month after vaccination.
The vaccine had already been shown to work well in an earlier phase 3 trial in which Arexvy lowered the chance of RSV-related LRTD in adults 60 or older, when compared with a placebo. The people in the trial were followed up to the end of the third RSV season (median follow-up time, 30.6 months). The results showed a significant reduction in the risk of RSV-associated LRTD by about 83% during the first RSV season. Vaccine efficacy was 67.2% over two RSV seasons and 62.9% over three RSV seasons. It also cut the risk of severe RSV lung disease by about 94% versus a placebo in that age group.
The safety results were consistent with previous studies used for the first FDA approval. The most common side effects of the vaccine include pain where the shot is given, fatigue, muscle pain, headaches, and joint pain. These usually happened within four days of vaccination.
A post-marketing observational study suggested a higher risk of a rare neurological disorder called Guillain-Barré syndrome during the 42 days after the shot. But the available evidence does not prove that the Arexvy vaccine caused it.
What Do I Need to Know?
Arexvy is given as a single shot into the muscle. Do not get this vaccine if you have ever had a severe allergic reaction to any of its ingredients. Fainting can happen after any shot, so your health care provider may take steps to prevent injury.
Be sure to tell your health care provider about all the vaccinations, medicines, and over-the-counter products, herbal remedies, and vitamin supplements you take, particularly if you are taking medicines that can weaken or suppress your immune system.
Before taking the vaccine, let your health care provider know if you are allergic to Arexvy, or any of its ingredients, or if have a weakened immune system. Also, share other details about your medical history. If your immune system is weakened, your body may not respond as strongly to the vaccine.
Arexvy is not meant for use during pregnancy, as there is no clinical trial data on its safety in pregnant people. In a separate study of a related RSV antigen without the adjuvant, a higher rate of preterm births was seen. This creates uncertainty about using Arexvy during pregnancy. It isn't known if Arexvy passes into breast milk or is safe during breastfeeding, as no studies have looked into its effects on breastfed infants or on milk production. Let your health care provider know if you are pregnant, planning to get pregnant, or breastfeeding before taking Arexvy.
Studies have examined the effects of giving Arexvy at the same time as flu vaccines. Most of the immune responses involving both vaccines were similar to those seen when the shots were given separately. But talk to your health care provider about the best timing and schedule for you if you plan to get both vaccines.
And talk to your health care provider about the potential benefits and risks of this vaccine for you, including your health conditions and other medicines you take.