{Reference Type}: Journal Article
{Title}: Vaccinated COVID-19 Index Cases Are Less Likely to Transmit SARS-CoV-2 to Their Household Contacts: A Cohort Study.
{Author}: Godoy P;Martínez-Baz I;Parron I;García-Cenoz M;Ferras J;Carol M;Bes N;Guillaumes M;Godoy S;Toledo D;Follia N;Miret C;Pardos J;Alsedà M;Plans-Rubio P;Sanz I;Sala MR;Caylà JA;Mendioroz J;Muñoz-Almagro C;Castilla J;Domínguez Á;On Behalf Of The Sars-CoV-Transmission To Household Contacts Working Group ;
{Journal}: Vaccines (Basel)
{Volume}: 12
{Issue}: 3
{Year}: 2024 Feb 26
{Factor}: 4.961
{DOI}: 10.3390/vaccines12030240
{Abstract}: 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.