{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T12:44:57Z","timestamp":1777898697551,"version":"3.51.4"},"reference-count":38,"publisher":"SAGE Publications","issue":"6","license":[{"start":{"date-parts":[[2022,8,20]],"date-time":"2022-08-20T00:00:00Z","timestamp":1660953600000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Public Health Rep"],"published-print":{"date-parts":[[2022,11]]},"abstract":"<jats:sec>\n                    <jats:title>Objectives:<\/jats:title>\n                    <jats:p>Information on the effectiveness of COVID-19 contact tracing is lacking. We proposed 2 measures for evaluating the effectiveness of contact tracing and applied them in a public health unit in northern Portugal.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods:<\/jats:title>\n                    <jats:p>This retrospective cohort study included the contacts of people with COVID-19 diagnosed July 1\u2013September 15, 2020. We examined 2 measures: (1) number needed to quarantine (NNQ), as the number of quarantine person-days needed to prevent 1 potential infectious person-day; and (2) proportion of prevented infectious days by quarantine (PPID), as the number of potential infectious days prevented by quarantine divided by all infectious days. We assessed these measures by sociodemographic characteristics, types of contacts, and intervention timings (ie, time between diagnosis or symptom onset and intervention). We considered 3 scenarios for infectiousness periods: 10 days before to 10 days after symptom onset, 3 days before to 3 days after symptom onset, and 2 days before to 10 days after symptom onset.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results:<\/jats:title>\n                    <jats:p>We found an NNQ of 19.8-41.8 person-days and a PPID of 19.7%-38.2%, depending on the infectiousness period scenario. Effectiveness was higher among cohabitants and symptomatic contacts than among social or asymptomatic contacts. NNQ and PPID changed by intervention timings: the effectiveness of contact tracing decreased with time from diagnosis to quarantine of contacts and with time from symptom onset of the index case to contacts\u2019 quarantine.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions:<\/jats:title>\n                    <jats:p>These proposed measures of contact tracing effectiveness of communicable diseases can be important for decision making and prioritizing contact tracing when resources are scarce. They are also useful measures for communication with the general population, policy makers, and clinicians because they are easy to understand and use to assess the impact of health interventions.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1177\/00333549221114343","type":"journal-article","created":{"date-parts":[[2022,8,20]],"date-time":"2022-08-20T07:06:36Z","timestamp":1660979196000},"page":"1178-1186","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":1,"title":["Number Needed to Quarantine and Proportion of Prevented Infectious Days by Quarantine: Evaluating the Effectiveness of COVID-19 Contact Tracing"],"prefix":"10.1177","volume":"137","author":[{"given":"Diogo","family":"Fernandes da Silva","sequence":"first","affiliation":[{"name":"Public Health Unit, Agrupamento de Centros de Sa\u00fade Grande Porto VIII\u2013Espinho\/Gaia, ARS Norte, Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4696-1002","authenticated-orcid":false,"given":"Jo\u00e3o Vasco","family":"Santos","sequence":"additional","affiliation":[{"name":"Public Health Unit, Agrupamento de Centros de Sa\u00fade Grande Porto VIII\u2013Espinho\/Gaia, ARS Norte, Porto, Portugal"},{"name":"Department of Community Medicine, Information and Health Decision Sciences (MEDCIDS), Faculty of Medicine, University of Porto, Porto, Portugal"},{"name":"Centre for Health Technology and Services Research (CINTESIS), Porto, Portugal"}]},{"given":"Filipa","family":"Santos Martins","sequence":"additional","affiliation":[{"name":"Public Health Unit, Agrupamento de Centros de Sa\u00fade Grande Porto VIII\u2013Espinho\/Gaia, ARS Norte, Porto, Portugal"}]}],"member":"179","published-online":{"date-parts":[[2022,8,20]]},"reference":[{"key":"bibr1-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1016\/j.jinf.2020.02.018"},{"key":"bibr2-00333549221114343","doi-asserted-by":"publisher","DOI":"10.3201\/eid1902.120312"},{"key":"bibr3-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1016\/j.jinf.2004.03.002"},{"key":"bibr4-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1016\/B978-012373960-5.00380-4"},{"key":"bibr5-00333549221114343","unstructured":"European Centre for Disease Prevention and Control. Considerations relating to social distancing measures in response to COVID-19\u2014second update. March 23, 2020. Accessed December 16, 2020. https:\/\/www.ecdc.europa.eu\/en\/publications-data\/considerations-relating-social-distancing-measures-response-covid-19-second"},{"key":"bibr6-00333549221114343","doi-asserted-by":"publisher","DOI":"10.2807\/1560-7917.es.2020.25.17.2000257"},{"key":"bibr7-00333549221114343","doi-asserted-by":"publisher","DOI":"10.2807\/1560-7917.es.2020.25.5.2000062"},{"key":"bibr8-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2001316"},{"key":"bibr9-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMc2004973"},{"key":"bibr10-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pone.0000012"},{"key":"bibr11-00333549221114343","unstructured":"European Centre for Disease Prevention and Control. Contact tracing in the European Union: public health management of persons, including healthcare workers, who have had contact with COVID-19 cases in the European Union\u2014fourth update. 2021. Accessed December 16, 2020. https:\/\/www.ecdc.europa.eu\/en\/covid-19-contact-tracing-public-health-management"},{"key":"bibr12-00333549221114343","doi-asserted-by":"publisher","DOI":"10.3389\/fphy.2020.622485"},{"key":"bibr13-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1111\/ijcp.12142"},{"key":"bibr14-00333549221114343","doi-asserted-by":"publisher","DOI":"10.3109\/13697137.2012.656004"},{"key":"bibr15-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1345\/aph.1R417"},{"key":"bibr16-00333549221114343","doi-asserted-by":"publisher","DOI":"10.4088\/JCP.16f11380"},{"key":"bibr17-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1056\/NEJM198806303182605"},{"key":"bibr18-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1016\/j.vaccine.2014.12.033"},{"key":"bibr19-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1016\/j.vaccine.2012.11.097"},{"key":"bibr20-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1542\/peds.2007-0167"},{"key":"bibr21-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1016\/j.vaccine.2003.11.052"},{"key":"bibr22-00333549221114343","unstructured":"Dire\u00e7\u00e3o Geral de Sa\u00fade. Orienta\u00e7\u00e3o 010\/2020: infe\u00e7\u00e3o por SARS CoV 2 (COVID 19)\u2013distanciamento social e isolamento (in Portuguese). Orientation 010\/2020\u2014infection by SARS-CoV-2 (COVID-19)\u2014social distancing and isolation. March 16, 2020. Accessed December 16, 2020. https:\/\/www.dgs.pt\/saude-ocupacional\/documentos-so\/orientacao_10_2020-pdf.aspx"},{"key":"bibr23-00333549221114343","unstructured":"Dire\u00e7\u00e3o Geral de Sa\u00fade. Norma 004\/2020\u2014abordagem das pessoas com suspeita ou confirma\u00e7\u00e3o de COVID-19. In Portuguese. COVID-19: patient approach with suspected or confirmed COVID-19. March 23, 2020. Accessed December 16, 2020. https:\/\/www.dgs.pt\/saude-ocupacional\/documentos-so\/norma_04_2020-pdf.aspx"},{"key":"bibr24-00333549221114343","unstructured":"Dire\u00e7\u00e3o Geral de Sa\u00fade. Norma 015\/2020: rastreio de contactos. In Portuguese. COVID-19: contact tracing. July 24, 2020. Accessed December 16, 2020. https:\/\/www.dgs.pt\/saude-ocupacional\/documentos-so\/norma_15_2020-pdf.aspx"},{"key":"bibr25-00333549221114343","doi-asserted-by":"publisher","DOI":"10.15167\/2421-4248\/jpmh2020.61.3.1530"},{"key":"bibr26-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2008457"},{"key":"bibr27-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1136\/bmjopen-2020-041240"},{"key":"bibr28-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1126\/science.abb6936"},{"key":"bibr29-00333549221114343","doi-asserted-by":"publisher","DOI":"10.3201\/eid2611.203219"},{"key":"bibr30-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1093\/cid\/ciaa1280"},{"key":"bibr31-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1016\/j.cegh.2020.08.007"},{"key":"bibr32-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1101\/2020.04.23.20075796"},{"key":"bibr33-00333549221114343","doi-asserted-by":"publisher","DOI":"10.7326\/M20-0504"},{"key":"bibr34-00333549221114343","doi-asserted-by":"publisher","DOI":"10.2196\/19994"},{"key":"bibr35-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1136\/bmjopen-2020-039652"},{"key":"bibr36-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1017\/S0950268820001338"},{"key":"bibr37-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1101\/2020.10.20.20216143"},{"key":"bibr38-00333549221114343","doi-asserted-by":"publisher","DOI":"10.1016\/j.epidem.2021.100454"}],"container-title":["Public Health Reports\u00ae"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/journals.sagepub.com\/doi\/pdf\/10.1177\/00333549221114343","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.sagepub.com\/doi\/full-xml\/10.1177\/00333549221114343","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.sagepub.com\/doi\/pdf\/10.1177\/00333549221114343","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T09:38:21Z","timestamp":1777628301000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.sagepub.com\/doi\/10.1177\/00333549221114343"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,8,20]]},"references-count":38,"journal-issue":{"issue":"6","published-print":{"date-parts":[[2022,11]]}},"alternative-id":["10.1177\/00333549221114343"],"URL":"https:\/\/doi.org\/10.1177\/00333549221114343","relation":{},"ISSN":["0033-3549","1468-2877"],"issn-type":[{"value":"0033-3549","type":"print"},{"value":"1468-2877","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,8,20]]}}}