{"doi":"10.1093/cid/ciab1042","title":"Contact-Tracing Outcomes Among Household Contacts of Fully Vaccinated Coronavirus Disease 2019 (COVID-19) Patients: San Francisco, California, 29 January–2 July 2021","abstract":"BACKGROUND: The extent to which vaccinated persons diagnosed with coronavirus disease 2019 (COVID-19) can transmit to other vaccinated and unvaccinated persons is unclear. METHODS: Using data from the San Francisco Department of Public Health, this report describes outcomes of household contact tracing during 29 January-2 July 2021, where fully vaccinated patients with COVID-19 were the index case in the household. RESULTS: Among 248 fully vaccinated patients with breakthrough infections, 203 (82%) were symptomatic and 105 were identified as the index patient within their household. Among 179 named household contacts, 71 (40%) contacts tested, over half (56%) were fully vaccinated and the secondary attack rate was 28%. Overall transmission from a symptomatic fully vaccinated patient with breakthrough infection to household contacts was suspected in 14 of 105 (13%) of households. Viral genomic sequencing of samples from 44% of fully vaccinated patients showed that 82% of those sequenced were infected by a variant of concern or interest and 77% by a variant carrying mutation(s) associated with resistance to neutralizing antibodies. CONCLUSIONS: Transmission from fully vaccinated symptomatic index patients to vaccinated and unvaccinated household contacts can occur. Indoor face masking and timely testing of all household contacts should be considered when a household member receives a positive test result in order to identify and interrupt transmission chains.","journal":"Clinical Infectious Diseases","year":2021,"id":192538,"datarank":0.6660932983074757,"base_score":2.5649493574615367,"endowment":2.5649493574615367,"self_citation_contribution":0.38474240361923057,"citation_network_contribution":0.28135089468824503,"self_endowment_contribution":0.38474240361923057,"citer_contribution":0.28135089468824503,"corpus_percentile":null,"corpus_rank":null,"citation_count":12,"citer_count":11,"citers_with_citation_signal":8,"citers_with_endowment":8,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.5199,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":760289,"name":"Rilene Chew Ng","orcid":null,"position":1,"is_corresponding":false},{"id":760290,"name":"Madeline Sankaran","orcid":null,"position":2,"is_corresponding":false},{"id":759670,"name":"Alexandra Ernst","orcid":"0000-0002-9154-8316","position":3,"is_corresponding":false},{"id":760291,"name":"Katherine Hernandez","orcid":null,"position":4,"is_corresponding":false},{"id":94466,"name":"Venice Servellita","orcid":"0000-0002-1745-4012","position":5,"is_corresponding":false},{"id":94490,"name":"Alicia Sotomayor-González","orcid":"0000-0002-8930-745X","position":6,"is_corresponding":false},{"id":372815,"name":"Juliet Stoltey","orcid":null,"position":7,"is_corresponding":false},{"id":462119,"name":"Stephanie E. Cohen","orcid":"0000-0002-1632-1074","position":8,"is_corresponding":false},{"id":340106,"name":"Trang Nguyen","orcid":"0000-0002-4730-826X","position":9,"is_corresponding":false},{"id":92394,"name":"Charles Y. Chiu","orcid":"0000-0003-2915-2094","position":10,"is_corresponding":false},{"id":325520,"name":"Susan Philip","orcid":"0000-0002-2325-1916","position":11,"is_corresponding":false},{"id":314411,"name":"Darpun Sachdev","orcid":"0000-0002-7309-8091","position":0,"is_corresponding":true}],"reference_count":19,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-18T23:49:43.496702Z","pmid":"34928340","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}