Respiratory syncytial virus viral vaccine under research.
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A single dose of the shot was 67.2% effective in preventing lower respiratory tract illness over two RSV seasons, according to new results from a phase three clinical trial. That’s compared with 82% after one viral season, which typically lasts from October to March in the Northern Hemisphere.
The shot was also 78.8% effective against severe RSV disease after two seasons, compared with 94% after one season. Severe disease refers to cases that prevent normal, daily activities.
The London-based company said high efficacy was similarly maintained in older adults with underlying conditions, who are most at risk of severe RSV.
GSK also evaluated the effectiveness of an annual vaccination schedule, which involves administering a second dose of its shot after a year. The company said the cumulative efficacy of two doses was 67.1%, “suggesting revaccination after 12 months does not appear to confer additional benefit for the overall population.”
That means the vaccine may only need to be administered every other year, which could give GSK an edge over RSV shot rivals such as Pfizer and make it easier for seniors to protect themselves against the virus.
RSV usually causes mild, cold-like symptoms. Each year the virus kills between 6,000 and 10,000 seniors as well as a few hundred children younger than 5, according to the Centers for Disease Control and Prevention.
GSK presented the results to an advisory committee of the CDC on Wednesday. The committee will form a recommendation on when and how often the company’s RSV shot — and a vaccine from rival Pfizer — should be administered in the U.S.
The Food and Drug Administration approved GSK’s vaccine in May, making it the world’s first authorized shot against RSV.
Pfizer’s RSV shot became the second to win approval shortly after. The company also presented new clinical trial data on its vaccine Wednesday.
That shot was roughly 49% effective against lower respiratory tract illness with two or more symptoms after 18 months, which is a steep decline from the shot’s 66.7% efficacy at one year.
Neither drugmaker has established a list price for its vaccine.