Vaccinated COVID-19 Index Cases Are Less Likely to Transmit SARS-CoV-2 to Their Household Contacts: A Cohort Study.

Vaccinated COVID-19 Index Cases Are Less Likely to Transmit SARS-CoV-2 to Their Household Contacts: A Cohort Study.

Publication date: Feb 26, 2024

The aim of this study was to evaluate the impact of index case vaccination on SARS-CoV-2 transmission to household contacts. In our epidemiological cohort study (May 2022-November 2023), we surveyed registered index case vaccination status and test results for contacts (testing on day 0, and on day 7 for negative contacts) and calculated the secondary attack rate (SAR), i. e., newly infected contacts/susceptible included contacts. The association of the independent variable, index case COVID-19 vaccination (yes/no), with household contact infection was determined using the adjusted odds ratio (aOR) and its 95% confidence interval (CI). We recorded 181 index cases and 314 contacts, of whom 250 agreed to participate; 16 contacts were excluded upon testing positive on day 0. Of the 234 included contacts, 49. 1% were women, and the mean (SD) age was 51. 9 (19. 8) years. The overall SAR of 37. 2% (87/234) was lower in the contacts of both vaccinated index cases (34. 9% vs. 63. 2%; p = 0. 014) and index cases with a previous SARS-CoV-2 infection history (27. 0% vs. 46. 3%; p = 0. 002). Index case vaccination showed a protective effect against infection for their household contacts (aOR = 0. 21; 95% CI: 0. 07, 0. 67). The household SAR was high when the Omicron variant circulated. Vaccinated index cases were less likely to transmit SARS-CoV-2 to their contacts.

Open Access PDF

Concepts Keywords
Basel COVID-19
Infection household contact
November incidence rate
Vaccinated SARS-CoV-2
secondary attack rate


Type Source Name
disease VO vaccinated
disease MESH COVID-19
disease VO vaccination
disease MESH infection
pathway REACTOME SARS-CoV-2 Infection
disease IDO history
drug DRUGBANK Coenzyme M
disease MESH Tuberculosis
pathway KEGG Tuberculosis
disease VO vaccine
disease VO effectiveness
disease VO unvaccinated
disease IDO infectivity
disease IDO susceptibility
disease MESH influenza
disease MESH death
disease VO time
disease MESH visual disorders
disease VO organization
disease IDO process
disease MESH secondary infection
disease VO dose
drug DRUGBANK Methionine
disease IDO symptom
disease VO vaccination dose
disease VO USA
drug DRUGBANK Phenindione

Original Article

(Visited 1 times, 1 visits today)