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Abstract

Several SARS-CoV-2 variants that evolved during the COVID-19 pandemic have appeared to differ in severity, based on analyses of single-country datasets. With decreased testing and sequencing, international collaborative studies will become increasingly important for timely assessment of the severity of new variants. Therefore, a joint WHO Regional Office for Europe and ECDC working group was formed to produce and pilot a standardised study protocol to estimate relative case-severity of SARS-CoV-2 variants during periods when two variants were co-circulating. The study protocol and its associated statistical analysis code was applied by investigators in Denmark, England, Luxembourg, Norway, Portugal and Scotland to assess the severity of cases with the Omicron BA.1 virus variant relative to Delta. After pooling estimates using meta-analysis methods (random effects estimates), the risk of hospital admission (adjusted hazard ratio (aHR) = 0.41; 95% confidence interval (CI): 0.31−0.54), admission to intensive care unit (aHR = 0.12; 95% CI: 0.05−0.27) and death (aHR = 0.31; 95% CI: 0.28−0.35) was lower for Omicron BA.1 compared with Delta cases. The aHRs varied by age group and vaccination status. In conclusion, this study demonstrates the feasibility of conducting variant severity analyses in a multinational collaborative framework and adds evidence for the reduced severity of the Omicron BA.1 variant.

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/content/10.2807/1560-7917.ES.2023.28.36.2300048
2023-09-07
2024-11-22
http://instance.metastore.ingenta.com/content/10.2807/1560-7917.ES.2023.28.36.2300048
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A standardised protocol for relative SARS-CoV-2 variant severity assessment, applied to Omicron BA.1 and Delta in six European countries, October 2021 to February 2022
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Tommy+Nyberg&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Nyberg Tommy</a>, <a href="/search?value1=Peter+Bager&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bager Peter</a>, <a href="/search?value1=Ingrid+Bech+Svalgaard&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Svalgaard Ingrid Bech</a>, <a href="/search?value1=Dritan+Bejko&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bejko Dritan</a>, <a href="/search?value1=Nick+Bundle&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bundle Nick</a>, <a href="/search?value1=Josie+Evans&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Evans Josie</a>, <a href="/search?value1=Tyra+Grove+Krause&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Krause Tyra Grove</a>, <a href="/search?value1=Jim+McMenamin&option1=author&noRedirect=true" class="nonDisambigAuthorLink">McMenamin Jim</a>, <a href="/search?value1=Jo%C3%ABl+Mossong&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Mossong Joël</a>, <a href="/search?value1=Heather+Mutch&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Mutch Heather</a>, <a href="/search?value1=Ajibola+Omokanye&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Omokanye Ajibola</a>, <a href="/search?value1=Andr%C3%A9+Peralta-Santos&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Peralta-Santos André</a>, <a href="/search?value1=Pedro+Pinto-Leite&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Pinto-Leite Pedro</a>, <a href="/search?value1=Jostein+Starrfelt&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Starrfelt Jostein</a>, <a href="/search?value1=Simon+Thelwall&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Thelwall Simon</a>, <a href="/search?value1=Lamprini+Veneti&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Veneti Lamprini</a>, <a href="/search?value1=Robert+Whittaker&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Whittaker Robert</a>, <a href="/search?value1=John+Wood&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Wood John</a>, <a href="/search?value1=Richard+Pebody&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Pebody Richard</a>, <a href="/search?value1=Anne+M+Presanis&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Presanis Anne M</a></span>. A standardised protocol for relative SARS-CoV-2 variant severity assessment, applied to Omicron BA.1 and Delta in six European countries, October 2021 to February 2022. <a href="/content/ecdc">Euro Surveill.</a> 2023;28(36):pii=2300048. <a href="https://doi.org/10.2807/1560-7917.ES.2023.28.36.2300048" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2023.28.36.2300048</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 19 Jan 2023;&nbsp;&nbsp; <span class="generated">Accepted</span>: 21 May 2023 </span> </p>
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