Moderna (NASDAQ:MRNA) shares experienced a sharp decline, dropping as much as 11% in their most significant intraday fall since November, following new data indicating a substantial drop in the efficacy of its RSV vaccine in the second year.
The updated figures reveal that the vaccine's efficacy decreased from 55% in the first year to just 36% in the second year among patients exhibiting at least three "lower respiratory" symptoms of RSV.
This information was disclosed in documents posted on the Centers for Disease Control and Prevention (CDC) website on Wednesday.
In comparison, vaccines from competitors showed stronger performance over the same period.
While Pfizer's RSV vaccine efficacy declined from 86% in the first year to 74% in the second year, GSK's vaccine decreased from 79% in the first year to 59% in the second year.