One COVID Vaccine Held Up Best Over Time, CDC Study Suggests

In terms of preventing COVID-related hospitalizations, the two-dose mRNA vaccines from Pfizer (Comirnaty) and Moderna offered the best protection upfront and over time, a case-control analysis involving data from 21 U.S. hospitals showed.

From March to August 2021, the vaccine effectiveness (VE) against COVID-19 hospitalizations landed at 93% for the Moderna vaccine, 88% for Pfizer’s, and 71% for Johnson & Johnson’s (J&J), reported Wesley Self, MD, of Vanderbilt University Medical Center in Nashville, Tennessee, and colleagues, writing in the Morbidity and Mortality Weekly Report.

After 120 days from the time of vaccination, however, Moderna’s VE against hospitalization only dipped to 92%, a non-significant decline, while Pfizer’s dropped to 77% (P<0.001).

“Differences in VE between the Moderna and Pfizer-BioNTech vaccine might be due to higher mRNA content in the Moderna vaccine, differences in timing between doses (3 weeks for Pfizer-BioNTech versus 4 weeks for Moderna), or possible differences between groups that received each vaccine that were not accounted for in the analysis,” Self and co-authors suggested.

No data were shown for the J&J shot after 120 days due to the limited number of patients who received the vaccine, but the VE rate dipped to 68% for the single-dose vaccine after 28 days.

A second analysis in the study, involving 100 patients, showed that individuals vaccinated with the one-dose J&J viral vector vaccine had lower anti-SARS-CoV-2 antibody levels at 2 to 6 weeks after being fully vaccinated compared with the mRNA vaccine recipients. Antibody levels were slightly higher with Moderna’s versus Pfizer’s.

“Although an immunologic correlate of protection has not been established for COVID-19 vaccines, antibody titers after infection and vaccination have been associated with protection,” the group wrote.

The findings came from a sample of 3,689 adults without immunocompromising conditions (1,682 case patients and 2,007 controls) admitted with COVID-19 to one of 21 U.S. hospitals across 18 states from March 11 to August 15. Median patient age was 58 years and a little less than half were women, while 53% were white, 23% were Black, and 18% were Hispanic.

Overall, 20% were fully vaccinated with Pfizer’s vaccine, 12.7% with Moderna’s, and 3.1% with the J&J vaccine; 64.0% were unvaccinated.

Limitations of the study included that it was limited to non-immunocompromised adults, the limited number of J&J recipients, and that follow-up time after being fully vaccinated was only about 29 weeks. Notably, data on VE were not evaluated by SARS-CoV-2 variant, including the Delta variant.