The study is one of the first to demonstrate that while a person may recover from COVID-19 infection, they can still suffer lasting damage to their immune system. The findings suggest that previous coronavirus infections can have long-term implications for immunity and could explain why some people become more susceptible to reinfection. The researchers analyzed blood samples from 41 patients who had recovered from COVID-19 in California between March and April — about eight weeks after their initial diagnosis. They compared these with blood samples taken from 34 individuals who had not been infected with SARS-CoV2 at any point before the study’s start date. What they found was startling: Despite all of the participants being healthy again, those previously infected by SARS-CoV2 contained significantly fewer high-quality CD8+ T cells than those without a coronavirus infection — suggesting an impaired immune system response linked directly to surviving COVID-19.
The first group was individuals who had recovered from COVID-19 and were previously infected, the second group was people who had been vaccinated against the virus, and the third group consisted of healthy individuals. The researchers found that those in the recovery group had significantly lower levels of CD8+ T cells than the other groups—even after they’d been given time to recover from their illness. This could indicate that something happened during infection to damage or suppress these particular immune cells, explaining why so many people have lingering symptoms even months after recovering from COVID-19.
The second group, those previously infected with the virus and received two vaccine doses, experienced the greatest decrease in active cases. This suggests that people who have recovered from COVID-19 may benefit even more from being vaccinated than those who are unvaccinated or never exposed to the virus. Additionally, this study is encouraging because it provides evidence for herd immunity against SARS-CoV-2. As more and more individuals become vaccinated, it could significantly reduce new cases of COVID-19 and improve outcomes for people at risk due to underlying health conditions or age factors.
Finally, this group had the highest rate of severe cases, hospitalizations, and deaths due to COVID-19. Unvaccinated individuals must take preventive measures such as wearing masks, socially distancing, and washing their hands frequently. Although these measures help reduce the risk of becoming infected with COVID-19, it is still possible to contract the virus; therefore, getting vaccinated when available should be a priority for those in this group. Vaccination will provide additional protection against more severe forms of disease from COVID-19 and protect vulnerable populations who may not have access to preventative care.
Davis and colleagues are now studying how long the vaccine-induced immunity may last and which mRNA vaccines can induce other immune responses. Their work is part of developing more effective, longer-lasting vaccines to protect against future pandemics. And while Davis acknowledged that there’s still a lot of research to do, he said it was exciting to have this first glimpse into a population that could benefit from these new technologies.