I'm one of the lucky people who haven't tested positive for Covid. This is despite the fact that I teach face-to-face, have school-age children, and work with live replicating the virus that causes Covid.
Some of my healthy friends have suffered from more than one case of Covid in the past couple of years, and they were not so lucky. What does this tell me about my immune system?
We have to think about a number of scenarios. There is a chance that I have not come into contact with the virus. This is not likely given the duration of the epidemic and the number of highly transmissible variants. There is a chance that I have come into contact with the disease, but it was cleared from my body quickly. I could have caught the virus but I didn't test for it because I didn't have any symptoms.
Some people can clear the virus quickly because they have pre-existing immunity. These could be T-cells that were previously used to fight coronaviruses that cause the common cold. Older people have less cross-reactive T-cell presence than young people, and there is evidence of higher prevalence of endemic coronaviruses in the young.
I received my first and second doses of vaccine, along with a booster shot. Vaccines work by introducing our immune system to the virus and setting off an early arsenal of T-cells. These leave memory cells behind, which can persist for years and prevent reinfection.
Every time there is a new variant of Covid vaccine, scientists frantically search for any evidence of vaccine escape in real-life data. We can't predict vaccine escape because we aren't observing stepwise virus evolution, where emerging strains add new mutations to their predecessors, and the Omicron variant has few similarities with Delta. Natural infections do not offer long-term protection, and the more potent vaccine-induced immunity needs a booster to protect against variant.
I am not sure if I would be immune to the next variant if I had previously caught one variant. People report different symptoms after different infections, some doing better and some worse.
There is a chance that the immune systems respond differently to the virus. The spikeProtein on the surface of the virus needs to stick to the target cells, like theACE2Protein. Is it possible that those who are resistant to infections have different levels of ACE2? The expression of ACE2 in the lungs of children is related to their age.
It is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556 Polymorphisms are differences in the expression of a specific type of molecule. People who have a rare genetic polymorphism for the CCR5 have been immune to HIV. Recent genetic analyses show that rare types of ACE2 may affect susceptibility to Covid.
Studies in healthcare workers who consistently remained negative for Covid showed the presence of pre-existing T-cells that recognise peptides, the chain of molecules that make up a protein from less variable parts of the virus. It would be wise to not rely on spike-targeting vaccines if we want to induce immunity to new variants, and we should think about incorporating more parts of the virus that don't change over time.
We can't be sure why someone like me hasn't tested positive yet. There is no guarantee that I will develop Covid still because of the likelihood of emerging variant. Don't take your chances, even if you've been lucky so far.
Dr Zania Stamataki is a senior lecturer at the University of Birmingham.
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