Jul 29, 2021
Variant Of Interest Coming Attraction: B.1.621
Pango lineage B.1.621 (aka 21H in the Nextstrain Clade naming convention) is not yet a Variant of Interest (VOI). My quick peek at its activity on my stalwart variants source, Covariants.org, shows a story in some nations that tells me WHO will name it a VOI soon.
21H is most prevalent in Colombia where it does appear to outcompete Gamma, which is the VOC (Variant of Concern) that has been making things miserable in Brazil. Not clear by how much. Colombia’s sequencing data is so sparse, error bars are large and the observed variant frequencies could be dominated by sampling missteps and founder’s effect (founders effect example: imagine you end up coding a bunch of samples from one town or hospital, and it just so happened that 21H showed up a superspreader gathering). The small numbers of sequences in Colombia are even smaller for the subsequent two periods ending in June and there is zero July data.
What I want to know is how B.1.621 does head-to-head with Delta (B.1.617.2). It has several spike mutations that Delta does not with unknown impact on immune evasion. If it out competes Delta, the immune evasion could be problematic. So far infection/vaccination with ANY variant does seem to reduce susceptibility (this changes the fraction of people able to get infected and how well something can spread) to other variants at least some, so it is unclear just how “problematic” any possible immune evasion might be. It looks to me like we will learn this in Mexico, Ecuador or Florida over the coming weeks.
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Mexico most likely will be the place to watch because Mexico has a sizeable Delta fraction AND some statistically significant B.1.621 numbers. I am assuming they are trying to randomly select which samples they sequence.
Florida has more Delta than Mexico but B.1.621 is just getting a toehold there so it will take a while to be clear if it is winning out, showing up in a larger and larger fraction of cases. The University of Miami is recently seeing a larger fraction of B.1.621* but they may be sequencing samples from one hospital and I don’t know if the statistical significance of 10%: it could mean 5 sequences or 500.
If B.1.621 can’t outcompete Delta. any possible immune evasion won’t matter. In a month it will be clear if this soon to be named VOI is something that might become a problem.
( I continue to assest Lambda will vanish under Delta and others.)
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- My goodness, what a mouthful. I think I am going to switch to the NextStrain convention in future 21H. Much easier.
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