Respiratory Syncytial Virus (RSV) Vaccine Safety

Overview

Respiratory Syncytial Virus, or RSV, is a common respiratory virus that usually causes mild, cold-like symptoms. Most people recover in a week or two, but RSV can cause severe illness, particularly in infants and older adults. You can protect against severe RSV with immunization. CDC, working with FDA and other federal agencies, monitors RSV immunizations using several safety systems.

Available immunizations

For older adults

FDA has approved three vaccines to protect older adults against severe lower respiratory tract disease (LRTD) caused by RSV.

• Pfizer's RSV vaccine (Abrysvo) was approved in 2023. Pfizer RSV vaccine is approved for people ages 60 years and older and people ages 18 to 59 years who are at increased risk of RSV disease to prevent LRTD caused by RSV.
• GSK's RSV vaccine (Arexvy) was approved in 2023. GSK RSV vaccine is approved for people ages 60 years and older and people ages 50 to 59 years who are at increased risk of RSV disease to prevent LRTD caused by RSV.
• Moderna's RSV vaccine (mResvia) was approved in 2024. Moderna RSV vaccine is approved for people ages 60 years and older to prevent LRTD caused by RSV.

CDC recommends that all people ages 75 years and older and people ages 60 to 74 years who are at increased risk for severe RSV disease receive a single dose of RSV vaccine.1

For infants and certain young children

• FDA approved nirsevimab (Beyfortus) in 2023. Nirsevimab is an injectable monoclonal antibody for the prevention of LRTD caused by RSV.
• Nirsevimab is approved for infants born or entering their first RSV season and for some young children who are at increased risk for severe RSV disease and entering their second RSV season.

For pregnant people (maternal RSV vaccine)

• FDA approved Pfizer RSV vaccine (Abrysvo) in 2023. Pfizer RSV vaccine is approved for pregnant people at 32 through 36 weeks gestational age to protect their babies from LRTD caused by RSV.

• Pfizer is the only RSV vaccine approved and recommended for use in pregnant people. GSK (Arexvy) and Moderna (mResvia) RSV vaccines are not recommended for pregnant people.

Who should & should not get these immunizations

Specific RSV immunization recommendations vary by group. See information for:

• Older adults (60 years and older)
• Pregnant people, infants, and certain young children

Common side effects

Vaccines and monoclonal antibody products, like any medical product, can have side effects. Most common side effects reported after RSV immunization are usually mild or moderate.

Pfizer (Abrysvo)

For older adults

• Pain where the shot is given
• Fatigue (feeling tired)
• Headache
• Muscle pain
• Nausea

For pregnant people

• Pain where the shot is given
• Headache
• Muscle pain
• Nausea

GSK (Arexvy)

• Pain where the shot is given
• Fatigue (feeling tired)
• Headache
• Muscle and joint pain

Moderna (mResvia)

• Pain where the shot is given
• Fatigue (feeling tired)
• Headache
• Muscle and joint pain
  

Nirsevimab (Beyfortus)

• Pain, redness, hardness, or swelling where shot is given
• Rash

How CDC monitors vaccine safety

CDC and FDA are committed to monitoring the safety of vaccines. Once vaccines are licensed or authorized by FDA for use in the United States, CDC, FDA, and other federal agencies work together to monitor them using several safety systems.

Adverse Events After Nirsevimab Administration: Adverse events following receipt of nirsevimab, during which no other immunizations were received, may be reported to MedWatch online (https://www.fda.gov/medwatch) or by calling FDA at 1-800-332-1088.

Share how you feel after RSV vaccination with V-safe

V-safe is part of the U.S. vaccine safety system that monitors the safety of vaccines. V-safe lets you share with CDC how you or your dependent feel after getting an RSV vaccine. After you sign up and select the vaccine you received, V-safe will send you questions by text message or email to ask how you feel after vaccination. It's important to know that sharing how you feel, even if you don't experience vaccine side effects, helps CDC monitor the safety of select vaccines.

A closer look at the safety data

For older adults

Clinical trial safety data

In clinical trials assessing the safety of RSV vaccines in adults ages 60 years and older, the frequency of serious adverse events (SAEs) was similar in the vaccinated group compared to the placebo (control, or unvaccinated) group.

Among adults ages 60 years and older receiving GSK (Arexvy) and Pfizer (Abrysvo) RSV vaccines, a small number of people developed serious neurologic conditions (conditions related to the brain, spinal cord and nerves throughout the body), such as Guillain-Barré syndrome (GBS), within 42 days after vaccination. Given the small number, it was unclear if the vaccines caused these events or if they occurred due to chance.

In clinical trials among adults ages 60 years and older receiving the Moderna RSV vaccine (mResvia), there were no reported cases of GBS within 42 days after vaccination.5

Post-licensure safety data

During the October 2024 Advisory Committee on Immunization Practices (ACIP) meeting, FDA presented updated post-licensure safety monitoring data on GSK and Pfizer RSV vaccines from a partnership between FDA and the Centers for Medicare and Medicaid Services.

Data included a large study population and focused on confirmed GBS cases identified in medical claims data and verified following medical record review. Results suggested an increased risk of GBS after RSV vaccination with both GSK and Pfizer RSV vaccines. Results showed that the GSK RSV vaccine had a statistically significant association with GBS, while the Pfizer RSV vaccine had a similar, but not statistically significant, association. In the analysis, fewer doses of Pfizer RSV vaccine were administered compared to GSK RSV vaccine. For both vaccines, FDA estimated the risk of GBS to be on the order of 10 excess cases per 1 million vaccinated adults 60 or older6.

These findings have limitations. Many factors may affect the results, including potential misclassification of GBS cases in the analysis. Additional analyses on the risk of GBS after RSV vaccination are underway, and findings will be shared as data become available16.

FDA licensed the Moderna RSV vaccine (mResvia) in May 2024. Because of its recent introduction, post-licensure safety data are not yet available for this vaccine, which is currently being monitored in V-safe and VAERS.

CDC and FDA continue to monitor and communicate about the safety of older adult RSV vaccination to ensure the benefits of vaccination outweigh possible risks, including GBS.

For infants and young children

Clinical trial safety data

No safety concerns were observed during the clinical trials for infants and young children who received the nirsevimab passive immunization. The occurrence of SAEs was not elevated in infants receiving nirsevimab compared with those receiving placebo.3

Post-licensure safety data

In February 2024, FDA updated the nirsevimab package insert to share that cases of serious hypersensitivity reactions (e.g., hives, fast breathing) have been reported post-licensure.

As of the October 2024 ACIP meeting, no new safety information that would affect the overall benefit or risk of nirsevimab has been identified.

For pregnant people

Clinical trial safety data

In clinical trials assessing the safety of Pfizer RSV vaccine (Abrysvo) in pregnant people at 24 through 36 weeks' gestation, SAEs in pregnant people and infants were balanced between the vaccinated and placebo groups.

Clinical trials identified an increase in the number of preterm births (births occurring before the infant has fully developed in the mother's womb) among pregnant people who received the vaccine. Though this was not a statistically significant increase, FDA approved Pfizer RSV vaccine for pregnant people at 32 to 36 weeks' gestation to avoid the potential risk for preterm birth at less than 32 weeks' gestation.

A non-statistically significant increase in hypertensive disorders of pregnancy was also observed during 24 through 36 weeks' gestation. It is not clear if this is a true safety problem related to RSV vaccination or if this occurred for reasons unrelated to vaccination.2

Post-licensure safety data

Post-licensure safety data from VAERS, V-safe, and the Vaccine Safety Datalink (VSD) for the first season of use of Pfizer RSV vaccine for pregnant people are consistent with clinical trial safety data.

Preliminary findings from a VSD study for the first season of use of Pfizer RSV vaccine for pregnant people found that RSV vaccination during 32 through 36 weeks’ gestation was not associated with an increased risk of preterm birth or babies being born small for their gestational age (SGA).9

Additional studies are being conducted to look more closely at the potential risk for high blood pressure issues in mothers, including pre-eclampsia, and preterm birth. 2479

CDC and FDA continue to monitor and communicate about the safety of maternal RSV vaccination to ensure the benefits of vaccination outweigh possible risks.

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