What do we know about the B.1.617.2 variant?

Scientists are scrambling to understand what role B.1.617.2, the variant first discovered in India, plays in current surges of COVID-19 infections.

The B.1.617.2 variant is one of the factors driving the current crisis in India and Nepal. Phylogenetic testing has shown the B.1.617.2 variant to be also associated with several clusters in Singapore. Researchers also hinted that the variant may be linked to the rising COVID-19 cases among unvaccinated people in the UK.

The B.1.617.2 variant is characterized by spike protein mutations T19R, Δ157-158, L452R, T478K, D614G, P681R, and D950N. [European Centre for Disease Prevention and Control. Threat Assessment Brief: Emergence of SARS-CoV-2 B.1.617 variants in India and situation in the EU/EEA – 11 May 2021: ECDC; 2021]

Several of these mutations may impact on immune responses directed towards the key antigenic regions of receptor binding protein (452 and 478) and deletion of part of the N terminal domain (22). P681R is at the S1/S2 cleavage site and studies have suggested that strains with mutations at that site may have increased replication, leading to higher viral loads and increased transmission. [bioRxiv.2020:2020.08.26.268854]

Are we protected?

The variant is believed to be more contagious than the original SARS-CoV-2 virus, but there’s no clear evidence yet if it causes more severe disease or more deaths. And whether vaccinated groups are truly protected against the B.1.617.2 variant remains to be further validated.

The good news is a recent study showed that two doses of either the Pfizer-BioNTech or AstraZeneca-University of Oxford vaccine gave effective protection against the B.1.617.2 variant. [https://khub.net/documents/135939561/430986542/Effectiveness+of+COVID-19+vaccines+against+the+B.1.617.2+variant.pdf/204c11a4-e02e-11f2-db19-b3664107ac42, accessed 28 May]

Using a test-negative case-control analysis, estimated vaccine effectiveness against symptomatic disease with B.1.617.2 is approximately 33 percent for a single dose of either vaccine, 88 percent for two doses of Pfizer-BioNTech’s BNT162b2, and 60 percent for two doses of AstraZeneca’s ChAdOx1 vaccine.

The findings underscored the need for two doses, as both vaccines were significantly less effective after only one shot.

Additionally, the study has shown that two doses of either vaccine were similarly effective at protecting against the variant that first emerged in the UK. The researchers said these are observational findings that should be interpreted with caution and it is crucial that these are triangulated with emerging in vitro data on immune response in vaccinated individuals.

On top of vaccination, the same stringent public health measures — wearing masks and social distancing — can help prevent the spread of new emerging SARS-CoV-2 variants.