This article about so-called hybrid immunity due to infection followed by vaccination is somewhat interesting. I find myself wondering how many of the deaths of unvaccinated people due to a second COVID infection could be avoided.
>>>Not long after countries began rolling out vaccines, researchers started noticing unique properties of the vaccine responses of people who had previously caught and recovered from COVID-19. “We saw that the antibodies come up to these astronomical levels that outpace what you get from two doses of vaccine alone,” says Rishi Goel, an immunologist at the University of Pennsylvania in Philadelphia who is part of a team studying super-immunity — or ‘hybrid immunity’, as most scientists call it.
Initial studies of people with hybrid immunity found that their serum — the antibody-containing portion of blood — was far better able to neutralize immune-evading strains, such as the Beta variant identified in South Africa, and other coronaviruses, compared with ‘naive’ vaccinated individuals who had never encountered SARS-CoV-2
2. It wasn’t clear whether this was just due to the high levels of neutralizing antibodies, or to other properties. . . .
The most recent studies suggest that hybrid immunity is, at least partly, due to immune players called memory B cells. The bulk of antibodies made after infection or vaccination come from short-lived cells called plasmablasts, and antibody levels fall when these cells inevitably die off. Once plasmablasts are gone, the main source of antibodies becomes much rarer memory B cells that are triggered by either infection or vaccination. . . .
As breakthrough infections caused by the Delta variant stack up, researchers including Nussenzweig are keen to study the immunity in people who were infected after their COVID-19 vaccinations, rather than before. An individual’s first exposure to influenza virus biases their responses to subsequent exposures and vaccinations — a phenomenon called original antigenic sin — and researchers want to know if this occurs with SARS-CoV-2.
Those studying hybrid immunity stress that — whatever the potential benefits — the risks of a SARS-CoV-2 infection mean that it should be avoided. “We are not inviting anybody to get infected and then vaccinated to have a good response,” says Finzi. “Because some of them will not make it through.” <<<
People who have previously recovered from COVID-19 have a stronger immune response after being vaccinated than those who have never been infected. Scientists are trying to find out why.
www.nature.com
