Moderna says its RSV shot is 50% effective across a second season

NEW YORK (Reuters) - Moderna Inc respiratory syncytial virus (RSV) shot mRESVIA showed 50% efficacy in preventing RSV after 18 months, the drugmaker said on Wednesday.

In their clinical trials, GSK's RSV vaccine Arexvy was 78% effective in preventing severe RSV over a second year and Pfizer's was 78% effective through a second RSV season.

Moderna presented the data at a meeting of the U.S. Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices. The drugmaker has previously cautioned against comparing its vaccine to rivals, noting that the trials were not head-to-head and used different case definitions for RSV disease.

(This story has been corrected to eliminate the word 'midway', to reflect that Pfizer's data was from the end of the season, in paragraph 2)

(Reporting by Michael Erman)