The mRNA COVID-19 Vaccines Shown to be 94% Efficacious in Health Care Personnel

A new CDC study demonstrates effectiveness in a population with high exposure to the virus.

A new CDC study demonstrated the mRNA COVID-19 vaccines reduced the risk of getting sick with COVID-19 by 94% among health care personnel who were fully vaccinated.

“This report provided the most compelling information to date that COVID-19 vaccines were performing as expected in the real world,” CDC Director Rochelle Walensky, MD, MPH, said. “This study, added to the many studies that preceded it, was pivotal to CDC changing its recommendations for those who are fully vaccinated against COVID-19.”

The assessment compared vaccination status of participants who tested positive for SARS-CoV-2, the virus that causes COVID-19 (cases) with vaccination status of those who tested negative (controls). Among the 1843 participants, there were 623 cases and 1220 controls. Vaccine effectiveness estimates were calculated by comparing the odds of COVID-19 vaccination in cases and controls. The large sample size in this study allowed for a precise vaccine effectiveness estimate with narrower confidence intervals than earlier CDC back in March.

In that study, the findings came from studying nearly 4000 health care personnel, first responders, and other frontline workers from mid-December 2020 through mid-March 2021. The participants were tested weekly for 13 weeks in 8 US locations. In addition, more data from these studies is showing that transmission is unlikely from people who have been vaccinated.

“Among fully immunized (≥14 days after second dose) persons, 0.04 infections per 1000 person-days were reported, and among partially immunized (≥14 days after first dose and before second dose) persons, 0.19 infections per 1000 person-days were reported,” the CDC stated on their website at that time.

In this most recent study, there was an 82% reduction in the risk of getting sick with COVID-19among those who were partially vaccinated, defined in this study as 14 days after being administered the first dose through six days after dose 2.

Not only are the mRNA vaccines highly efficacious, their side effects has shown to be fairly minor and no lasting impacts.