The data are still coming in, but so far it looks like the Pfizer and Moderna vaccines are close to equally protective for the new UK strain. It’s also looking like both vaccines are less effective against the south African strain because some of the mutations on that variant code for the protein coat (that’s the queue that the immune system uses to build antibodies, B cells and T cells (see our discussion of the immune system in these previous posts Part I and Part II). 

Because there is a wide margin of safety for the protective threshold of neutralizing antibody action against the virus- the vaccine is still protective of that strain as well (although at a lower level- perhaps 70% protective against infection or so).

A new study was published this week entitled mRNA Vaccine-elicited Antibodies to SARS-CoV-2 and Circulating Variants. You can read the study yourself, but basically they found that people who have been vaccinated had high antibody titer levels of IgM, and IgG that are highly effective at neutralizing the virus. Interestingly, it found no difference in the memory B cells when comparing people that were fully vaccinated compared to people with a natural infection.

They found that the UK (B1.1.7/501Y.V1), South Africa (501Y.V2) and Brazil (B1.1.28/501.V3) have a reduced antibody neutralization potency compared to the classic strain.  However, those differences had “comparatively modest” effects on viral sensitivity.

The study does forecast, however, that:

it is possible that these mutations and others that emerge in individuals with suboptimal or waning immunity will erode the effectiveness of natural and vaccine elicited immunity. The data suggests that SARS-CoV-2 vaccines may need to be updated and immunity monitored in order to compensate for viral evolution.”