Adult RSV Vaccines: Q&A With the CDC's Dr Michael Melgar

Earlier this year, the US Food and Drug Administration (FDA) approved the first respiratory syncytial virus (RSV) vaccines in the United States for older adults. Adults aged 60 years or older may get an RSV vaccine after discussion with their healthcare provider according to recommendations from a Centers for Disease Control and Prevention (CDC) advisory committee. Medscape Medical News spoke with Michael Melgar, MD, with the CDC's National Center for Immunization and Respiratory Diseases, about what these recommendations mean, who may benefit from RSV vaccine, and when these vaccines will become available.

What do doctors need to know about RSV and its symptoms?

RSV is a common respiratory viral illness that generally causes mild cold-like symptoms. Most people recover in 1 or 2 week. However, RSV can be serious, especially for infants and older adults. Although it's a common cause of pneumonia and respiratory disease in adults, RSV is often underrecognized in this age group.

It's important to note that RSV can be difficult to differentiate from COVID-19 or from influenza in adults just on the basis of symptoms. Infection with RSV can also trigger worsening of some medical conditions that are common in adults, like asthma, congestive heart failure, and chronic obstructive pulmonary disease (COPD). To give an idea of how much this affects older adults, it's estimated that between 60,000 and 160,000 older adults in the United States are hospitalized. Every year, 6000 to 10,000 older adults die from RSV infection.

What are the differences between the RSV vaccines?

There are two RSV vaccines that are now approved and recommended for adults aged 60 years or older to prevent RSV. Their trade names are Arexvy, manufactured by GlaxoSmithKline, and Abrysvo, manufactured by Pfizer. These are the first RSV vaccines licensed in the United States, and they will help protect older adults when multiple respiratory viruses circulate during the upcoming fall and winter season. The GlaxoSmithKline and Pfizer vaccines are both protein-based subunit vaccines, which means that they consist of a subpart of the RSV virus that causes the immune system to produce antibodies against RSV. Both are approved as a single dose currently, and both were shown to protect against symptomatic lower respiratory tract disease caused by RSV in adults aged 60 years or older, with efficacy estimated to be greater than 80% for the first season after vaccination. One difference between the vaccines is that GlaxoSmithKline's vaccine includes an adjuvant, which is a component that's intended to enhance or boost the immune response when the vaccine is given, whereas Pfizer's vaccine doesn't contain an adjuvant.

What is the vaccine recommendation?

The CDC's Advisory Committee on Immunization Practices (ACIP) recommendations for use of the new RSV vaccines are described in a July 21 Morbidity and Mortality Weekly Report (MMWR) report. CDC recommends that adults aged 60 years or older may receive a single dose of RSV vaccine using shared clinical decision-making. In short, this means that adults aged 60 years or older should talk to their healthcare provider about whether RSV vaccination is appropriate for them. The decision on whether to administer this vaccine could be informed by the patient's health status, their risk for severe RSV disease (as determined by their healthcare provider), and other patient-specific factors.

How is this different than a routine aged-based recommendation?

Under an aged-based recommendation, everybody who is a certain age or older or whose age is within a specified age window is by default recommended to get a vaccine. Of course, there are situations where there may be patient-specific reasons not to get a vaccine, but the default is that everybody in that age group is recommended to get the vaccine. In shared clinical decision-making, there is no default. Rather, it means that, in this case, patients aged 60 years or older and their clinicians should discuss RSV and RSV vaccination and determine whether the patient may be more vulnerable to RSV infection. Patients who are at higher risk include people with chronic cardiovascular diseases like congestive heart failure and coronary artery disease; chronic lung diseases like COPD and asthma; endocrine diseases like diabetes; neurologic conditions; as well as kidney, liver, or hematologic conditions.

Adults aged 60 years or older who have a weakened immune system are known to be at higher risk for severe RSV and death from RSV, and these patients could potentially benefit from vaccination. One caveat is that RSV vaccination to date has not been studied in immunocompromised people, so how well the vaccine works in those individuals is unknown. But again, because they are at such high risk, these patients would benefit from that discussion with their healthcare provider.

What are the expected benefits of the RSV vaccine?

Vaccination with a single dose of RSV vaccine in clinical trials demonstrated moderate or high efficacy in preventing symptomatic RSV associated lower respiratory tract disease. The effect was shown for two consecutive RSV seasons after that single dose in older adults. The efficacy seen from the trials against symptomatic illness might also indicate efficacy against more severe outcomes like hospitalization and death; overall, RSV vaccination has the potential to prevent substantial burden of disease among vulnerable older adults.

Are there any known risks of taking this vaccine?

The review of the existing data by FDA and by the CDC for these two licensed RSV vaccines indicates that they are safe and effective. Minor adverse events that happen with any vaccine include pain at the injection site, fever, swelling or redness at the injection site, and fatigue. Patients who have experienced some of those symptoms with any other vaccine might be more likely to experience those same symptoms after RSV vaccination.

We do want to note that in the clinical trials, a very small number of participants developed Guillain-Barré Syndrome (GBS) or other inflammatory neurologic conditions similar to GBS after being vaccinated with the RSV vaccine. The significance of these cases is unclear. Because there were so few of these cases, there isn't enough information to determine whether the risk after vaccination is elevated or these handful of cases occurred simply due to chance. CDC and ACIP use the safety monitoring systems in place to inform vaccine recommendations and will continue to monitor and review data to ensure the safety of RSV vaccines along with all other vaccines and keep the public informed of findings, as has been done in the past. The FDA has also required that the two manufacturers, GlaxoSmithKline and Pfizer, conduct post-marketing safety studies to evaluate risk for GBS or other neurologic adverse events.

As for all vaccines, CDC asks that patients, caregivers, and vaccine providers report any adverse events after RSV vaccination to the Vaccine Adverse Event Reporting System, which is managed by the CDC and FDA. They should report any adverse event even if it is not clear whether the vaccine was the cause.

Can an RSV vaccine be administered with other vaccines?

The RSV vaccine can be given at the same visit with other vaccines for adults. That includes the flu vaccine and COVID-19 vaccine, which will also provide protection against respiratory viruses this fall. Receiving multiple vaccines on the same day provides a better opportunity for older adults to get up-to-date with important recommended vaccines because it requires fewer appointments. However, the common side effects of vaccination, like fever and soreness at the injection site, might be increased when the RSV vaccine is given with other vaccines like the flu vaccine. Some studies suggest that it's also possible that RSV and flu vaccines may not produce quite as strong of an immune reaction if they're given on the same day, but the clinical significance of that small difference is also not clear. Currently, there aren't other study results available on administering the RSV vaccine at the same visit as the COVID-19 vaccine or other adult vaccines, but research is ongoing.

When deciding whether to recommend another vaccine at the same visit for an RSV vaccine, clinicians should consider whether a patient is behind or is at risk of becoming behind on other recommended vaccines, a patient's risk for relevant vaccine-preventable diseases, and how likely it would be for each vaccine to cause these mild common side effects.

When will these vaccines be available?

We expect RSV vaccines to be available in some locations by the end of July, and distribution and availability will increase over the coming months. The CDC recommends that eligible older adults, after discussion with their healthcare provider, be vaccinated against RSV as soon as the vaccine is available rather than waiting for the late summer or early fall.

Do the vaccines need any special or unusual handling instructions?

The storage and handling requirements for the two RSV vaccines are similar. Both consist of lyophilized powder and liquid components and require reconstitution before use. Both vaccines also require refrigeration for storage at 2-8 ºC (35.6-46.4 ºF) with protection from light. Both should be administered within 4 hours after reconstitution.