By Alexis Palmer-Fluevog
Researchers from Public Health England looked at the vaccine effectiveness of the Pfizer-BioNTech and Oxford AstraZeneca vaccines against the COVID-19 variants originating in the UK and India. In this pre-print publication that has not yet been peer reviewed, the researchers suggest that two doses of the vaccines should be administered as soon as possible to obtain the greatest effect. This has important implications for the timing of vaccine rollout worldwide.
Take home message:
- Both the Pfizer-BioNTech and Oxford AstraZeneca vaccines can protect against the variants first described in the UK and India, but protection is better after two doses.
As the SARS-CoV-2 variant first described in India (B.1.617.2) continues to spread across the globe leaving devastation in its wake, it is crucial to understand how the currently available vaccines perform against it. In this article, Lopez Bernal and colleagues from Public Health England sought to better understand the effectiveness of the Pfizer-BioNTech and Oxford AstraZeneca vaccines against this variant.
The authors gathered information regarding COVID-19 testing results for all vaccinated people in England. Positive PCR tests between October 2020 and May 2021 were extracted for analysis. To identify the variants, whole genome sequencing was carried out through a network of government-affiliated labs. Data on all symptomatic sequenced cases of COVID-19 in England were used to estimate the proportion of cases with B.1.617.2 compared to the predominant strain in the UK, variant B.1.1.7, by vaccination status.
Of the 12,675 samples tested, 91% were the B.1.1.7 variant and 9% were the B.1.617.2 variant. A single dose of Pfizer or AstraZeneca was only 33% effective in protecting against infection with the variant first detected in India and 51% effective against the variant first detected in the UK. However, an improved effect in both vaccines was noted after two doses. Two weeks after the second dose, the Pfizer vaccine was 93% effective against infection with the B.1.1.7 variant and 88% effective against the B.1.617.2 variant. AstraZeneca’s vaccine was effective, but less so: it was 66% effective against infection with the B.1.1.7 variant and 60% effective against the B.1.617.2 variant.
Most people who were infected after receiving two doses of either the Pfizer or AstraZeneca vaccines had mild symptoms or were asymptomatic. Both the Pfizer and AstraZeneca vaccines showed promising levels of protection against symptomatic COVID-19 disease following two doses.
This analysis showed a lesser effectiveness after one dose highlighting the importance of people following through with two doses of the vaccines as instructed by the manufacturers.
Bernal JL, Andrews N, Gower C, Gallagher E, Simmons R, Thelwall S, Stowe J, Tessier E, Groves N, Dabrera G, Myers R, Campbell C, Amirthalingam G, Edmunds M, Zambon M, Brown K, Hopkins S, Chand M, Ramsay M. medRxiv. 2021 May 24. Effectiveness of COVID-19 vaccines against the B.1.617.2 variant. doi: 10.1101/2021.05.22.21257658.