01dbe66b4c1159e4ba41edb129057d59 305617.pdf ca8046d1cfe00430c7be0f579276f4ae5dbf2e3a 305617.pdf 13c41832c03ec37d78bf55b8ab61225761551278be173771b67c97e1a8283a1c 305617.pdf Title: Vaccinated COVID-19 Index Cases Are Less Likely to Transmit SARS-CoV-2 to Their Household Contacts: A Cohort Study Subject: 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. Keywords: SARS-CoV-2; COVID-19; incidence rate; vaccine; household contact; secondary attack rate Author: Pere Godoy, Iván Martínez-Baz, Ignasi Parron, Manuel García-Cenoz, Joaquim Ferras, Mònica Carol, Nuria Bes, Montserrat Guillaumes, Sofia Godoy, Diana Toledo, Núria Follia, Carme Miret, Jessica Pardos, Miquel Alsedà, Pedro Plans-Rubio, Inma Sanz, Maria-Rosa Sala, Joan A. Caylà, Jacobo Mendioroz, Carmen Muñoz-Almagro, Jesús Castilla, Ángela Domínguez and on behalf of the SARS-CoV-2 Transmission to Household Contacts Working Group Creator: LaTeX with hyperref Producer: pdfTeX-1.40.25 CreationDate: Mon Feb 26 04:33:56 2024 CET ModDate: Mon Feb 26 04:37:13 2024 CET Custom Metadata: no Metadata Stream: no Tagged: no UserProperties: no Suspects: no Form: none JavaScript: no Pages: 13 Encrypted: no Page size: 595.276 x 841.89 pts (A4) Page rot: 0 File size: 468483 bytes Optimized: no PDF version: 1.7 name type encoding emb sub uni object ID ------------------------------------ ----------------- ---------------- --- --- --- --------- DHPIEQ+VnURWPalladioL-Bold Type 1 Custom yes yes yes 10 0 QPKRGG+URWPalladioL-Bold Type 1 Custom yes yes yes 16 0 UNZCEJ+URWPalladioL-Roma Type 1 Custom yes yes yes 22 0 QBBIOL+URWPalladioL-Ital Type 1 Custom yes yes yes 27 0 OPNYWB+VnURWPalladioL Type 1 Custom yes yes yes 32 0 ZSGSIU+CMSY10 Type 1 Builtin yes yes yes 68 0 CKBPVA+EURM10 Type 1 Builtin yes yes yes 73 0 RIJDHR+CMBSY10 Type 1 Builtin yes yes yes 81 0 MLOEAK+PalatinoLinotype,Bold TrueType WinAnsi yes yes no 96 0 MLOEAL+PalatinoLinotype CID TrueType Identity-H yes yes yes 99 0 MLOEAM+PalatinoLinotype TrueType WinAnsi yes yes no 105 0 MLOEAO+PalatinoLinotype,Italic TrueType WinAnsi yes yes no 108 0 MLOEHO+PalatinoLinotype TrueType MacRoman yes yes no 111 0 MLOFNG+Calibri CID TrueType Identity-H yes yes yes 114 0 WBVKDJ+URWPalladioL-BoldItal Type 1 Custom yes yes yes 123 0 Jhove (Rel. 1.28.0, 2023-05-18) Date: 2025-01-15 02:42:01 CET RepresentationInformation: 305617.pdf ReportingModule: PDF-hul, Rel. 1.12.4 (2023-03-16) LastModified: 2025-01-14 09:18:34 CET Size: 468483 Format: PDF Version: 1.7 Status: Well-Formed and valid SignatureMatches: PDF-hul MIMEtype: application/pdf PDFMetadata: Objects: 314 FreeObjects: 1 IncrementalUpdates: 0 DocumentCatalog: PageLayout: SinglePage PageMode: UseNone Outlines: Item: Title: Introduction Destination: section.1 Item: Title: Materials and Methods Destination: section.2 Children: Item: Title: Study Design Destination: subsection.2.1 Item: Title: Participants Destination: subsection.2.2 Item: Title: Questionnaire Design Destination: subsection.2.3 Item: Title: Data Collection Destination: subsection.2.4 Item: Title: Sampling and Sample Size Destination: subsection.2.5 Item: Title: Statistical Analysis Destination: subsection.2.6 Item: Title: Ethical Considerations Destination: subsection.2.7 Item: Title: Results Destination: section.3 Item: Title: Discussion Destination: section.4 Item: Title: Conclusions Destination: section.5 Item: Title: References Destination: appendix.A. Info: Title: Vaccinated COVID-19 Index Cases Are Less Likely to Transmit SARS-CoV-2 to Their Household Contacts: A Cohort Study Author: Pere Godoy, Iván Martínez-Baz, Ignasi Parron, Manuel García-Cenoz, Joaquim Ferras, Mònica Carol, Nuria Bes, Montserrat Guillaumes, Sofia Godoy, Diana Toledo, Núria Follia, Carme Miret, Jessica Pardos, Miquel Alsedà, Pedro Plans-Rubio, Inma Sanz, Maria-Rosa Sala, Joan A. Caylà, Jacobo Mendioroz, Carmen Muñoz-Almagro, Jesús Castilla, Ángela Domínguez and on behalf of the SARS-CoV-2 Transmission to Household Contacts Working Group Subject: 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. 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