An Israeli study that found a robust immune response from recovered COVID-19 patients who were vaccinated provides “some of the first real-life evidence” that immunity lasts even if antibody levels appear to drop, a leading researcher said Thursday.
Most vaccines work by first “showing” a copy of the coronavirus to a body’s immune system with the first dose, allowing it to learn how to fight it off.
The second dose introduces an antigen that is designed to provoke a large response by virus-fighting antibodies, which rush to protect the body and create phalanxes of copies ready to do battle should the real SARS-COV-2 show up.
People who have already been infected have these virus-fighting antibodies once they recover, but testing has shown that the antibodies eventually fade, leading to fears of re-infection.
However, researchers at Ziv Medical Center in the Galilee city of Safed found that a small sample of recovered patients who were given a first dose of a coronavirus vaccine had the full-scale immune response that most people only have upon receiving a second dose.
Their bodies produced so many new antibodies after the first shot that within 21 days — until just before the second shot is administered — their average antibody levels stood at 10 times those of other vaccinees.
“It’s what we call a ‘boost-like’ response as opposed to what we call the prime response, meaning the first time the body encounters the antigen,” said Prof. Michael Edelstein, a Bar-Ilan University epidemiologist who led the research.
The study by Edelstein’s team was published Thursday in the peer-reviewed journal Eurosurveillance. It suggests that the immune system of recovered patients remembers SARS-CoV-2 well, and has a high degree of lasting protection.
The new study indicates that the current assumption that recovered patients have around 82% immunity is valid for at least 10 months, and regardless of antibody levels, Edelstein said. Reinfection, while receiving much media attention, is a rare phenomenon, he added.
“People have been worried because some patients who were infected end up with negative tests for antibodies, and this can cause anxiety with people fearing reinfection,” Edelstein said. “Our study points to continued protection, whether or not antibodies are detectable.”
The study examined antibody levels of 514 staff members at Ziv before and after receiving a vaccine. Medics, unlike the general population, can still get a vaccine if they are recovered patients, and 17 people had previously been infected, between one month ago and 10 months ago.
The majority of the recovered patients — 11 out of 17 — no longer had antibodies, but all 17 showed the strong immune response after the first shot that is normally witnessed only after the second.
“There was no real difference between the response of the most recent patients and those who had coronavirus months ago, which is encouraging for immunity,” Edelstein stated.
It’s not yet clear if the same powerful rush of antibodies would show up in those who receive the vaccine after having had an asymptomatic infection.
Edelstein said that following his small study he hopes this finding will be investigated in a larger cohort, and said that if his findings are corroborated, they may impact policy as well as reassure recovered patients.
“This may suggest that, in terms of vaccination policy, recovered people only need a single shot of the vaccine, which could save significant amounts of money,” he said.