Researchers claimed in a study published in the journal Immunity that covid infection prior to receiving vaccine jabs can reduce an individuals immune functions. The researchers from Stanford University revealed that the magnitude and quality of the response produced by key immune cells to vaccination were significantly lower in people with prior SARS-CoV-2 infection compared to people without prior infection.

Also, compared to vaccinated individuals who had never been exposed to Covid 19, the level of crucial immune cells that attack the SARS-CoV-2 spike protein was markedly lower in unvaccinated individuals with Covid 19. Crucially, it showed that those who have recovered from the SARS-CoV-2 infection and subsequently received the vaccine are better protected than those who have not.

The researchers created a highly sensitive tool to examine how immune cells known as CD4+ T cells and CD8+ T cells respond to SARS-CoV-2 infection and vaccination. The researchers examined the CD4+ and CD8+ T-cell responses in blood samples from three volunteer groups. One group received two doses of the Pfizer-BioNTech Covid-19 vaccination while the other had never been exposed to SARS-CoV-2. The second group had two doses of the vaccination and was previously infected with SARS-CoV-2. The third group was unvaccinated and carrying Covid-19.

The researchers discovered that vaccinating people who had never been infected with SARS-CoV-2 induced robust CD4+ and CD8+ T-cell responses to the virus spike protein. People who had been infected with SARS-CoV-2 prior to vaccination, on the other hand, produced more spike-specific CD8+ T cells than vaccinated people who had never been infected. Overall, these findings of the study suggested that SARS-CoV-2 infection damages the CD8+ T cell response. 

(Source: https://nypost.com/2023/03/23/covid-19-damages-immune-response-for-some-a-big-deal/ )