Hospitalisation risk for unjabbed Delta strain sufferers double that of Alpha
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People infected with the Delta variant of Covid-19 who have not been fully vaccinated are twice as likely to require hospital admission as those who tested positive for the previously dominant Alpha strain, a major UK study has found.
The findings from the peer-reviewed research by Public Health England and Cambridge university are particularly concerning for countries with low vaccine coverage as the Delta variant has become the major strain worldwide since July.
“Our analysis highlights that in the absence of vaccination, any Delta outbreaks will impose a greater burden on healthcare than an Alpha epidemic,” said Dr Anne Presanis, a biostatistician at Cambridge university and one of the study’s lead authors.
“Getting fully vaccinated is crucial for reducing an individual’s risk of symptomatic infection . . . and . . . reducing a Delta patient’s risk of severe illness and hospital admission.”
Of the 5.3bn Covid vaccines administered globally, 82 per cent of jabs have been given out in high and upper-middle income countries, while only 0.3 per cent have been distributed in low income countries, according to Our World In Data.
In the PHE/Cambridge study, researchers analysed around 43,000 Covid-19 cases of mainly unvaccinated or partially vaccinated people in England between March and May this year. They found that the Delta strain, which emerged in India, increased the risk of being admitted to hospital by a factor of 2.26, after adjusting for age, underlying health conditions and other factors.
Delta was also associated with a 50 per cent higher risk of an infection resulting in an emergency care visit or hospital admission, according to the study.
The study, published in the Lancet Infectious Diseases journal on Friday, assessed too few fully vaccinated people to draw firm conclusions about the increased risks posed by Delta to them, the researchers said.
According to PHE, Delta is about 60 per cent more contagious than Alpha, and is testing the effectiveness of the vaccines in richer countries with high coverage and triggering fresh waves of infections and hospital admissions across the globe.
Professor Penny Ward, visiting professor in pharmaceutical medicine at King’s College London, said the data was “less concerning for the UK than it may be for countries where vaccine coverage is significantly less”.
She cited New Zealand and Australia, where “new outbreaks of infection caused by the Delta variant take hold in their largely unvaccinated populations.”
The study echoes findings from research looking at nearly 20,000 cases in Scotland published in June. The research team at Edinburgh university found that the Delta variant had an 85 per cent increased risk of hospital admission compared with Alpha.
Peter English, a retired communicable disease control consultant at Public Health England, said the study highlighted the need for further mitigations against Covid-19 in the UK as children return to school and workers to the office in the autumn.
“We know with confidence, that the variant is more virulent — more likely to cause severe illness requiring hospitalisation or emergency care,” he said. “Given that it is this Delta variant that is now prevalent, we should return to a strictly enforced mask mandate in indoor public spaces such as shops, public transport, and consider whether the variant’s increased transmissibility should mean more social distancing and other restrictions, even outdoors.”