More positive news comes from Pfizer and BioNTech this week as the latest results from their clinical trial data suggest that their vaccine protects against the more contagious B.1.351 variant initially detected in South Africa. The vaccine showed 100 percent efficacy in South Africa, where B.1351 is prevalent. Nine people in the study contracted Covid-19, all of whom were in the placebo group. However, these findings are limited as only 800 participants were enrolled in South Africa. Nonetheless, this is a very positive result and very different from the response of the AstraZeneca vaccine to the B.1.351 variant which recent studies showed only 10.4% efficacy against mild-to-moderate infections. The difference could be related to the amount of antibody titers produced by both vaccines, as although they are both reacting to the same antigen, the concentration of neutralizing antibodies is generally much higher in the Pfizer and Moderna vaccines than it is for the adenovirus vaccines.
However, the challenges in protecting the population against the ever-evolving variants remain complex, especially with regards to the unknown duration of protection. A study published this month takes a different approach to protection, asking the question do antibodies generated by infection with a variant protect against other strains.
The study used plasma collected from adults hospitalized with Covid-19 who were infected with two South African infection waves, with the second wave dominated by the B.1.351 variant. Sequencing demonstrated that infections in first wave plasma donors did not have any of the B.1.351 defining mutations, except for one with the E484K mutation in the receptor-binding domain.
The B.1.351 virus was effectively neutralized by plasma from second wave infections and the first wave virus (SARS-CoV-2) was effectively neutralized by first wave plasma. However, in cross-neutralization, the B.1.351 virus was poorly neutralized by first wave plasma, with a 15.1-fold drop relative to B.1.351 neutralization by second wave plasma across participants. In contrast, second wave plasma cross-neutralization of the first wave virus was more effective, showing only a 2.3-fold decline relative to first wave plasma neutralization of first wave virus.
These results would seem to suggest that yes, antibodies generated by infection with a variant do protect against other strains and the second-generation vaccines that are being developed based on the B.1.351 should provide greater protection. However, the duration of that protection and protection against future evolving variants is still uncertain. Unlike the speculations made by other virologists, I do not believe Covid-19 will “run out of tricks” and eventually cease to significantly mutate.
To reach this conclusion, we only need to look at the continual evolution of the Influenza virus and the work of evolutionary biologist Jesse Bloom, Ph.D., and his collaborators, who I have written about in past Forbes columns. Bloom has studied cold-causing coronaviruses over a 25 year period and found that although the later serum neutralizes the early virus that doesn’t mean there weren’t further mutations.
Covid-19 is likely to become endemic. The best model we have for protecting ourselves against evolving mutations of the original SARS- CoV-2 strain is how we protect ourselves against Influenza, which will likely mean annual vaccinations along with drug treatments and other public health measures.