{"id":23378,"date":"2026-03-07T10:31:34","date_gmt":"2026-03-07T15:31:34","guid":{"rendered":"https:\/\/www.ices.on.ca\/?post_type=journal_article&#038;p=23378"},"modified":"2026-03-11T10:38:16","modified_gmt":"2026-03-11T14:38:16","slug":"examining-the-interaction-between-area-level-immunity-coverage-and-individual-level-immunity-to-help-quantify-indirect-herd-benefits","status":"publish","type":"journal_article","link":"https:\/\/www.ices.on.ca\/fr\/publications\/journal-articles\/examining-the-interaction-between-area-level-immunity-coverage-and-individual-level-immunity-to-help-quantify-indirect-herd-benefits\/","title":{"rendered":"Examining the interaction between area-level immunity coverage and individual-level immunity to help quantify indirect herd benefits: a population-based retrospective cohort study of COVID-19 diagnoses and deaths"},"content":{"rendered":"<p>Empirical evidence on the indirect herd benefits of COVID-19 vaccination and\/or prior infection is limited. We examined how area-level immunity interacts with individual-level immunity to affect COVID-19 diagnoses and deaths. Ontario residents aged \u226518 years were followed from August-01-2021 to January-30-2022. Individual-level immunity was defined as receipt of a primary series of COVID-19 vaccines or a positive SARS-CoV-2 test in the past 165 days. Area-level immunity was based on the proportion of immune individuals in an individual\u2019s residing area. Logistic regression and cause-specific hazard models were used to examine the relationship between immunity and COVID-19 diagnosis, and between immunity and COVID-19 death, with an interaction term between individual-level and area-level immunity. Of 11,122,816 adults, 7,518,015 (67.6%) were classified as having individual-level immunity at baseline. After accounting for potential confounders, area-level immunity (highest vs. lowest quintiles) was associated with lower odds of COVID-19 diagnosis. Higher area-level immunity (highest vs. lowest quintiles) was also associated with lower hazard of COVID-19 death among non-immune individuals (hazard ratio: 0.77 [0.60, 1.00]). Findings provide evidence supporting the herd benefits of vaccination or prior infection on COVID-19 diagnosis and deaths, and provide insights for interpreting vaccine effectiveness estimates in the context of herd immunity.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Empirical evidence on the indirect herd benefits of COVID-19 vaccination and\/or prior infection is limited. We examined how area-level immunity interacts with individual-level immunity to affect COVID-19 diagnoses and deaths. Ontario residents aged \u226518 years were followed from August-01-2021 to January-30-2022. Individual-level immunity was defined as receipt of a primary series of COVID-19 vaccines or [&hellip;]<\/p>\n","protected":false},"template":"","migration-helper-automated":[],"migration-manual":[],"topic":[64,35],"migration-helper-qa-sample-set":[],"class_list":["post-23378","journal_article","type-journal_article","status-publish","hentry","topic-epidemiology","topic-public-health"],"acf":{"citation":"Wang L, Swayze S, Siddiqi A, Baral SD, Sander B, Sbihi H, Kwong JC, Mishra S. <em>Am J Epidemiol<\/em>. 2026; Mar 7 [Epub ahead of print].","source_url":"https:\/\/doi.org\/10.1093\/aje\/kwag047","ices_scientist":[1362,1149,1320],"site":[6733],"research_program":[6741],"news_release":"","journal_article":"","atlas":"","research_report":"","infographic":"","video":"","downloads":null,"links":null,"sitecore_item_id":"","sitecore_item_name":"","sitecore_field_values":"","previous_url":""},"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.1 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>ICES | Examining the interaction between area-level immunity coverage and individual-level immunity to help quantify indirect herd benefits: a population-based retrospective cohort study of COVID-19 diagnoses and deaths<\/title>\n<meta name=\"description\" content=\"Empirical evidence on the indirect herd benefits of COVID-19 vaccination and\/or prior infection is limited. 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