The level of antibodies in mRNA COVID-19 vaccine recipients' blood may be indicative of the vaccine's efficacy, early findings published Aug. 10 in the preprint server medRxiv suggest.
Researchers measured two types of antibody markers among Moderna vaccine recipients: neutralizing antibodies and binding antibodies, which have both been used as "correlates of protection" for other viral disease vaccines, the study said.
The study included 30,415 people. Half received the COVID-19 shot, while the other half received a placebo. Of those who received the shot, 1,015 had their antibodies measured once after their second dose and again 29 days later.
Those who had higher antibody levels had a lower COVID-19 risk, findings showed. This was true for both neutralizing and binding antibodies. It also held true through 100 days of follow-up, or about four months later.
"Binding and neutralizing antibodies correlated with COVID-19 risk and vaccine efficacy and likely have utility in predicting mRNA-1273 [Moderna's vaccine] vaccine efficacy against COVID-19," researchers said. "Together with evidence from other studies, the current results support that neutralization titer is a potential surrogate marker for mRNA-1273 vaccination against COVID-19 that can be considered as a primary endpoint for basing certain accelerated approval decisions."
Researchers hope the FDA "will see these data and use them as a provisional approval mechanism," Peter Gilbert, study co-author, told USA Today. In place of timely, large scale clinical trials, using antibody measurements as a way to measure vaccine efficacy could help speed up the development and approval process of new vaccines or boosters, researchers said.
They also cautioned that research is ongoing and that the study did not evaluate the role of T cells and B cells, which also play a role in a person's immune response.