A new research study found that the effectiveness of the Moderna COVID-19 vaccine declined modestly against the delta and other emerging variants over time, but the vaccine still offered solid protection against severe outcomes. The study, currently in preprint and awaiting peer review, was co-authored by Hung Fu Tseng, PhD, MPH, KPSOM Professor of Health Systems Science and a senior scientist with the Kaiser Permanente Department of Research & Evaluation.
The study of vaccinated individuals from Kaiser Permanente’s Southern California service region showed that the efficacy of the Moderna vaccine declined from 94 percent immediately after vaccination to 80 percent five to six months later. Vaccine efficacy was also lower for people over 65.
“We still see people are very protected against severe outcomes, but against infection overall there is a modest reduction in the [vaccine efficacy] and that suggests that boosters likely do play a role as part of the vaccine strategy,” said Katia Bruxvoort, PhD, an adjunct investigator in the Kaiser Permanente Department of Research & Evaluation, who led the analysis.