Variants and impact on vaccination against COVID-19

COVID-19 vaccines (both those already developed and those in development) are based on inducing an immune
response to the spicule glycoprotein (S) version of the initial pandemic SARS-CoV-2 virus. The central question being
asked by regulators, vaccine developers, and country health authorities is how much longer the immune response to
this version of S-glycoprotein will continue to be useful against new emerging variants.

The emergence of these variants is due to the very nature of the virus, through point mutations, recombinations,
insertions, or deletions. Several of these variants have put health systems on alert. Notable among these are B.1.1.7,
which emerged in the United Kingdom; B.1.351, which emerged independently in South Africa; and P1, which was
identified as coming from Brazil. These have been accumulating mutations, leading to multiple differences in the
behavior of the virus that can be detected in its transmission dynamics, pathogenicity, and ability to evade antibodies
developed against the initial virus. The B.1.1.7 variant, while it has been associated with a higher mortality rate and
greater transmissibility, has not been shown to affect vaccine efficacy. Variant B.1.351 is associated with a 20%
increase in mortality among hospitalized patients, and there are indications that S-glycoprotein mutations may affect
neutralization by vaccine-generated antibodies, as well as for some monoclonal vaccines, but without loss of vaccine
efficacy. For the P1 variant, it was noted that its transmissibility and antigenic profile have been affected; and with it,
the ability of antibodies generated by previous infections or by vaccination to recognize and neutralize the virus.

The results of clinical studies show that although vaccine efficacy may not be as high in terms of mild or moderate
COVID disease caused by variants, the vaccines are effective in preventing hospitalization and severe COVID.
What is most clear is that as long as protection levels in the population, through vaccination, are not sufficient to
achieve herd immunity, the virus will continue to circulate and spread from person to person, thus incorporating
mutations. Therefore, in addition to the need to continue social distancing, use of masks, and hand washing,
genomic surveillance should continue, identifying variants and assessing their potential impact on vaccination.

Sources:

Rubin R. COVID-19 Vaccines vs. Variants – Determining How Much Immunity is Enough. JAMA. Published online 17
March 2021, doi:10.1001/jama.2021.3370

Darby AC, Hiscox JA. Covid-19: variants and vaccination. BMJ 2021; 372:n771 doi:10.1136/bmj.n771

Link: https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---23-march-2021