COVID-19 study quantifies antibody response to Pfizer, Moderna

On Sep 3, 2021

A new study out of the University of Virginia School of Medicine shows that antibody levels in recipients of the Moderna COVID-19 vaccine were slightly higher than recipients of the Pfizer vaccine.

The difference was mostly noted in relatively older subjects. Researchers took blood samples from 167 vaccinated UVA employees one week to 31 days after their second dose. Some 79 were inoculated with the Pfizer vaccine, 88 with the Moderna vaccine. The average age of participants was 42, 38% were 50 or older, and 72% of them were women.

As doctors and scientists try to understand this virus and how to respond to it, UVA’s study provides a small but significant piece to the puzzle. However, researchers cautioned against drawing conclusions about the vaccines’ effectiveness based purely on antibody data.

They said that both vaccines performed “exceptionally” after being given to millions of people around the world.

Israelis above 60 years old receive their third dose of the COVID-19 vaccine at a Clalit health care maintenance organization, on August 08, 2021 in Jerusalem. (credit: OLIVIER FITOUSSI/FLASH90)

Moderna and Pfizer both use mRNA (messenger RNA) to teach the immune system how to defend itself against COVID-19‘s spike protein, which is unique to the virus.

Though both vaccines are similar, the chemical formulations differ slightly, with Moderna using more mRNA than Pfizer. This provided the catalyst for researchers to quantify and compare the antibody responses to the vaccines.

The results were that the antibodies in Moderna were 68.5 micrograms per milliliter (µg/mL), and 45.9 for Pfizer.

To study the effect of age on antibody response, researchers divided participants into those younger than 50 and those older…