Respiratory syncytial virus (RSV) vaccines have been an estimated 79% efficient towards harmful virus-related blood clots amongst Medicare recipients within the 2023-24 respiratory virus season, a US Facilities for Illness Management and Prevention (CDC)–led analysis staff experiences in Rising Infectious Illnesses.
Of 15.6 million Medicare fee-for-service beneficiaries aged 65 years and older who have been studied, 58% have been ladies, and 13% had weakened immune programs.
“Respiratory virus infections, together with respiratory syncytial virus (RSV) infections, have been related to elevated danger for myocardial infarction, ischemic stroke, and venous thromboembolism,” the research authors wrote. “In 1 US-based surveillance community, ≈22% of adults >50 years of age who have been hospitalized with RSV skilled an acute cardiac occasion.” They cited a 2024 JAMA Inner Drugs research.
In June 2023, the CDC’s Advisory Committee on Immunization Practices (ACIP) really useful that adults aged 60 years and older obtain a single RSV vaccine dose. The researchers aimed to estimate the vaccine effectiveness (VE) of a single dose towards virus-related thromboembolic occasions on this age-group in the identical season that members obtained the vaccine.
Little to no waning in first 4 months
VE towards RSV-related thromboembolic occasions (coronary heart assault, ischemic stroke, and venous thromboembolism) was 79% (95% confidence interval [CI], 74% to 83%) amongst all members. Estimates didn’t differ considerably between immune-compromised (VE, 69% [95% CI, 56% to 78%]) and never–immune-compromised (VE 82% [95% CI, 77% to 86%]) beneficiaries. The research was underpowered to estimate VE towards every thromboembolic occasion.
As anticipated, RSV vaccines supplied greater safety towards RSV-associated thromboembolic occasions in contrast with all-cause thromboembolic occasions.
Estimated VE towards thromboembolic occasions was 75% (95% CI, 63% to 83%) amongst members aged 65 to 74 years and 80% (95% CI 74%–84%) amongst these aged 75 and older. VE level estimates by time since vaccination have been all inside 4 proportion factors (14 to 59 days, 80% [95% CI, 72% to 86%]; 60 to 119 days, 79% [95% CI, 72% to 84%]; 120 days or later, 75% [95% CI, 60% to 84%]).
VE estimates differed solely barely by model (Arexvy, 76% [95% CI, 70% to 81%]; Abrysvo, 85% [95% CI, 77% to 90%]).
Extending the follow-up interval for thromboembolic occasions produced an estimated VE of 78%, and proscribing analyses to durations of excessive RSV circulation generated a VE estimate of 79%.
Estimates of VE towards all-cause thromboembolic occasions, no matter earlier RSV prognosis, have been decrease (21% [95% CI, 19% to 22%]) than for major analyses. VE towards RSV-related thromboembolic occasions based mostly on fashions with inverse likelihood of remedy weights (IPTW) was 71% (95% CI, 62% to 77%), which was akin to estimates obtained in non-IPTW fashions.
“As anticipated, RSV vaccines supplied greater safety towards RSV-associated thromboembolic occasions in contrast with all-cause thromboembolic occasions,” the investigators wrote. “Time since vaccination outcomes counsel minimal to no waning over the primary 4 months postvaccination. Different analyses of RSV-associated hospitalization demonstrated extra noticeable waning over a shorter interval.”
