Comparative analysis of the risks of hospitalisation and death associated with SARS-CoV-2 omicron (B.1.1.529) and delta (B.1.617.2) variants in England: a cohort study
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Comparative analysis of the risks of hospitalisation and death associated with SARS-CoV-2 omicron (B.1.1.529) and delta (B.1.617.2) variants in England : a cohort study. / Nyberg, Tommy; Ferguson, Neil M.; Nash, Sophie G.; Webster, Harriet H.; Flaxman, Seth; Andrews, Nick; Hinsley, Wes; Bernal, Jamie Lopez; Kall, Meaghan; Bhatt, Samir; Blomquist, Paula; Zaidi, Asad; Volz, Erik; Aziz, Nurin Abdul; Harman, Katie; Funk, Sebastian; Abbott, Sam; Hope, Russell; Charlett, Andre; Chand, Meera; Ghani, Azra C.; Seaman, Shaun R.; Dabrera, Gavin; De Angelis, Daniela; Presanis, Anne M.; Thelwall, Simon; COVID 19 Genom UK COG UK Consortiu.
In: Lancet, Vol. 399, No. 10332, 2022, p. 1303-1312.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Comparative analysis of the risks of hospitalisation and death associated with SARS-CoV-2 omicron (B.1.1.529) and delta (B.1.617.2) variants in England
T2 - a cohort study
AU - Nyberg, Tommy
AU - Ferguson, Neil M.
AU - Nash, Sophie G.
AU - Webster, Harriet H.
AU - Flaxman, Seth
AU - Andrews, Nick
AU - Hinsley, Wes
AU - Bernal, Jamie Lopez
AU - Kall, Meaghan
AU - Bhatt, Samir
AU - Blomquist, Paula
AU - Zaidi, Asad
AU - Volz, Erik
AU - Aziz, Nurin Abdul
AU - Harman, Katie
AU - Funk, Sebastian
AU - Abbott, Sam
AU - Hope, Russell
AU - Charlett, Andre
AU - Chand, Meera
AU - Ghani, Azra C.
AU - Seaman, Shaun R.
AU - Dabrera, Gavin
AU - De Angelis, Daniela
AU - Presanis, Anne M.
AU - Thelwall, Simon
AU - COVID 19 Genom UK COG UK Consortiu
PY - 2022
Y1 - 2022
N2 - Background The omicron variant (B.1.1.529) of SARS-CoV-2 has demonstrated partial vaccine escape and high transmissibility, with early studies indicating lower severity of infection than that of the delta variant (B.1.617.2). We aimed to better characterise omicron severity relative to delta by assessing the relative risk of hospital attendance, hospital admission, or death in a large national cohort.Methods Individual-level data on laboratory-confirmed COVID-19 cases resident in England between Nov 29, 2021, and Jan 9, 2022, were linked to routine datasets on vaccination status, hospital attendance and admission, and mortality. The relative risk of hospital attendance or admission within 14 days, or death within 28 days after confirmed infection, was estimated using proportional hazards regression. Analyses were stratified by test date, 10-year age band, ethnicity, residential region, and vaccination status, and were further adjusted for sex, index of multiple deprivation decile, evidence of a previous infection, and year of age within each age band. A secondary analysis estimated variant-specific and vaccine-specific vaccine effectiveness and the intrinsic relative severity of omicron infection compared with delta (ie, the relative risk in unvaccinated cases).Findings The adjusted hazard ratio (HR) of hospital attendance (not necessarily resulting in admission) with omicron compared with delta was 0.56 (95% CI 0.54-0.58); for hospital admission and death, HR estimates were 0.41 (0.39-0.43) and 0.31 (0.26-0.37), respectively. Omicron versus delta HR estimates varied with age for all endpoints examined. The adjusted HR for hospital admission was 1.10 (0.85-1.42) in those younger than 10 years, decreasing to 0.25 (0.21-0.30) in 60-69-year-olds, and then increasing to 0.47 (0.40-0.56) in those aged at least 80 years. For both variants, past infection gave some protection against death both in vaccinated (HR 0.47 [0.32-0.68]) and unvaccinated (0.18 [0.06-0.57]) cases. In vaccinated cases, past infection offered no additional protection against hospital admission beyond that provided by vaccination (HR 0.96 [0.88-1.04]); however, for unvaccinated cases, past infection gave moderate protection (HR 0.55 [0.48-0.63]). Omicron versus delta HR estimates were lower for hospital admission (0.30 [0.28-0.32]) in unvaccinated cases than the corresponding HR estimated for all cases in the primary analysis. Booster vaccination with an mRNA vaccine was highly protective against hospitalisation and death in omicron cases (HR for hospital admission 8-11 weeks post-booster vs unvaccinated: 0.22 [0.20-0.24]), with the protection afforded after a booster not being affected by the vaccine used for doses 1 and 2.Interpretation The risk of severe outcomes following SARS-CoV-2 infection is substantially lower for omicron than for delta, with higher reductions for more severe endpoints and significant variation with age. Underlying the observed risks is a larger reduction in intrinsic severity (in unvaccinated individuals) counterbalanced by a reduction in vaccine effectiveness. Documented previous SARS-CoV-2 infection offered some protection against hospitalisation and high protection against death in unvaccinated individuals, but only offered additional protection in vaccinated individuals for the death endpoint. Booster vaccination with mRNA vaccines maintains over 70% protection against hospitalisation and death in breakthrough confirmed omicron infections. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd.
AB - Background The omicron variant (B.1.1.529) of SARS-CoV-2 has demonstrated partial vaccine escape and high transmissibility, with early studies indicating lower severity of infection than that of the delta variant (B.1.617.2). We aimed to better characterise omicron severity relative to delta by assessing the relative risk of hospital attendance, hospital admission, or death in a large national cohort.Methods Individual-level data on laboratory-confirmed COVID-19 cases resident in England between Nov 29, 2021, and Jan 9, 2022, were linked to routine datasets on vaccination status, hospital attendance and admission, and mortality. The relative risk of hospital attendance or admission within 14 days, or death within 28 days after confirmed infection, was estimated using proportional hazards regression. Analyses were stratified by test date, 10-year age band, ethnicity, residential region, and vaccination status, and were further adjusted for sex, index of multiple deprivation decile, evidence of a previous infection, and year of age within each age band. A secondary analysis estimated variant-specific and vaccine-specific vaccine effectiveness and the intrinsic relative severity of omicron infection compared with delta (ie, the relative risk in unvaccinated cases).Findings The adjusted hazard ratio (HR) of hospital attendance (not necessarily resulting in admission) with omicron compared with delta was 0.56 (95% CI 0.54-0.58); for hospital admission and death, HR estimates were 0.41 (0.39-0.43) and 0.31 (0.26-0.37), respectively. Omicron versus delta HR estimates varied with age for all endpoints examined. The adjusted HR for hospital admission was 1.10 (0.85-1.42) in those younger than 10 years, decreasing to 0.25 (0.21-0.30) in 60-69-year-olds, and then increasing to 0.47 (0.40-0.56) in those aged at least 80 years. For both variants, past infection gave some protection against death both in vaccinated (HR 0.47 [0.32-0.68]) and unvaccinated (0.18 [0.06-0.57]) cases. In vaccinated cases, past infection offered no additional protection against hospital admission beyond that provided by vaccination (HR 0.96 [0.88-1.04]); however, for unvaccinated cases, past infection gave moderate protection (HR 0.55 [0.48-0.63]). Omicron versus delta HR estimates were lower for hospital admission (0.30 [0.28-0.32]) in unvaccinated cases than the corresponding HR estimated for all cases in the primary analysis. Booster vaccination with an mRNA vaccine was highly protective against hospitalisation and death in omicron cases (HR for hospital admission 8-11 weeks post-booster vs unvaccinated: 0.22 [0.20-0.24]), with the protection afforded after a booster not being affected by the vaccine used for doses 1 and 2.Interpretation The risk of severe outcomes following SARS-CoV-2 infection is substantially lower for omicron than for delta, with higher reductions for more severe endpoints and significant variation with age. Underlying the observed risks is a larger reduction in intrinsic severity (in unvaccinated individuals) counterbalanced by a reduction in vaccine effectiveness. Documented previous SARS-CoV-2 infection offered some protection against hospitalisation and high protection against death in unvaccinated individuals, but only offered additional protection in vaccinated individuals for the death endpoint. Booster vaccination with mRNA vaccines maintains over 70% protection against hospitalisation and death in breakthrough confirmed omicron infections. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd.
U2 - 10.1016/S0140-6736(22)00462-7
DO - 10.1016/S0140-6736(22)00462-7
M3 - Journal article
C2 - 35305296
VL - 399
SP - 1303
EP - 1312
JO - The Lancet
JF - The Lancet
SN - 0140-6736
IS - 10332
ER -
ID: 341842862