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The delta coronavirus variant identified for the first time in India has about twice the risk of hospitalization compared to the alpha variant, which was first identified in Great Britain, according to research published today from Scotland.
While vaccination offers about 70 percent protection against hospitalization, it is important that people get their second dose because protection is limited shortly after the first dose, the authors pointed out.
The Delta variant has become dominant in Scotland since mid-May and now accounts for around 75 percent of all positive cases, said Chris Robertson, Professor of Public Health Epidemiology at the University of Strathclyde, during a briefing. And there are also more younger people among those who are hospitalized.
The latest data came ahead of UK Prime Minister Boris Johnson’s announcement tonight whether pandemic restrictions will be relaxed, with a delay likely to be the case.
“The Delta variant increases the risk of hospitalization,” said Jim McMenamin, COVID-19 National Incident Director for Public Health Scotland. “However, what we can see from the information we have is that our vaccines are still highly effective.”
The BioNTech / Pfizer vaccine offered 79 percent protection against infection by the Delta variant at least two weeks after the second dose, compared with 92 percent against the Alpha variant, the study found.
The Oxford / AstraZeneca vaccine, meanwhile, offered 60 percent protection against the Delta variant compared to 73 percent for the Alpha variant.
The researchers from Edinburgh and Strathclyde Universities and Public Health Scotland said the different rates of effectiveness may reflect the longer it takes to develop immunity with the Oxford / AstraZeneca vaccination. However, they also warned that it was not possible to compare the vaccines directly because they were prioritized for different groups of people.
For both vaccines, the data also showed a “worrying” slightly higher risk of hospitalization with the Delta variant than with Alpha after two doses of the vaccine, noted Robertson.
The results of this analysis, published today as an externally peer-reviewed research letter in the Lancet, were based on community testing of 5.4 million people in Scotland from April 1st to June 6th.
“There is still a lot of work to be done to substantiate the information,” warned McMenamin. “But a full understanding of what these will mean … can only follow if we are able to combine the analyzes carried out in other parts of the UK or internationally.”
Hours after the Scottish data was released, Public Health England published its first analysis of the effectiveness of these two vaccines against the Delta variant with rosier prospects. The Delta variant was previously said to be more transmissible than Alpha and suggested it could cause more hospital admissions, but this review is the first with more complete evidence.
PHE found that the BioNTech / Pfizer vaccine 96 percent prevented hospitalization after two doses, while the Oxford / AstraZeneca vaccine 92 percent prevented hospitalization after two doses.
This was based on the analysis of 14,019 cases of the Delta variant between April 12 and June 4, of which 166 were hospitalized; the Scottish analysis of the Delta variant was drawn from 7,723 cases and 134 hospital admissions.
PHE said the effectiveness of the hospitalization vaccine of the Delta variant was “comparable” to the Alpha variant.
In contrast to the Scottish data, the PHE data focused on preventing serious illness that would require hospitalization. The Scottish analysis of vaccine effectiveness was based on the prevention of all infections in the community, including mild cases.
PHE previously published an analysis showing that one dose is 17 percent less effective in preventing symptomatic disease from the Delta variant compared to Alpha, but there is little difference after two doses, it said.
The results “confirm that the vaccines provide significant protection against hospitalization from the Delta variant,” said Mary Ramsay, director of immunization at PHE. “It is absolutely essential to receive both doses as soon as you offer them to get maximum protection against all existing and emerging variants.”
This story has been updated.