RSV Vaccine Maintains Efficacy Across Two Seasons in Seniors

BOSTON — Efficacy of GSK’s respiratory syncytial virus (RSV) vaccine held strong through two RSV seasons in adults 60 and over, according to new results from the company’s pivotal trial.

With a single dose, efficacy of the RSV perfusion F protein vaccine (Arexvy) against RSV-related lower respiratory tract disease declined from 82.6% during the first season to 67.2% through the first and second seasons combined, reported Michael Ison, MD, of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland.

Efficacy against severe cases, meanwhile, dipped from 94.1% to 78.8%, respectively, Ison said in a presentation at the IDWeek annual meeting.

Efficacy over the two seasons was consistent across age groups and for patients at high risk, he reported:

• Ages 60-69 years: 65.4%
• Ages 70-79 years: 74.9%
• Patients with comorbidities: 66.7%
• Pre-frail patients: 73.3%

However, “revaccination after 1 year did not seem to provide additional efficacy benefit for the overall study population,” Ison said. “The clinical development program will further evaluate persistence of efficacy and the optimal timing for revaccination.”

Arexvy gained FDA approval in May based on results through one RSV season from the current phase III trial, AReSVi-006.

“The data we heard at this session suggest that RSV vaccine efficacy is going to last for more than a season,” Rajesh Gandhi, MD, of Massachusetts General Hospital/Harvard Medical School in Boston, told MedPage Today. “For now, I am telling my patients that we should wait until we get formal guidance from the CDC Advisory Committee on Immunization Practices [ACIP] on how frequently to receive the vaccine.”

In June, ACIP recommended either the GSK or Pfizer RSV vaccine for adults 60 and up via a shared decision-making process.

“We don’t know yet if they are going to recommend it annually or at a greater interval,” said Gandhi. “The data presented here looks promising that the RSV vaccine will provide protection for longer than a single season, which is different from the influenza vaccine, which is a yearly shot.”

In AReSVi-006, about 55% of the nearly 25,000 participants were ages 60-69, while around 36% were ages 70-79, and about 8% were 80 or older. About 79% of the study population was white. Most (60%) were considered fit, while around 1.5% of the cohort was diagnosed as being frail at trial onset and 30% considered pre-frail.

Through the two seasons, there were 30 cases (17 severe) among 12,466 people who received the vaccine versus 139 cases (48 severe) among 12,494 people on placebo.

At the end of year 1, some patients were randomized to receive a second inoculation. With the second dose, efficacy against RSV-related lower respiratory tract disease or severe cases was essentially identical compared with the initial dose alone.

For adverse events (AEs), the authors reported that the frequencies of solicited AEs after the second dose were similar to those after the first dose, including erythema, pain, swelling, fatigue, fever, and headache. Most of the AEs were mild or moderate and tended to resolve within 2 or 3 days, Ison reported.

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