People who caught Covid-19 before they were vaccinated had a weaker immune response to the shots than those who never had the virus, potentially leaving them less protected against reinfection, new research shows.
Co-funded by the National Institutes of Health, the study released Monday challenges older research that suggested a prior Covid infection enhanced a vaccinated individual’s immune response — a phenomenon known as hybrid immunity, which some scientists believe provides the best protection against reinfection.
In the study, researchers from Stanford University analyzed how immune cells found in the blood called CD4+ T cells and CD8+ T cells respond to Covid infection and vaccination. Those cells work together to produce an immune response that can help fend off the virus, killing other cells that have been infected.