{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,30]],"date-time":"2026-06-30T18:53:27Z","timestamp":1782845607826,"version":"3.54.5"},"reference-count":32,"publisher":"JMIR Publications Inc.","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JMIR Public Health Surveill"],"abstract":"\n Background<\/jats:title>\n COVID-19 vaccination is crucial in combating the COVID-19 pandemic. Messenger RNA COVID-19 vaccines were initially authorized as a 2-dose primary series and have been widely used in the United States; completing the 2-dose primary series offers protection against infection, severe illness, and death. Understanding the risk factors for not completing the 2-dose primary series is critical to evaluate COVID-19 vaccination programs and promote completion of the 2-dose primary series.<\/jats:p>\n <\/jats:sec>\n \n Objective<\/jats:title>\n This study examined potential risk factors for not completing a 2-dose primary series of mRNA COVID-19 vaccination.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n We conducted a retrospective cohort study among members aged \u226518 years from a large integrated health care system, Kaiser Permanente Southern California, from December 14, 2020, to June 30, 2022. Noncompletion of the 2-dose primary series was defined as not completing the second dose within 6 months after receipt of the first dose. Crude noncompletion rates were estimated overall and by demographic characteristics, health care use patterns, comorbidity, and community-level socioeconomic factors. A Poisson regression model was fit to examine associations of individual-level and community-level risk factors with noncompletion of the 2-dose primary series.<\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n Among 2.5 million recipients of \u22651 dose of mRNA COVID-19 vaccines, 3.3% (n=81,202) did not complete the second dose within 6 months. Members aged 25-44 years, 65-74 years, and \u226575 years were less likely to not complete the 2-dose primary series than those aged 18-24 years, while members aged 45-64 years were more likely to not complete the 2-dose primary series (adjusted risk ratio [aRR] 1.13, 95% CI 1.10-1.15). Male sex was associated with a higher risk of noncompletion (aRR 1.17, 95% CI 1.15-1.19). Hispanic and non-Hispanic Black race\/ethnicity were associated with a lower risk of noncompletion (range aRR 0.78-0.91). Having Medicaid and prior influenza vaccination were associated with a higher risk of noncompletion. Having SARS-CoV-2 infection, experiencing an adverse event, or having an inpatient and emergency department visit during the minimum recommended dose intervals were associated with a higher risk of not completing the 2-dose primary series (aRR 1.98, 95% CI 1.85-2.12; 1.99, 95% CI 1.43-2.76; and 1.85, 95% CI 1.77-1.93, respectively). Those who received the first dose after June 30, 2021, were more likely to not complete the 2-dose primary series within 6 months of receipt of the first dose.<\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n Despite limitations such as being a single-site study and the inability to consider social factors such as employment and vaccine attitudes, our study identified several risk factors for not completing a 2-dose primary series of mRNA vaccination, including being male; having Medicaid coverage; and experiencing SARS-CoV-2 infection, adverse events, or inpatient and emergency department visits during the minimum recommended dose intervals. These findings can inform future efforts in developing effective strategies to enhance vaccination coverage and improve the completion rate of necessary doses.<\/jats:p>\n <\/jats:sec>","DOI":"10.2196\/46318","type":"journal-article","created":{"date-parts":[[2023,8,29]],"date-time":"2023-08-29T00:15:11Z","timestamp":1693268111000},"page":"e46318","source":"Crossref","is-referenced-by-count":1,"title":["Risk Factors for Not Completing a 2-Dose Primary Series of Messenger RNA COVID-19 Vaccination in a Large Health Care System in Southern California: Retrospective Cohort Study"],"prefix":"10.2196","volume":"9","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4750-7672","authenticated-orcid":false,"given":"Stanley","family":"Xu","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6060-8419","authenticated-orcid":false,"given":"Vennis","family":"Hong","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2762-9266","authenticated-orcid":false,"given":"Lina S","family":"Sy","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8277-2431","authenticated-orcid":false,"given":"Katia J","family":"Bruxvoort","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1483-2791","authenticated-orcid":false,"given":"Bruno","family":"Lewin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-0514-7745","authenticated-orcid":false,"given":"Bing","family":"Han","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-1639-9414","authenticated-orcid":false,"given":"Kimberly J","family":"Holmquist","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8001-3992","authenticated-orcid":false,"given":"Lei","family":"Qian","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1010","published-online":{"date-parts":[[2023,10,4]]},"reference":[{"key":"ref1","unstructured":"COVID-19 vaccinations in the United StatesCenters for Disease Control and Prevention20222022-12-11https:\/\/covid.cdc.gov\/covid-data-tracker\/#vaccinations_vacc-total-admin-rate-total"},{"key":"ref2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2034577"},{"key":"ref3","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2035389"},{"key":"ref4","doi-asserted-by":"publisher","DOI":"10.1017\/S0950268822001418"},{"key":"ref5","doi-asserted-by":"publisher","DOI":"10.2196\/35054"},{"key":"ref6","doi-asserted-by":"publisher","DOI":"10.2196\/26874"},{"key":"ref7","doi-asserted-by":"publisher","DOI":"10.1080\/13548506.2022.2084123"},{"key":"ref8","doi-asserted-by":"publisher","DOI":"10.2196\/34163"},{"key":"ref9","doi-asserted-by":"publisher","DOI":"10.1016\/j.pmedr.2023.102200"},{"key":"ref10","doi-asserted-by":"publisher","DOI":"10.2196\/38404"},{"key":"ref11","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-023-35974-z"},{"key":"ref12","doi-asserted-by":"publisher","DOI":"10.1001\/jama.2021.1375"},{"key":"ref13","doi-asserted-by":"publisher","DOI":"10.2807\/1560-7917.ES.2021.26.39.2100894"},{"key":"ref14","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2114228"},{"key":"ref15","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(21)02183-8"},{"key":"ref16","doi-asserted-by":"publisher","DOI":"10.1016\/j.lana.2021.100134"},{"key":"ref17","doi-asserted-by":"publisher","DOI":"10.1038\/s41591-022-01753-y"},{"key":"ref18","doi-asserted-by":"publisher","DOI":"10.1016\/j.vaccine.2022.06.047"},{"key":"ref19","doi-asserted-by":"publisher","DOI":"10.15585\/mmwr.mm7145a2"},{"key":"ref20","doi-asserted-by":"publisher","DOI":"10.2105\/AJPH.2008.151332"},{"key":"ref21","doi-asserted-by":"publisher","DOI":"10.1001\/jamanetworkopen.2020.27577"},{"key":"ref22","doi-asserted-by":"publisher","DOI":"10.1080\/21645515.2021.1879579"},{"key":"ref23","doi-asserted-by":"publisher","DOI":"10.1016\/j.vaccine.2020.12.076"},{"key":"ref24","doi-asserted-by":"publisher","DOI":"10.1016\/j.ajic.2022.05.024"},{"key":"ref25","unstructured":"Source of the Data and Accuracy of the Estimates for the Household Pulse Survey \u2013 Phase 3.3US Census Bureau20222022-12-20https:\/\/www2.census.gov\/programs-surveys\/demo\/technical-documentation\/hhp\/Phase3-3_Source_and_Accuracy_Week41.pdf"},{"key":"ref26","doi-asserted-by":"publisher","DOI":"10.7812\/TPP\/12-031"},{"key":"ref27","unstructured":"Use of COVID-19 vaccines in the United StatesCenters for Disease Control and Prevention20212022-12-29https:\/\/www.cdc.gov\/vaccines\/covid-19\/clinical-considerations\/covid-19-vaccines-us.html"},{"key":"ref28","unstructured":"Interim clinical considerations for use of COVID-19 vaccines in the United StatesCenters for Disease Control and Prevention20232023-01-12https:\/\/www.cdc.gov\/vaccines\/covid-19\/clinical-considerations\/interim-considerations-us.html#timing-spacing-interchangeability"},{"key":"ref29","doi-asserted-by":"publisher","DOI":"10.1016\/j.vaccine.2022.04.037"},{"key":"ref30","doi-asserted-by":"publisher","DOI":"10.7812\/TPP\/22.097"},{"key":"ref31","unstructured":"CocciaMCOVID-19 vaccination is not a sufficient public policy to face crisis management of next pandemic threatsPublic Organization Review20222023-09-12https:\/\/link.springer.com\/article\/10.1007\/s11115-022-00661-6"},{"key":"ref32","doi-asserted-by":"publisher","DOI":"10.1016\/j.envres.2021.112314"}],"container-title":["JMIR Public Health and Surveillance"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/publichealth.jmir.org\/2023\/1\/e46318","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,30]],"date-time":"2026-06-30T17:52:44Z","timestamp":1782841964000},"score":1,"resource":{"primary":{"URL":"https:\/\/publichealth.jmir.org\/2023\/1\/e46318"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,10,4]]},"references-count":32,"URL":"https:\/\/doi.org\/10.2196\/46318","relation":{"has-preprint":[{"id-type":"doi","id":"10.2196\/preprints.46318","asserted-by":"object"}]},"ISSN":["2369-2960"],"issn-type":[{"value":"2369-2960","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,10,4]]}}}