RSV vaccine remains effective across two seasons, study shows
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Key takeaways:
- GSK’s RSV vaccine was approved by the FDA in May for older adults.
- The vaccine was effective across two full RSV season in adults aged 60 years or older.
BOSTON — GSK’s respiratory syncytial virus vaccine had a sustained effectiveness of around 67% among adults aged 60 years or older across two full RSV seasons, researchers reported at IDWeek.
“RSV is a major cause of hospitalization and mortality in older adults, resulting in over 177,000 hospitalizations due to RSV and over 14,000 deaths per year,” Michael G. Ison, MD, MS, chief of the Respiratory Diseases Branch at the National Institute of Allergy and Infectious Diseases, said during a presentation at IDWeek.
“While the disease can occur in any older adult, it is worse in patients [who] are over 65 years of age; patients with underlying comorbid conditions including primary vascular, lung, kidney and liver disease as well as diabetes; and those patients [who] are immunocompromised,” Ison said.
GSK’s RSV vaccine was approved by the FDA in May and is one of two licensed RSV shots in the U.S.
Data leading to the licensure showed that the vaccine was 82.6% effective against RSV-related lower respiratory tract disease (RSV-LRTD) and 94.1% effective against severe RSV-related lower respiratory tract disease, which held up across age groups and comorbidities, Ison noted.
To assess effectiveness across two RSV seasons, Ison and colleagues conducted a phase 3, placebo-controlled, multicountry study of adults aged 60 years or older, who they randomly assigned in a 1:1 ratio to receive GSK’s vaccine or a placebo before the first RSV season.
They then randomly reassigned participants who had been vaccinated — again in a 1:1 ratio — to receive a second dose of the vaccine or a placebo before the second RSV season. They assigned participants who had received a placebo before the first season to receive an additional placebo dose before the second season.
Ison and colleagues assessed vaccine efficacy (VE) against first occurrence of RSV-LRTD, severe RSV-LRTD, RSV-LRTD by age, baseline comorbidity and frailty status, and RSV-related acute respiratory illness across the two seasons.
In total, they included 24,967 participants in the VE analyses — 6,242 who received two doses, 6,227 who received one dose, and 12,498 who received a placebo twice. Overall, the study found that the VE of a single dose of the vaccine against RSV-LRTD over two seasons was 67.2% (97.5% CI, 48.2%-80%). VE over two seasons among participants who received two doses was 67.1% (97.5% CI, 48.1%-80%).
During his presentation, Ison said that he was surprised that there was not much of a boosting effect after a second dose. He explained, though, that a different study assessing antibody levels among patients who received either a single dose or multiple doses showed that at month 12, there were “relatively similar levels at a relatively high titer.”
“I think that what this tells us is that we have generated a pretty robust vaccine response that's maintained at least for greater than a year,” he said.
Additionally, the study demonstrated sustained VE against severe RSV-LRTD, RSV-LRTD among adults aged 60 to 79 years and those with at least one baseline comorbidity of interest, pre-frail participants, and against RSV-related acute respiratory illness.
Ison said there are additional studies underway to assess persistence and the best timing for revaccination.
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Ison MG, et al. Abstract 1936. Presented at: IDWeek; Oct. 11-15, 2023; Boston.
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