CDC’s MMWR Early Data Suggest RSV Vaccination Benefits Outweigh Risks in Senior Population

The federal agency’s report still recommended vaccination for those aged 60 years and older.

Image credit: CDC

The latest CDC Morbidity and Mortality Weekly Report (MMWR) has suggested that, despite some lingering concerns about the incidence of Guillain-Barré syndrome (GBS) as a possible safety concern, vaccination against respiratory syncytial virus (RSV) lower respiratory tract disease is still recommended in adults aged 60 years and older.¹

This news comes in a timely fashion, as a number of RSV vaccines have either entered the market or expanded their indications to include this patient population since 2023—namely, GSK’s adjuvanted vaccine Arexvy (RSVPreF3 +AS01E), which was approved for older adults in May 2023²; Pfizer’s bivalent prefusion F vaccine Abrysvo, which was greenlit in June 2023³; and most recently, Moderna’s mRNA 1345 vaccine, mRESVIA, which was approved in May 2024.⁴ Notably, this MMWR only included monitoring for the former 2 vaccines.

The incidence of GBS in the clinical trials of GSK’s Arexvy and Pfizer’s Abrysvo vaccines compelled the CDC and FDA to monitor these occurrences in the past year through the Vaccine Adverse Event Reporting System (VAERS) and V-safe, an active U.S. surveillance system that sends web surveys to enrolled participants during the 6 weeks after vaccination. Those occurrences of GBS were ultimately shown to be consistent with the trials, but higher than estimated expected background rates in a vaccinated population. The rates per million doses were 5.0 and 1.5 for Abrysvo and Arexvy, respectively.

The MMWR authors, including Anne M. Hause, PhD, of the Division of Healthcare Quality Promotion within the National Center for Emerging and Zoonotic Infectious Diseases at the CDC, noted that earlier this year, “[the Advisory Committee on Immunization Practices] announced that, based on a thorough review of currently available data, the estimated benefits of RSV vaccination continued to outweigh potential risks. RSV vaccination continues to be recommended for adults aged ≥60 years using shared clinical decision-making.” Hause et al added that the FDA and CDC are continuing to conduct evaluations of adverse events of special interest, with the hopes that the “results of these studies will help guide future CDC RSV vaccine recommendations.”

The report included data from May 3, 2023, to April 14, 2024, including patients aged 60 years and older who received at least 1 dose of a recommended RSV vaccine. From August 4, 2023, to March 30, 2024, at least 10.6 million individuals in this age group received an RSV vaccine. Of that larger cohort, an estimated 7.2 million adults aged 60 years and older received the GSK RSV vaccine, and 3.4 million received the Pfizer RSV vaccine.

For all safety data the rates and incidences of adverse events were similar between the GSK and Pfizer vaccines, with no stand out differences between them and several being reported by patients who could not recall which vaccine they had received.

VAERS Data

VAERS data included 3200 reports of adverse events after RSV vaccination among persons aged 60 or older—which did include 28 verified reports of GBS—but 91.2% (n = 2919) of these were classified as nonserious. The most commonly reported events, occurring at a rate above 10%, were erythema (13.2%; n = 384), pain in extremity (13.2%; n = 384), injection site swelling (12.9%; n = 376), headache (12.9%; n = 376), pain (12.8%; n = 373), injection site pain (12.7%; n = 370), and fatigue (12.2%; n = 355). There were 281 series events reported, the most common after GBS being stroke or transient ischemic attack (n = 24), atrial fibrillation (n = 14), or other thrombolytic events (n = 13). Death occurred in 35 instances, of which a reported cause of death was available for 18 individuals—2 of which were attributed to GBS. Those other causes were: acute respiratory distress syndrome, bronchopneumonia, cardiac event, cardiopulmonary arrest, ehrlichiosis, hepatic encephalopathy, hypoxic respiratory failure, multifocal leukoencephalopathy, respiratory failure, rhabdomyolysis, RSV infection, sepsis, sepsis secondary to pneumonia, Pseudomonas bacteremia, varicella-zoster virus meningoencephalitis, and vascular dementia.

V-safe Data

V-safe reporting included 16,220 senior individuals who reported receiving a vaccine and completed at least 1 daily survey. Of those, 39% (n = 6328) reported at least 1 symptom post vaccination, but only 0.4% (n = 68) reported that they received medical care (defined as a doctor appointment or urgent care clinic visit, telehealth, virtual health, or email health consultation, emergency department or emergency department visit, hospitalization, and other options).

The most common symptoms reported in V-safe data, occurring at a rate above 10%, were fatigue or tiredness (20.5%; n = 3327), muscle or body aches (17.5%; n = 2843), headache (15.2%; n = 2460), and fever (10.9%; n = 1765). Notably, though, fever is a self-reported symptom and thus may not reflect the clinical definition. Among those who reported “other” symptoms, 409 selected additional symptoms from a dropdown menu; most commonly selected were sore throat (n = 54), dizziness (n = 38), runny nose (n = 38), cough (n = 27), dizziness upon standing (n = 17), and congestion (n = 16).

Hause and colleagues noted “at least 4 limitations” to this report, the first, being that V-safe reporting is voluntary in nature, and thus data may fail to represent the vaccinated population properly. Similarly, VAERS is a passive surveillance system, and thus can be influenced by reporting biases, underreporting, and incomplete reporting. “Third, VAERS generally cannot determine causal associations between adverse events and vaccination,” they wrote, adding that, “Finally, because these data do not include a comparison group of unvaccinated persons with a similar likelihood of receiving an RSV vaccine, estimating the magnitude of risk for serious but rare outcomes (eg, GBS) after vaccination is not possible.”

Additional Clinical Perspectives

In late 2023, Contagion put together an RSV-focused roundtable discussion with its sister publications, Contemporary OB/GYN and Contemporary Pediatrics, which featured Robert H. Hopkins Jr., MD; William Muller, MD, PhD; Sallie Permar, MD, PhD; Laura Riley, MD; and Neil Silverman, MD. In the fourth installment of the series, the panel evaluated the challenges in providing RSV vaccination to the senior population, including the lack of a “one-size-fits-all” recommendation and risk factors such as heart failure that are more common in this population. Check out their perspectives below.