Preparing for RSV Season with Vaccinations

Depending on geographic location, it is likely time to prepare for the upcoming respiratory syncytial virus (RSV) season. This common respiratory virus can lead to serious illness, particularly in infants and older adults, but this risk can be reduced by ensuring vaccines reach at-risk populations when they need them. 

RSV leads to upwards of 6.5 million outpatient visits, 350,000 hospitalizations and 23,000 deaths annually in the U.S., according to the Centers for Disease Control and Prevention (CDC). It is the leading cause of hospitalization in infants. An additional 180,000 hospitalizations and 10,000 deaths are also possible in patients over age 50 with underlying health complications such as weakened immune systems.¹ 

RSV can be highly contagious, with signs and symptoms of illness appearing four to six days after infection and contagion lasting three to eight days, or up to eight weeks in the case of immunocompromised patients.1 In mild cases, symptoms of RSV are similar to the common cold, but in severe cases, it can spread to the lower respiratory tract and cause pneumonia or bronchiolitis. Since RSV lowers one’s immunity, infection may also increase the risk of getting COVID-19, and if infections occur together, the severity of COVID-19 is worsened.

Some studies show that an annual RSV vaccine can be 90 percent effective in protecting against infant hospitalizations and 70 percent effective at preventing hospitalizations in older adults.² Yet, despite the scientific success of RSV vaccines, uptake is lower than preferred, and one of the main reasons could be that doctors may not be recommending it.

Creating a culture of immunization prior to the start of each RSV season is the most effective way to increase vaccine coverage rates. This culture includes reminder systems, patient education and open communication regarding the risk-benefit analysis of receiving the vaccine. 

Who Is Most at Risk?

Infants younger than six months old, and premature infants in particular, are most at risk of severe complications from RSV. Estimates suggest most children will have had RSV at least once by age 2 years. In healthy children, symptoms of RSV are usually mild and only require self-care until the patient feels well again. But, it is worth noting that there may be a link between severe RSV during childhood and a chance of developing asthma later in life.

Severe RSV infections pose a risk to adults ages 50 to 74 who have underlying medical conditions such as cardiopulmonary disease and weakened immune systems. Individuals over 75 years old, particularly those living in nursing homes, are at much great risk. In fact, some suspect RSV is likely underdiagnosed in older adults with severe respiratory illnesses, and may be twice as likely in patients with chronic obstructure pulmonary disease (COPD). The risks for this older age group include myocardial infarctions, exacerbation of asthma and COPD symptoms, bronchospasms and pneumonia, particularly for those in nursing homes.¹ 

Seasonality and Geographic Variability

RSV season typically runs from November through March in most of the U.S. with peak season in December and January. However, that season may shorten or lengthen based on seasonality and circulation patterns. For instance, circulation in tropical climates like southern Florida, Hawaii, Puerto Rico and the Virgin Islands differ from those traditionally seen in the mainland U.S. Likewise, circulation patterns in Alaska are less predictable, and the duration of peak virus season is longer than the national average. 

Therefore, the timing of RSV monoclonal antibodies in infants or vaccine administration in pregnant women and older adults is important. Sometimes, public health authorities may broadly elect to revise clinical and public health guidance regarding ideal timing. Similarly, providers must use clinical judgment for individual patients with travel plans to areas of increased RSV activity or when their return occurs outside of the ideal window of infant antibody delivery.³ 

Who Is Vaccine-Eligible?

CDC recommends doctors give monoclonal antibodies to all infants under 8 months if their mother did not receive an RSV vaccine during pregnancy. In most cases, infants born after 14 days of maternal vaccination will not need administration of an RSV antibody. However, in rare circumstances, doctors may administer an RSV antibody to infants whose mothers did receive the RSV vaccine. These circumstances might include certain maternal medical conditions or if infant have undergone cardiopulmonary or other procedures that might have led to a loss of maternal antibodies. The administration of infant monoclonal antibodies should occur between October and March in most of the U.S., or within babies’ first week of life if born between October and March.³ 

Pregnant women may receive a maternal RSV vaccine in the months of September through January when they are between 32 and 36 weeks’ gestation to protect their unborn child against severe RSV complications.³ 

It is sometimes recommended that children aged 8 to 19 months receive an RSV antibody shortly before or as early as possible during their second RSV season. These instances include children who are severely immune compromised, have chronic lung disease, were born prematurely and required medical support at any time during the six months preceding the start of RSV season, have cystic fibrosis and are American Indian or Alaska Native. Additionally, if the mother did not receive the RSV vaccine during pregnancy, if her RSV vaccine status is unknown, or if her baby was born within 14 days of her receiving the RSV vaccine, antibodies may be warranted. It is not advised to give RSV antibodies to children older than 8 months old who are not at increased risk of severe RSV infection. Additionally, RSV antibodies are also not recommended for children 20 months or older.³

CDC recommends adults 60 to 74 years with increased risk for severe RSV and all adults over the age of 75 get an RSV vaccine between September and January.²

Infant RSV Monoclonal Antibodies

One of two methods protects babies against severe RSV infections: Either their mother received a vaccine during pregnancy, or the U.S. Food and Drug Administration (FDA) has approved two monoclonal antibody products for infants. The antibody products, nirsevimab (Beyfortus, approved in 2023) and clesrovimab (ENFLONSIA, approved in 2025), come in prefilled injectable syringes. Both are recommended for infants younger than 8 months when entering their first RSV season.³ 

Once children reach 8 months or they are entering their second RSV season, only nirsevimab has received FDA approval. Nirsevimab may be administered through age 19 months. Clesrovimab does not have FDA approval for administration in children older than 8 months of age or those entering their second RSV season.³ 

It is permissible to administer infant RSV antibodies and routine childhood vaccines in the same visit, with no necessary interval between infant RSV antibodies and live vaccines. However, in accordance with CDC General Best Practices, children who are acutely ill should usually wait to receive an infant RSV antibody.3 

Infant monoclonal antibodies, unlike vaccines, do not activate the immune system. Therefore, they work best in the weeks after being administered and stay effective for around five months during the period when children are most susceptible to a severe infection.

The side effects of RSV monoclonal antibodies are generally mild and include swelling, redness or pain at the injection site that usually resolves quickly. Hypersensitivity reactions are uncommon; however, in February 2024, FDA updated the package insert for nirsevimab to include rare cases of hypersensitivity reactions post-licensure. These findings did not affect a determination of the product’s overall risk-benefit at the October 2024 CDC Advisory Committee on Immunization Practices meeting.⁴ 

Maternal RSV Vaccine

Pfizer’s Abrysvo vaccine protects mothers-to-be against severe RSV when administered between 32 and 36 weeks of gestational age. Approved for use in pregnant women in 2023, Abrysvo is the only RSV vaccine approved and recommended for use by pregnant women. Babies delivered more 14 days from their mother’s RSV vaccination are protected from severe forms of RSV, and they will likely not need further antibody delivery in their first year.⁴ 

It is worth noting that Moderna manufactures a vaccine licensed for adults ages 18 to 59 who are at increased risk of severe RSV. However, Moderna’s vaccine has not been approved for administration in pregnant women.⁴ 

Side effects of Abrysvo in pregnant women include discomfort at the injection site, headache, muscle pain and nausea. While serious adverse events balanced between vaccinated and placebo groups in clinical trials, the vaccine group saw a slight, not statistically significant, rise in preterm births and pre-eclampsia. Because of these potential risks, FDA has only approved Pfizer’s Abrysvo no sooner than 32 weeks. CDC and FDA continue to monitor safety to ensure the benefits of vaccination outweigh risks and will update any safety information accordingly.⁴ 

Adults RSV Vaccines

Three vaccines are FDA-approved to protect adults from severe RSV infections. 

Pfizer’s Abrysvo may be used in adults aged 18 to 59 who are at risk of severe forms of RSV and in older adults over age 60. 

GSK’s Arexvy was approved in 2023 for those aged 50 to 59 who are at an increased risk of RSV and for adults over the age of 60. 

Moderna’s mResvia was approved in 2024 for adults 60 years of age and older. In 2025, FDA also licensed mResvia for adults age 18 to 59 who are at severe risk of RSV infections. Neither Abrysvo, Arexvy nor mResvia has been approved for use in infants or young children, and only Abrysvo is approved for use in pregnant women.⁴ 

Common side effects for each of the RSV vaccines in non-pregnant adults include pain at the administration site, headaches, muscle pain and fatigue. Patients receiving Pfizer’s Abrysvo may also experience nausea.⁴ 

The risk of severe vaccine reactions such as Guillain-Barré syndrome (GBS) increases as one ages. At an October 2024 Advisory Committee on Immunization Practices meeting, FDA presented updated post-licensure safety monitoring data for GSK and Pfizer vaccines focusing on confirmed GBS cases. Moderna’s vaccine, with less time on the market, does not yet have post-licensure safety data available. 

The data showed a small number of patients 60 years and older who received GSK’s Arexvy and Pfizer’s Abrysvo vaccines developed serious neurological conditions such as GBS (the results were statistically significant for the GSK vaccine but not statistically significant for the Pfizer vaccine), and FDA estimated the risk of GBS to be on the order of 10 excess cases per one million vaccinated adults 60 or older. Ongoing monitoring of all vaccines continues, and any necessary safety data will be udpated accordingly.⁴ 

The Pink Book: Immunization Strategies for Healthcare Practices and Providers

CDC recommends healthcare providers develop an immunization quality improvement plan that increases vaccine uptake per guidelines laid out in The National Vaccine Advisory Committee Standards for child and adolescent immunization practices. These quality improvement programs are an excellent way to measure outcomes in improving vaccine coverage and to reduce disparities.

Appointing an immunization coordinator to act as the point person for all things immunization is an effective way to cross-coordinate the immunization needs of patients and the clinic, including proper storage and handling of the products themselves. 

Daily reminder lists housed in electronic health records can be set up for each patient who will be seen in the clinic and who is vaccine-eligible. These lists will not only notify medical personnel at each encounter when a vaccine is due or past due, but they enable open and honest conversations so patients can freely ask questions and discuss concerns. 

Clinics may also elect to initiate standing orders so that non-physician medical personnel who are trained to deliver vaccines correctly may do so. That training includes screening for contraindications and monitoring for post-vaccination adverse events. If patients agree to be vaccinated, physicians should consider giving the vaccine in the same office visit, then record the shot in the state’s Immunization Information Systems database so an accurate and up-to-date record is available for all the patients’ providers.

Participation in the Vaccines for Children (VFC) program reduces the financial burden of vaccine administration for low-income patients. It also reduces upfront costs, since vaccines delivered under the VFC program are not charged to the clinic. 

Achieving Vaccination Goals

Effective two-way patient communication is the clearest, best path to achieving vaccination goals. Medical personnel should be ready to discuss tailored reasons the RSV vaccine might be right for patients, and address patient questions and concerns. Medical personnel must document patients’ decisions should they not wish to be vaccinated, and the reason for which may be optionally recorded in their records. 

Even if patients decline, decisions may change over time along with their medical needs. Each appointment is an opportunity to educate and inform so patients understand the importance of vaccines. 

RSV season is nearly here. Will your patients be ready?