ABSTRACT
BACKGROUND: This study compares the severity of SARS-CoV-2 infections caused by Alpha, Delta or Omicron variants in periods of co-circulation in Spain, and estimates the variant-specific association of vaccination with severe disease. METHODS: SARS-CoV-2 infections notified to the national epidemiological surveillance network with information on genetic variant and vaccination status were considered cases if they required hospitalisation or controls otherwise. Alpha and Delta were compared during June-July 2021; and Delta and Omicron during December 2021-January 2022. Adjusted Odds Ratios (aOR) were estimated using logistic regression, comparing variant and vaccination status between cases and controls. RESULTS: We included 5,345 Alpha and 11,974 Delta infections in June-July and, 5,272 Delta and 10,578 Omicron in December-January. Unvaccinated cases of Alpha (aOR: 0.57; 95% CI: 0.46-0.69) or Omicron (0.28; 0.21-0.36) had lower probability of hospitalisation vs. Delta. Complete vaccination reduced hospitalisation, similarly for Alpha (0.16; 0.13-0.21) and Delta (June-July: 0.16; 0.14-0.19; December-January: 0.36; 0.30-0.44) but lower from Omicron (0.63; 0.53-0.75) and individuals aged 65+ years. CONCLUSION: Results indicate higher intrinsic severity of the Delta variant, compared with Alpha or Omicron, with smaller differences among vaccinated individuals. Nevertheless, vaccination was associated to reduced hospitalisation in all groups.
ABSTRACT
Background This study compares the severity of SARS-CoV-2 infections caused by Alpha, Delta or Omicron variants in periods of co-circulation in Spain, and estimates the variant-specific association of vaccination with severe disease. Methods SARS-CoV-2 infections notified to the national epidemiological surveillance network with information on genetic variant and vaccination status were considered cases if they required hospitalisation or controls otherwise. Alpha and Delta were compared during June–July 2021;and Delta and Omicron during December 2021–January 2022. Adjusted odds ratios (aOR) were estimated using logistic regression, comparing variant and vaccination status between cases and controls. Results We included 5,345 Alpha and 11,974 Delta infections in June–July and 5,272 Delta and 10,578 Omicron in December–January. Unvaccinated cases of Alpha (aOR: 0.57;95% CI: 0.46–0.69) or Omicron (0.28;0.21–0.36) had lower probability of hospitalisation vs. Delta. Complete vaccination reduced hospitalisation, similarly for Alpha (0.16;0.13–0.21) and Delta (June–July: 0.16;0.14–0.19;December–January: 0.36;0.30–0.44) but lower from Omicron (0.63;0.53–0.75) and individuals aged 65+ years. Conclusion Results indicate higher intrinsic severity of the Delta variant, compared with Alpha or Omicron, with smaller differences among vaccinated individuals. Nevertheless, vaccination was associated to reduced hospitalisation in all groups.
ABSTRACT
BACKGROUND: This study compares the severity of SARS-CoV-2 infections caused by Alpha, Delta or Omicron variants in periods of co-circulation in Spain, and estimates the variant-specific association of vaccination with severe disease. METHODS: SARS-CoV-2 infections notified to the national epidemiological surveillance network with information on genetic variant and vaccination status were considered cases if they required hospitalisation or controls otherwise. Alpha and Delta were compared during June-July 2021; and Delta and Omicron during December 2021-January 2022. Adjusted odds ratios (aOR) were estimated using logistic regression, comparing variant and vaccination status between cases and controls. RESULTS: We included 5,345 Alpha and 11,974 Delta infections in June-July and 5,272 Delta and 10,578 Omicron in December-January. Unvaccinated cases of Alpha (aOR: 0.57; 95% CI: 0.46-0.69) or Omicron (0.28; 0.21-0.36) had lower probability of hospitalisation vs. Delta. Complete vaccination reduced hospitalisation, similarly for Alpha (0.16; 0.13-0.21) and Delta (June-July: 0.16; 0.14-0.19; December-January: 0.36; 0.30-0.44) but lower from Omicron (0.63; 0.53-0.75) and individuals aged 65+ years. CONCLUSION: Results indicate higher intrinsic severity of the Delta variant, compared with Alpha or Omicron, with smaller differences among vaccinated individuals. Nevertheless, vaccination was associated to reduced hospitalisation in all groups.
ABSTRACT
Introducción: El objetivo es comprar la gravedad de las infecciones por las variantes Alfa, Delta y Ómicron del SARS-CoV-2 en periodos de co-circulación en España, y estimar la asociación entre vacunación y gravedad en cada variante. Métodos: Las infecciones por SARS-CoV-2 notificadas a la red nacional de vigilancia epidemiológica con información sobre la variante viral y el estado de vacunación se clasificaron como casos si habían requerido hospitalización, o como controles en caso contrario. Alfa y Delta se compararon durante Junio-Julio de 2021;y Delta y Ómicron durante Diciembre 2021-Enero 2022. Se estimaron Odds Ratios ajustadas (ORa) mediante regresión logística, comparando la variante y el estado de vacunación entre casos y controles. Resultados: Se incluyeron 5,345 infecciones por variante Alfa y 11,974 por Delta en Junio-Julio y 5,272 infecciones por Delta y 10,578 por Ómicron en Diciembre-Enero. Los casos no vacunados por Alfa (aOR: 0.57;95% CI: 0.46-0.69) u Ómicron (0.28;0.21-0.36) tuvieron menor probabilidad de hospitalización comparado con Delta. La vacunación completa se asoció a menor hospitalización de forma similar para Alfa (0.16;0.13-0.21) y Delta (Junio-Julio: 0.16;0.14-0.19;Diciembre-Enero: 0.36;0.30-0.44) pero menor para Ómicron (0.63;0.53-0.75) y para individuos con 65+ años. Conclusion: Los resultados indican una mayor gravedad intrínseca de la variante Delta comparada con Alfa u Ómicron, con menor diferencia entre personas vacunadas. La vacunación se asoció a menor hospitalización en todos los grupos.