The emergence of Omicron has sparked much speculation that it may be more resistant to Covid-19 vaccines than existing variants, including Delta. But what does this mean for the average double vaccinee?
All of the vaccines currently available in the UK work by training the immune system against the coronavirus spike protein – the key it uses to infect cells by binding to the ACE2 receptor. Omicron has over 30 mutations in this protein, including 10 in what is called the “receptor binding domain” (RBD) – the specific part that attaches to this receptor. Delta has two RBD mutations.
However, even with all of these changes, there will still be areas (epitopes) that antibodies and T cells – which develop in response to a previous infection or vaccination – will be able to respond to.
“If you scribble the mutations on a picture of the spike protein’s crystal structure and link that to all of the major antibody activities that we know of, that sounds a little terrifying – like, most of your targets of neutralizing antibodies will be torn to pieces, so what will remain of your immune protection? Said Danny Altmann, professor of immunology at Imperial College London.
“And yet the polls we get from South Africa seem to say it doesn’t sound like a big deal, and the people who go to the hospital are unvaccinated rather than vaccinated, as if vaccination always bought. [them] coverage.
Then there are the T cells – immune cells that recognize and attack cells infected with the virus, and inform the antibody-producing B cells of the viral risk they face.
“We all think T cells can see the differences [between variants], and that the T cell repertoire is much more impermeable there, which may also offer you some protection, ”said Altmann.
The question is, how much protection? We know that people who have received a double bite can be infected with the Delta variant – although the chances of this happening are about three times lower than if they had not been vaccinated. More importantly, people who are vaccinated are about nine times less likely to die if they become infected.
Although it appears that infection with Omicron is even more likely, Professor Paul Morgan, immunologist at Cardiff University, said: “I think blunt rather than complete loss. [of immunity] is the most likely outcome.
“The virus cannot lose every epitope on its surface, because if it did, this spike protein could no longer function. So while some of the antibodies and T cell clones made against earlier versions of the virus or against vaccines may not be effective, there will be others, which will remain effective.