NEW YORK, June 26 (Reuters) - Moderna Inc ( MRNA )

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 midway through a second RSV season.

Moderna ( MRNA ) 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.