Published: 15 June 2021
Infections from the rising Delta variant of COVID-19 lead to a higher risk of hospital admission than other strains, according to NIHR-funded research.
Data analysed from across Scotland indicated that the Delta variant – first identified in India – has surpassed the Alpha – or Kent – variant to become the dominant form of coronavirus in the country and is twice as likely to lead to hospitalisation.
Despite higher severity and greater transmissibility, the research showed that two vaccine doses still provided strong protection against the Delta strain.
The Early Pandemic Evaluation and Enhanced Surveillance of COVID-19 (EAVE II) project, jointly funded by NIHR and UK Research and Innovation (UKRI), is the first nationwide community study looking at the efficacy of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines.
The research team from the universities of Edinburgh and Strathclyde, as well as Public Health Scotland, uses anonymised linked patient data to track the pandemic and the vaccine rollout in real time.
From 1 April to 6 June, 2021, 19,543 community cases and 377 hospitalisations involving COVID-19 were confirmed out of Scotland’s 5.4m population, with more than a third of cases and hospital admissions linked to the Delta strain.
Vaccines were found to reduce the risk of being admitted to hospital, but it took at least four weeks from the first dose to build significant protection against the newer form.
The study, published in a research letter in The Lancet, showed that in community cases, at least two weeks after a second jab, the Pfizer-BioNTech vaccine provided 79% protection against the Delta variant, compared with 92% against the Alpha variant. The Oxford-AstraZeneca vaccine offered 60% protection against the Delta variant and 73% against the Alpha variant. People with underlying conditions were more at risk of being hospitalised from both variants.
Researchers believe the discrepancy between the vaccines could mean it takes longer to develop immunity with the Oxford-AstraZeneca jab.
Delta variant cases, identifiable by the presence of the coronavirus S gene, were revealed through PCR swab testing results. Alpha variant cases tend to be negative for the S gene.
Professor Aziz Sheikh, Director of the University of Edinburgh’s Usher Institute and EAVE II study lead, said: “Over a matter of weeks the Delta variant has become the dominant strain of SARS-CoV-2 in Scotland. It is unfortunately associated with increased risk of hospitalisation from COVID-19.
“Whilst possibly not as effective as against other variants, two doses of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines still offer substantial protection against the risk of infection and hospitalisation. It is therefore really important that, when offered second doses, people take these up both to protect themselves and to reduce household and community transmission.”