A recent analysis by the Centers for Disease Control and Prevention (CDC) has provided an early safety profile of respiratory syncytial virus (RSV) vaccines in adults aged 60 years and older. The findings, which cover vaccinations administered between May 3, 2023, and April 14, 2024, indicate that while most reported side effects were mild, continued monitoring for rare but serious adverse events is warranted.
V-safe Surveillance Data
The CDC's V-safe surveillance system, a voluntary program where participants report symptoms via web surveys, included 16,220 individuals aged 60 years and older who received an RSV vaccine. The median age of participants was 70 years, and 59.7% were women. Among these, 39% reported symptoms they considered possibly related to the RSV vaccination. Injection site symptoms were more frequent with the GSK vaccine (43.9%) compared to the Pfizer vaccine (20.3%). Systemic symptoms followed a similar trend, with 36.6% reporting after GSK and 21.6% after Pfizer vaccination. The most common symptoms reported were pain at the injection site (31.0%), fatigue (20.5%), and muscle aches (17.5%).
Approximately 7.8% of participants reported being unable to perform normal daily activities due to these symptoms, and 0.4% sought medical care. Of those seeking medical care, five submitted reports to the Vaccine Adverse Event Reporting System (VAERS).
VAERS Data Analysis
The VAERS database received 3,200 reports of adverse events in the specified age group following RSV vaccination. Of these, 68.5% were associated with the GSK vaccine and 28.7% with the Pfizer vaccine. The majority (91.2%) were classified as non-serious, with common events including pain in an extremity (13.2%), headache (12.9%), and fatigue (12.2%).
However, 8.8% of the reports were classified as serious, including hospitalizations (6.8%), life-threatening illnesses (2.5%), permanent disabilities (2.1%), and deaths (1.1%). Clinical review of serious reports identified conditions such as stroke or transient ischemic attack (24 cases), Guillain-Barré syndrome (GBS) (37 cases, 28 meeting the case definition), atrial fibrillation (14 cases), and immune thrombocytopenia (11 cases).
Guillain-Barré Syndrome (GBS) Signals
Among the 28 confirmed GBS cases, 13 followed GSK vaccination (1.8 reports per 1 million doses administered), and 15 followed Pfizer vaccination (4.4 reports per 1 million doses administered). This elevated reporting rate of GBS following RSV vaccination necessitates continued surveillance and investigation.
Mortality Data
Eighteen death reports had sufficient information for review. The reported causes of death varied, including acute respiratory distress syndrome, cardiac events, and infections. Two deaths were associated with GBS.
Conclusions
The CDC's early safety analysis suggests that RSV vaccines are generally well-tolerated among older adults, with most reported adverse events being mild to moderate. However, the identification of serious events, particularly GBS, warrants ongoing monitoring and further investigation to fully characterize the risk-benefit profile of these vaccines.
