Nobuhisa Ishiguro

Aim The aim of this study was to determine the risk factors for household transmission of the omicron variant of SARS‐CoV‐2. Background The household infection rate has been reported to be higher for the omicron variant than for non‐omicron variants of SARS‐CoV‐2. Determination of the risk factors for household transmission of the omicron variant is therefore important. Design A Retrospective Cohort Study was conducted. Methods When family members of health care workers (HCWs) were found to be infected with SARS‐CoV‐2, the HCWs had to receive two nucleic acid amplification tests for SARS‐CoV‐2: immediately after and 5 to 10 days after the onset of COVID‐19 in the family members. Risk factors of household transmission were analysed by comparing cases (HCWs infected with SARS‐CoV‐2) and controls (HCWs not infected with SARS‐CoV‐2) using multivariable analysis. Results Unvaccinated status (OR: 3.97), age of index cases (≤6 years) (OR: 1.94) and staying at home with index cases (OR: 10.18) were risk factors for household transmission. Conclusion If there is a strong desire to avoid household infection, family members infected with SARS‐CoV‐2 should live separately during the period of viral shedding.