20 September 2021

A Swedish study has shown that the alpha variant of SARS-CoV-2 is associated with more severe Covid-19 disease, and leads to more hospital admissions than previous variants.

Photo credit sonreir es gratisRight from the start of the pandemic, it was clear that new variants of the SARS-CoV-2 virus would appear, sooner or later. And we have since then seen how several variants of the virus have spread extensively in some countries.

The first case of infection with the alpha variant in Sweden was confirmed in the final days of December 2020. Researchers from Linköping University, Karolinska Institutet, the National Board of Health and Welfare, and the Public Health Agency of Sweden have now published results from a study of the alpha variant in Sweden.Håkan HanbergerHåkan Hanberger Photo credit John Karlsson

“The study consisted of two different analyses, both of which showed a significantly higher risk for hospital admission and serious disease,” says Håkan Hanberger, professor at Linköping University and consultant in the Infection Clinic at Linköping University Hospital. He is also a member of the Covid-19 analysis group set up by the National Board of Health and Welfare, where he provides clinical expertise.

The study is based on data from three sources: the national Covid-19 registry set up by the National Board of Health and Welfare, typing data for SARS-CoV-2 from a project run by the Public Health Agency of Sweden, and the Swedish Intensive Care Registry. The results have recently been published in Journal of Infection.

“We hope to use the same methods to investigate the risk of needing hospital care and being affected by severe illness when infected by the delta variant, which is now dominant in Sweden”, says Håkan Hanberger.

One of the analyses in the study looked at just over 12,300 people in which the virus variant they were infected with had been determined by genotyping. The researchers looked at differences between individuals who were infected with the alpha variant and those infected by a previous variant of SARS-CoV-2 in Weeks 5-12 in the spring of 2021. Around two-thirds of patients had the alpha variant. The researchers found that infection with the alpha variant was associated with more severe disease and more hospital admissions. The analysis could not, however, investigate the degree of severity of those admitted to hospital, since the group in which the virus had been genotyped was too small.

The other large analysis included more than 324,000 people, where the researchers compared cases of infection with SARS-CoV-2 in Sweden from two different periods of time. The first group was people with confirmed SARS-CoV-2 infection during the period Weeks 45-51 of 2020, which was before the alpha variant had been detected in Sweden. The group was compared with people infected in the period Weeks 12-16 of 2021, when around 9 of 10 of cases in which the variant was identified were the alpha variant. Only people aged 20-69 years without underlying disease or in need of care, and who had not yet been offered vaccination, were included in the study. All confirmed cases that fulfilled the inclusion criteria were included. The researchers showed that the risks of being admitted to hospital, being affected by severe disease, and dying were greater in the group in which the alpha variant dominated. For the patients needing hospital care, there was also an increased risk of being affected by a serious infection, which meant that the need for oxygen gas and/or intensive care was higher.

The article:Impact of the Alpha VOC on disease severity in SARS-CoV-2-positive adults in Sweden”, Kristoffer Strålin, Daniel Bruce, Erik Wahlström, Sten Walther, Moa Rehn, AnnaSara Carnahan, Emmi Andersson, Anna M Bennet Bark, Håkan Hanberger, Journal of Infection, published online on 30 August 2021, https://doi.org/10.1016/j.jinf.2021.08.043

Translated by George Farrants

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