Covid-19: Pfizer vaccine could provide lasting immunity, small study suggests

New research looking at the Pfizer BioNTech covid-19 vaccine has provided early indication that it’s likely to produce strong and lasting immunity, although the findings are based on a small number of people.1

Researchers from Washington University School of Medicine in the US looked at the antigen-specific B cell responses in peripheral blood (for 41 people) and draining lymph nodes (for 14 people) who received two doses of Pfizer vaccine.

The study, published in Nature, found that nearly four months after the first dose, people who received the Pfizer vaccine still had germinal centres in their lymph nodes producing plasma and memory B cells directed against the SARS-CoV-2 virus.

Lead author Ali Ellebedy, who is associate professor of pathology and immunology at Washington University, said, “Germinal centres are where our immune memories are formed. And the longer we have a germinal centre, the stronger and more durable our immunity will be because there’s a fierce selection process happening there, and only the best immune cells survive.

“We found that germinal centres were still going strong 15 weeks after the vaccine’s first dose. We’re still monitoring the germinal centres, and they’re not declining; in some people, they’re still ongoing. This is truly remarkable.”

Researchers extracted cells from 14 people who had no history of covid-19 infection three weeks after the first dose—just before the second dose—and at weeks four, five, and seven. Ten participants provided additional samples 15 weeks after the first dose.

Three weeks after the first dose, all 14 people had formed germinal centres with B cells producing antibodies that target SARS-CoV-2. The response expanded greatly after the second dose and remained high. At 15 weeks after the first dose, eight of the 10 participants still had detectable germinal centres containing B cells targeting the virus.

The research team also took blood samples from 41 people who received the vaccine, including eight who had previously been infected with the virus. Samples were obtained before each dose of the vaccine, as well as at weeks four, five, seven, and 15 after the first dose.

In people without prior exposure to the virus, researchers found that antibody levels rose slowly after the first dose and peaked one week after the second, while in people who had previously been infected—and therefore already had antibodies in their blood before vaccination—their antibody levels peaked higher than the uninfected participants’.

Manufacturers of the two mRNA covid-19 vaccines—Pfizer and Moderna—have previously reported that their vaccines provide protection against the virus for at least six months, based on tracking whether vaccinated people became infected with covid-19. But this new study is the first to look at how the immune response was developing in the body, which may provide some insight into the strength and persistence of the response for years to come.

The paper said, “The persistence of S-binding germinal centre B cells and plasmablasts in draining lymph nodes is a positive indicator for induction of long lived plasma cell responses. Elicitation of high affinity and durable protective antibody responses is a hallmark of a successful humoral immune response to vaccination. By inducing robust germinal centre reactions, SARS-CoV-2 mRNA based vaccines are on track for achieving this outcome.”