ST. LOUIS — Washington University researchers on Monday released a study further suggesting that the Pfizer and Moderna COVID-19 vaccines offer monthslong protection from the virus.
No one had yet studied whether the vaccines create persistent responses in key parts of the lymph nodes, the researchers said. Their data was published Monday in the journal Nature.
"This is evidence of a really robust immune response," co-senior author Dr. Rachel Presti, an associate professor of medicine, said in a statement.
The vaccines have already been studied in large clinical trials. The original Pfizer vaccine trial included nearly 38,000 participants, and tracked the number of vaccinated and unvaccinated individuals who became infected with COVID-19 over the course of months. But the study released Monday looked at the mechanism by which the body responds to the virus.
The researchers looked in structures within lymph nodes called germinal centers, which train immune cells to better recognize the virus and respond. The study included 14 people who received two doses of the Pfizer vaccine.
The Pfizer and Moderna vaccines both use mRNA technology, in order to teach the body's cells to make proteins, or pieces of proteins, that trigger an immune response to the virus.
Samples were taken from the participants just before they received the second dose of vaccine, and again one, two, and four weeks after that.
Of the 14 participants, 10 gave samples 12 weeks after the second dose. Eight of them still had detectable germinal centers producing immune cells against the virus.
The researchers also took blood samples from 41 healthy adults, eight of whom had previously had COVID-19. After vaccination, the individuals who had recovered from a previous infection had the strongest antibody responses.
"We didn't set out to compare the effectiveness of vaccination in people with and without a history of infection, but when we looked at the data we could see an effect," Dr. Jane O'Halloran, co-first author and assistant professor of medicine, said in a statement. "If you've already been infected and then you get vaccinated, you get a boost to your antibody levels. The vaccine clearly adds benefit, even in the context of prior infection, which is why we recommend that people who have had COVID-19 get the vaccine."
