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- Title
Household transmission of SARS-CoV-2 Omicron variant of concern subvariants BA.1 and BA.2 in Denmark.
- Authors
Lyngse, Frederik Plesner; Kirkeby, Carsten Thure; Denwood, Matthew; Christiansen, Lasse Engbo; Mølbak, Kåre; Møller, Camilla Holten; Skov, Robert Leo; Krause, Tyra Grove; Rasmussen, Morten; Sieber, Raphael Niklaus; Johannesen, Thor Bech; Lillebaek, Troels; Fonager, Jannik; Fomsgaard, Anders; Møller, Frederik Trier; Stegger, Marc; Overvad, Maria; Spiess, Katja; Mortensen, Laust Hvas
- Abstract
SARS coronavirus 2 (SARS-CoV-2) continues to evolve and new variants emerge. Using nationwide Danish data, we estimate the transmission dynamics of SARS-CoV-2 Omicron subvariants BA.1 and BA.2 within households. Among 22,678 primary cases, we identified 17,319 secondary infections among 50,588 household contacts during a 1–7 day follow-up. The secondary attack rate (SAR) was 29% and 39% in households infected with Omicron BA.1 and BA.2, respectively. BA.2 was associated with increased susceptibility of infection for unvaccinated household contacts (Odds Ratio (OR) 1.99; 95%–CI 1.72-2.31), fully vaccinated contacts (OR 2.26; 95%–CI 1.95–2.62) and booster-vaccinated contacts (OR 2.65; 95%–CI 2.29–3.08), compared to BA.1. We also found increased infectiousness from unvaccinated primary cases infected with BA.2 compared to BA.1 (OR 2.47; 95%–CI 2.15–2.84), but not for fully vaccinated (OR 0.66; 95%–CI 0.57–0.78) or booster-vaccinated primary cases (OR 0.69; 95%–CI 0.59–0.82). Omicron BA.2 is inherently more transmissible than BA.1. Its immune-evasive properties also reduce the protective effect of vaccination against infection, but do not increase infectiousness of breakthrough infections from vaccinated individuals. In this study, the authors use household data from Denmark to investigate the transmissibility of the BA.1 and BA.2 Omicron SARS-CoV-2 subvariants. They find that the secondary attack rate was higher for BA.2, but that it had higher infectiousness only when cases were not vaccinated.
- Subjects
DENMARK; SARS-CoV-2 Omicron variant; SARS-CoV-2; COVID-19; VACCINATION status; BREAKTHROUGH infections; HOUSEHOLDS
- Publication
Nature Communications, 2022, Vol 13, Issue 1, p1
- ISSN
2041-1723
- Publication type
Article
- DOI
10.1038/s41467-022-33498-0