Secondary household transmission of SARS-CoV-2: a case-control study on factors associated with reduced transmission risk.

This study aimed to identify factors deterring secondary household transmission of SARS-CoV-2 from SARS-CoV-2-positive cohabitants. A case-control study was conducted with 272 healthcare workers in close contact with SARS-CoV-2-positive cohabitants. Logistic regression modeling was employed to determine the factors independently associated with secondary household transmission. A SARS-CoV-2 infection within the past 6 months was the most protective factor against secondary household transmission (adjusted odds ratio = 0.07, 95% CI: 0.01-0.61, P <0.05). Home isolation and older age of primary index case (7-12, ≥18 years) were also associated with a reduced risk. Both monovalent and bivalent messenger ribonucleic acid booster vaccinations exhibited potential protective tendencies but were not statistically significant. Additionally, bivalent vaccines did not demonstrate a clear advantage over monovalent vaccines. A recent history of SARS-CoV-2 infection, home isolation of positive cohabitants, and older age of primary index cases were positively associated with a reduced risk of secondary household transmission. Regarding booster vaccinations, data from a single center with a limited sample size may not capture all statistically significant differences, necessitating broader studies.

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Declarations of competing interest The authors have no competing interests to declare.