How well do existing Covid-19 vaccines work against Coronavirus variants? These charts show all you need to know.
Current vaccines were designed to work against the SARS-CoV-2 coronavirus that originated in Wuhan, China. But as the virus evolves around the world, new variants are emerging that seem to evade the human immune system. Several strains are concerning for public health because they’re more transmissible and/or more deadly — notably the Alpha, Beta, Gamma and Delta variants first detected in the UK, South Africa, Brazil and India. People are being given a variety of different vaccines to help trigger immunity, slow the spread of Covid-19 and stop outbreaks. Are existing drugs effective against variants? While there are many ways to measure whether a vaccine is effective, here I’ve focused on a figure most often highlighted in scientific studies: the proportion of people that a drug has protected from developing moderate to severe disease. For preventing Covid, that percentage is usually calculated after accounting for both symptomatic and asymptomatic infections, which produces a real-world figure for a vaccine’s effectiveness. This article covers four available vaccines: ‘ChAdOx1 nCoV-19’/AZD1222 developed by University of Oxford/AstraZeneca and Ad26. COV2. S by Johnson & Johnson/Janssen — which use viral vectors to deliver Coronavirus spike proteins to prompt immune responses — and BNT162b2 by Pfizer/BioNTech and mRNA-1273 by Moderna, two drugs based on mRNA technology that deliver the genes for making spikes. I’ve collected data from a dozen sources: research published in The Lancet and New England Journal of Medicine (NEJM), plus an as-yet unpublished report from Public Health England (PHE) on how well the AstraZeneca and Pfizer vaccines work against the Delta (B.1.617.2) variant. The bar chart above shows each vaccine’s effectiveness or ‘efficacy’ at preventing Covid caused by variants (no data doesn’t mean zero efficacy). All figures are approximate and should be treated as such. That caveat aside, all four vaccines are highly effective against the original virus but less so against each ‘ Variant of Concern ‘ (I didn’t find reliable data on Gamma/P.
