Severity of omicron variant of concern and effectiveness of vaccine boosters against symptomatic disease in Scotland (EAVE II): a national cohort study with nested test-negative design - 23/06/22
, Steven Kerr, PhD a, Mark Woolhouse, ProfPhD a, Jim McMenamin, MBChB b, Chris Robertson, ProfPhD b, con behalf of the
EAVE II Collaborators
Summary |
Background |
Since its emergence in November, 2021, in southern Africa, the SARS-CoV-2 omicron variant of concern (VOC) has rapidly spread across the world. We aimed to investigate the severity of omicron and the extent to which booster vaccines are effective in preventing symptomatic infection.
Methods |
In this study, using the Scotland-wide Early Pandemic Evaluation and Enhanced Surveillance of COVID-19 (EAVE II) platform, we did a cohort analysis with a nested test-negative design incident case-control study covering the period Nov 1–Dec 19, 2021, to provide initial estimates of omicron severity and the effectiveness of vaccine boosters against symptomatic disease relative to 25 weeks or more after the second vaccine dose. Primary care data derived from 940 general practices across Scotland were linked to laboratory data and hospital admission data. We compared outcomes between infection with the delta VOC (defined as S-gene positive) and the omicron VOC (defined as S-gene negative). We assessed effectiveness against symptomatic SARS-CoV-2 infection, with infection confirmed through a positive RT-PCR.
Findings |
By Dec 19, 2021, there were 23 840 S-gene-negative cases in Scotland, which were predominantly among those aged 20–39 years (11 732 [49·2%]). The proportion of S-gene-negative cases that were possible reinfections was more than ten times that of S-gene-positive cases (7·6% vs 0·7%; p<0·0001). There were 15 hospital admissions in S-gene-negative individuals, giving an adjusted observed-to-expected admissions ratio of 0·32 (95% CI 0·19–0·52). The booster vaccine dose was associated with a 57% (54–60) reduction in the risk of symptomatic S-gene-negative infection relative to individuals who tested positive 25 weeks or more after the second vaccine dose.
Interpretation |
These early national data suggest that omicron is associated with a two-thirds reduction in the risk of COVID-19 hospitalisation compared with delta. Although offering the greatest protection against delta, the booster dose of vaccination offers substantial additional protection against the risk of symptomatic COVID-19 for omicron compared with 25 weeks or more after the second vaccine dose.
Funding |
Health Data Research UK, National Core Studies, Public Health Scotland, Scottish Government, UK Research and Innovation, and University of Edinburgh.
Le texte complet de cet article est disponible en PDF.Plan
Vol 22 - N° 7
P. 959-966 - juillet 2022 Retour au numéro
Article précédent
- The Empress and the English Doctor
- Talha Burki
- Risk of hospitalisation associated with infection with SARS-CoV-2 omicron variant versus delta variant in Denmark: an observational cohort study
- Peter Bager, Jan Wohlfahrt, Samir Bhatt, Marc Stegger, Rebecca Legarth, Camilla Holten Møller, Robert Leo Skov, Palle Valentiner-Branth, Marianne Voldstedlund, Thea K Fischer, Lone Simonsen, Nikolai Søren Kirkby, Marianne Kragh Thomsen, Katja Spiess, Ellinor Marving, Nicolai Balle Larsen, Troels Lillebaek, Henrik Ullum, Kåre Mølbak, Tyra Grove Krause, the Omicron-Delta study group, Sofie Marie Edslev, Raphael Niklaus Sieber, Anna Cäcilia Ingham, Maria Overvad, Mie Agermose Gram, Frederikke Kristensen Lomholt, Louise Hallundbæk, Caroline Hjorth Espensen, Sophie Gubbels, Marianne Karakis, Karina Lauenborg Møller, Stefan Schytte Olsen, Zitta Barrella Harboe, Caroline Klint Johannesen, Maarten van Wijhe, Jon Gitz Holler, Ram Benny Christian Dessau, Martin Barfred Friis, David Fuglsang-Damgaard, Mette Pinholt, Thomas Vognbjerg Sydenham, John Eugenio Coia, Ea Sofie Marmolin, Anders Fomsgaard, Jannik Fonager, Morten Rasmussen, Arieh Cohen
Bienvenue sur EM-consulte, la référence des professionnels de santé.
L’accès au texte intégral de cet article nécessite un abonnement.
Déjà abonné à cette revue ?