COVID-19 variants have been emerging all over the world since the pandemic started. Some mutants arising in the last few months are spreading faster than the SARS-CoV-2 virus seemed capable of previously. Understandably, this has caused concern that the vaccines from Pfizer, Moderna, AstraZeneca, and other biopharma companies that will hopefully bring the pandemic under control won't be as effective.
The B.1.1.7 variant, which was detected in England in September 2020, carries a handful of different mutations, eight of which appear in the spike protein that allows the virus to attach to cells. One mutation, called N501Y, attracts a lot of attention because it sits at the interface between the spike protein and the cell about to be infected.
On top of that, the N501Y mutation itself — where the amino acid asparagine (in biochemical nomenclature simply called "N") at position 501 changed to tyrosine (called "Y") — is a rather significant change in terms of chemistry and size, because tyrosine has a bulky ring of carbons that asparagine lacks. Large rings like tyrosine's can change how areas of the protein around it are shaped. This mutation appears in other SARS-CoV-2 lineages as well. Another mutation in the spike protein, E484K present in the lineage B.1.351 that was first detected in South Africa in October 2020, is not as treatable with monoclonal antibodies.
These changes in the spike protein appear to strengthen the link between the virus and a cell. Since both the already-being-distributed Pfizer and Moderna vaccines target the spike protein, do these mutations alter their efficacy?
Scientists at Moderna and the NIH re-visited serum drawn from either non-human primates vaccinated with Moderna's mRNA-1273 vaccine or humans from vaccine's phase 1 clinical trial. They tested whether that serum could still effectively neutralize different SARS-CoV-2 mutants in comparison to earlier lineages, using non-infectious engineered viruses that had the genetic characteristics of the SARS-CoV-2 virus. They published their results in a preprint on bioRxiv this morning.
The B.1.1.7 virus had little-to-no ability to evade the immune response from vaccinated humans or non-human primates. However, the B.1.351 virus was more difficult to neutralize, requiring about 2 to 10 times more serum than the "original" SARS-CoV-2 virus.
However, all viruses and mutations tested were neutralized in these experiments — none of them escaped, it just took more of the immune response in the serum to do it. This mirrors the success of the Pfizer vaccine, which uses similar mRNA technology to Moderna's and is effective against the B.1.1.7 mutant.