I am one of the lucky few who has not yet tested positive for covid-19. This is despite the fact that for my research I work in contact with sars-cov-2 alive and able to reproduce, I have face-to-face lectures at university and I have children who go to school. I have healthy, fully vaccinated friends of the same age as me, who haven’t been so lucky. And some have fallen ill with covid-19 more than once in the past two years. What does this reveal about my immune system?
Memory Cells First, we need to consider a number of scenarios. There is a very small chance that I have never come into contact with the virus. But given the duration of the pandemic and the number of highly transmissible variants, it’s unlikely. Then there is the possibility that I came into contact with sars-cov-2, but that it was eliminated from my body quickly before it developed and caused the disease (abortive infection). At the beginning of the pandemic, and before I was vaccinated, I may have caught the virus, but I may have been among the few people who did not show symptoms and therefore did not take a test.
Carried out a test.
Some people can clear the virus quickly because they have pre-existing antibodies and cells with an immune memory that recognize the virus. These could be T cells with cross-reactivity, previously generated to fight coronaviruses responsible for the common cold. There is evidence of a higher prevalence of endemic coronavirus (non-covid-19) infections in young people and a reduced presence of cross-reactive T cells in older people.