Top mRNA COVID-19 Vaccines 94% Effective, New CDC Data Shows

May 17, 2021 - A multisite test-negative design case-control CDC study recently found that the mRNA COVID-19 vaccines from Pfizer and Moderna are highly effective against symptomatic coronavirus.

The study analyzed the effectiveness of vaccines administered to healthcare personnel (HCPs). The trial enrolled 623 case-patients and 1,220 controls between 19 and 49 years of age. The majority of HCP worked in occupational categories with substantial anticipated direct patient contact. 

Nearly 78 percent of participants received the Pfizer-BioNTech vaccine, BNT162b2, while the remainder received COVID-19 Vaccine Moderna.   

Researchers found that effectiveness of a single-dose of either BNT162b2 or COVID-19 Vaccine Moderna was 82 percent against symptomatic coronavirus, while a two-dose regimen was 94 percent effective.  

CDC’s results were consistent with outcomes of two cohort studies of Pfizer and BioNTech’s COVID-19 vaccine among HCP. For example, BNT162b2 was 80 percent effective two weeks after the first dose in a US cohort study and 72 percent effective 21 days after the first dose in a UK study. 

But overall effectiveness of a single-dose of BNT162b2 was higher than the estimated effectiveness found in the Pfizer- BioNTech clinical trial. Among 36,523 participants who received BNT162b2 in December, efficacy against the coronavirus for HCP was just 52 percent.

While in a March study, the Israel Ministry of Health (MoH) found that the vaccine was 57 percent and 66 percent effective among the general adult population depending on timing. These numbers were taken 14 to 20 and 21 to 27 days, respectively, after the first dose. 

“Complete vaccination with authorized mRNA COVID-19 vaccines is highly effective in preventing symptomatic COVID-19 among HCP, supporting the results of phase III trials and additional accruing evidence in recent observational studies,” researchers said in the study.

“Real-world data are critical to guiding evolving COVID-19 vaccine policy. In addition to adherence to recommended infection control and prevention practices, a critical component of controlling the U.S. COVID-19 pandemic and protecting HCP is ensuring high coverage with safe and effective COVID-19 vaccines,” they continued. 

Throughout the COVID-19 pandemic, HCP have been at high-risk for exposure to COVID-19 through patient interactions and community exposure.

In a similar CDC study from March, researchers used real-world evidence to find that mRNA COVID-19 vaccines were highly effective in preventing COVID-19 infections among healthcare personnel, first responders, and other essential workers. 

The study evaluated BNT162b2 and COVID-19 Vaccine Moderna in 3,950 study participants over a 13-week period from December 2020 to March 2021. 

Researchers found that risk of infection was reduced by nearly 80 percent two or more weeks after the first dose and by 90 percent two or more weeks after the second dose.  

The results from the CDC study were consistent with the Phase 3 clinical trials from both Pfizer and BioNTech as well as Moderna, which were all conducted before the vaccines received FDA emergency use authorization.

At the end of November, Pfizer and BioNTech concluded their trial after BNT162b2 was found to be 95 percent effective in participants with prior COVID-19 infection, as well as without Shprior infection. 

And just a month later, Moderna announced that a second primary analysis of its COVID-19 vaccine, mRNA-1273, showed that it was 94.1 percent effective against the coronavirus. 

Advisory Committee on Immunization Practices recommended in December prioritization of HCP for coronavirus vaccination to maintain provisions of critical services and reduce spread of infection in healthcare settings. 

For example, the committee stated that in Phase 1b, COVID-19 vaccines should be offered to individuals 75 years of age and older and non-healthcare frontline essential workers. And Phase 1c should offer COVID-19 vaccines to individuals 65 to 75 years of age, individuals 16 to 64 years of age with high-risk medical conditions, and essential workers not included in Phase 1b.