{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T09:54:41Z","timestamp":1787738081625,"version":"build-2784847793"},"reference-count":30,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T00:00:00Z","timestamp":1760227200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"id.DRIVE"},{"name":"AstraZeneca"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background\/Objectives: Precautionary health behaviours (PHBs), such as hand-washing or self-isolation, are non-pharmaceutical interventions used to reduce SARS-CoV-2 transmission. We investigated the potential confounding by PHBs of COVID-19 vaccine effectiveness (VE) estimates in a subset of study participants enrolled in id.DRIVE. Methods: The id.DRIVE COVID-19 VE study (formerly COVIDRIVE) is a European multicentre test-negative case\u2013control study estimating COVID-19 VE against hospitalisation due to laboratory-confirmed SARS-CoV-2 in patients with severe acute respiratory infection. All adults (\u226518 y) prospectively enrolled between 16 November 2021 and 16 August 2023 at three sites were invited to complete a PHB survey capturing indicators of PHBs in the 3 months preceding admission. Fisher\u2019s exact test with Bonferroni-adjusted threshold was used to measure the level of association between PHB indicators and both COVID-19 vaccine status and SARS-CoV-2 test result. VE estimates were generated with and without adjustment for PHBs. Results: PHBs were modified over time, with higher precautionary attitudes in the first COVID-19 vaccine booster season (2021\u20132022) compared to the second one (2022\u20132023). For the first booster season, PHBs were positively associated with exposures (vaccination status) and outcomes (case or control status). Adjusting for PHBs led to a 6 to 9 percentage-point increase in VE estimates. Conversely, no confounding by PHBs was observed in the second booster season. Conclusions: PHBs should be considered a possible confounder of COVID-19 VE studies. Further research is needed to define when PHBs should be integrated into VE models, as the level of confounding may differ according to the study population and the epidemiological context.<\/jats:p>","DOI":"10.3390\/vaccines13101047","type":"journal-article","created":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T08:10:31Z","timestamp":1760343031000},"page":"1047","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Precautionary Health Behaviours as Potential Confounders in COVID-19 Vaccine Effectiveness Studies"],"prefix":"10.3390","volume":"13","author":[{"given":"Chlo\u00e9","family":"Wyndham-Thomas","sequence":"first","affiliation":[{"name":"P95 Clinical and Epidemiology Services, Diestsevest 125, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6573-2032","authenticated-orcid":false,"given":"Leonie","family":"de Munter","sequence":"additional","affiliation":[{"name":"P95 Clinical and Epidemiology Services, Weena 690, 3012 CN Rotterdam, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kok Yew","family":"Ngew","sequence":"additional","affiliation":[{"name":"P95 Clinical and Epidemiology Services, Diestsevest 125, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sanskruti","family":"Gaikwad","sequence":"additional","affiliation":[{"name":"P95 Clinical and Epidemiology Services, Weena 690, 3012 CN Rotterdam, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9167-8201","authenticated-orcid":false,"given":"Konstantina","family":"Chatzikonstantinidou","sequence":"additional","affiliation":[{"name":"P95 Clinical and Epidemiology Services, Diestsevest 125, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Antonio","family":"Carmona","sequence":"additional","affiliation":[{"name":"Fundaci\u00f3n Fomento de la Investigaci\u00f3n Sanitaria y Biom\u00e9dica de la Comunidad Valenciana, Av. de Catalunya 21, 46020 Valencia, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8995-6230","authenticated-orcid":false,"given":"Charlotte","family":"Martin","sequence":"additional","affiliation":[{"name":"Centre Hospitalier Universitaire St Pierre, Rue Haute 322, 1000 Brussels, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7043-8046","authenticated-orcid":false,"given":"Gerrit Luit","family":"ten Kate","sequence":"additional","affiliation":[{"name":"Universitair Ziekenhuis Antwerpen, Drie Eikenstraat 655, 2650 Edegem, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nicolas","family":"Praet","sequence":"additional","affiliation":[{"name":"Janssen Research & Development, LLC, 2340, Turnhoutseweg 30, 2340 Beerse, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wilhelmine","family":"Meeraus","sequence":"additional","affiliation":[{"name":"Medical Evidence, Vaccines & Immune Therapies, AstraZeneca, Cambridge CB2 8DU, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-2509-1098","authenticated-orcid":false,"given":"Matthew D.","family":"Rousculp","sequence":"additional","affiliation":[{"name":"Novavax, Inc., Gaithersburg, MD 20878, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kaatje","family":"Bollaerts","sequence":"additional","affiliation":[{"name":"P95 Clinical and Epidemiology Services, Diestsevest 125, 3000 Leuven, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"714","DOI":"10.1016\/S2213-2600(24)00179-6","article-title":"Estimated number of lives directly saved by COVID-19 vaccination programmes in the WHO European Region from December, 2020, to March, 2023: A retrospective surveillance study","volume":"12","author":"Brown","year":"2024","journal-title":"Lancet Respir. Med."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.physrep.2021.02.001","article-title":"Non-pharmaceutical interventions during the COVID-19 pandemic: A review","volume":"913","author":"Perra","year":"2021","journal-title":"Phys. Rep."},{"key":"ref_3","unstructured":"European Centre for Disease Prevention and Control (2024, March 28). Public Health Control Measures for COVID-19. Available online: https:\/\/www.ecdc.europa.eu\/en\/publications-data\/public-health-and-social-measures-health-emergencies-and-pandemics."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"480","DOI":"10.1093\/tbm\/ibab150","article-title":"Relationship between mask wearing, testing, and vaccine willingness among Los Angeles County adults during the peak of the COVID-19 pandemic","volume":"12","author":"Lam","year":"2022","journal-title":"Transl. Behav. Med."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e068302","DOI":"10.1136\/bmj-2021-068302","article-title":"Effectiveness of public health measures in reducing the incidence of COVID-19, SARS-CoV-2 transmission, and COVID-19 mortality: Systematic review and meta-analysis","volume":"375","author":"Talic","year":"2021","journal-title":"BMJ"},{"key":"ref_6","unstructured":"European Centre for Disease Prevention and Control (2024, March 28). Core Protocol for ECDC Studies of COVID-19 Vaccine Effectiveness Against Hospitalisation with Severe Acute Respiratory Infection, laboratory-Confirmed with SARS-CoV-2 or with Seasonal Influenza\u2014Version 3.0. Available online: https:\/\/www.ecdc.europa.eu\/en\/publications-data\/core-protocol-ecdc-studies-covid-19-vaccine-effectiveness-3."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"100675","DOI":"10.1016\/j.lanepe.2023.100675","article-title":"Protection against COVID-19 hospitalisation conferred by primary-series vaccination with AZD1222 in non-boosted individuals: First vaccine effectiveness results of the European COVIDRIVE study and meta-regression analysis","volume":"31","author":"Meeraus","year":"2023","journal-title":"Lancet Reg. Health Eur."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Iorfa, S.K., Ottu, I.F.A., Oguntayo, R., Ayandele, O., Kolawole, S.O., Gandi, J.C., Dangiwa, A.L., and Olapegba, P.O. (2020). COVID-19 Knowledge, Risk Perception, and Precautionary Behavior Among Nigerians: A Moderated Mediation Approach. Front. Psychol., 11.","DOI":"10.3389\/fpsyg.2020.566773"},{"key":"ref_9","unstructured":"UK Health Security Agency (2024, October 23). COVID-19 Vaccine Surveillance Report\u2014Week 29, Available online: https:\/\/assets.publishing.service.gov.uk\/media\/669923b20808eaf43b50d1fd\/Vaccine_surveillance_report_2024_week_29.pdf."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Hahn\u00e9, S., Bollaerts, K., and Farrington, P. (2022). Estimating Vaccine Effectiveness: Case-Control and Screening Studies. Vaccination Programmes: Epidemiology, Monitoring, Evaluation, Routledge.","DOI":"10.4324\/9781315166414"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"285","DOI":"10.1038\/s41597-020-00609-9","article-title":"A structured open dataset of government interventions in response to COVID-19","volume":"7","author":"Dervic","year":"2020","journal-title":"Sci. Data"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"837","DOI":"10.1007\/s10433-021-00636-4","article-title":"Time patterns of precautionary health behaviours during an easing phase of the COVID-19 pandemic in Europe","volume":"19","author":"Branyiczki","year":"2022","journal-title":"Eur. J. Ageing"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"202194","DOI":"10.1016\/j.jeph.2024.202194","article-title":"Factors associated with compliance with barrier gestures and social distancing measures in France","volume":"72","author":"Metzger","year":"2024","journal-title":"J. Epidemiol. Popul. Health"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"AlAmodi, A.A., Al-Kattan, K., and Shareef, M.A. (2021). The current global perspective of the knowledge-attitude-behavior of the general public towards the corona virus disease-19 pandemic: Systematic review and meta-analysis on 67,143 participants. PLoS ONE, 16.","DOI":"10.1371\/journal.pone.0260240"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Wambua, J., Loedy, N., Jarvis, C.I., Wong, K.L.M., Faes, C., Grah, R., Prasse, B., Sandmann, F., Niehus, R., and Johnson, H. (2023). The influence of COVID-19 risk perception and vaccination status on the number of social contacts across Europe: Insights from the CoMix study. BMC Public Health, 23.","DOI":"10.1186\/s12889-023-16252-z"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"100012","DOI":"10.1016\/j.lanepe.2020.100012","article-title":"Attitudes towards vaccines and intention to vaccinate against COVID-19: Implications for public health communications","volume":"1","author":"Paul","year":"2021","journal-title":"Lancet Reg. Health Eur."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"3984","DOI":"10.1038\/s41467-023-39674-0","article-title":"Bias assessment of a test-negative design study of COVID-19 vaccine effectiveness used in national policymaking","volume":"14","author":"Graham","year":"2023","journal-title":"Nat. Commun."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"5105","DOI":"10.1080\/21645515.2021.1978794","article-title":"Vaccination induced complacency in adherence to COVID-19 precautionary measures among oral health care professionals in India and the United States: A retrospective pretest-posttest design","volume":"17","author":"Chandu","year":"2021","journal-title":"Hum. Vaccines Immunother."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Yang, L.X., Lin, C.Y., Zhan, W.Z., Chiang, B.A., and Chang, E.C. (2024). Why Do We Not Wear Masks Anymore during the COVID-19 Wave? Vaccination Precludes the Adoption of Personal Non-Pharmaceutical Interventions: A Quantitative Study of Taiwanese Residents. Medicina, 60.","DOI":"10.3390\/medicina60020301"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Zsichla, L., and M\u00fcller, V. (2023). Risk Factors of Severe COVID-19: A Review of Host, Viral and Environmental Factors. Viruses, 15.","DOI":"10.3390\/v15010175"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"344","DOI":"10.1093\/infdis\/jiac411","article-title":"Alpha to Omicron: Disease Severity and Clinical Outcomes of Major SARS-CoV-2 Variants","volume":"227","author":"Esper","year":"2023","journal-title":"J. Infect. Dis."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1818","DOI":"10.1056\/NEJMc2302462","article-title":"Durability of Bivalent Boosters against Omicron Subvariants","volume":"388","author":"Lin","year":"2023","journal-title":"N. Engl. J. Med."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"528","DOI":"10.1038\/s41579-021-00535-6","article-title":"Transmissibility and transmission of respiratory viruses","volume":"19","author":"Leung","year":"2021","journal-title":"Nat. Rev. Microbiol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1016\/S1473-3099(22)00525-4","article-title":"Epidemiology of respiratory syncytial virus in children younger than 5 years in England during the COVID-19 pandemic, measured by laboratory, clinical, and syndromic surveillance: A retrospective observational study","volume":"23","author":"Bardsley","year":"2023","journal-title":"Lancet Infect. Dis."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/S1473-3099(22)00544-8","article-title":"Quantifying the RSV immunity debt following COVID-19: A public health matter","volume":"23","author":"Billard","year":"2023","journal-title":"Lancet Infect. Dis."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1002","DOI":"10.1016\/j.ijid.2022.08.002","article-title":"Understanding the rebound of influenza in the post COVID-19 pandemic period holds important clues for epidemiology and control","volume":"122","author":"Lee","year":"2022","journal-title":"Int. J. Infect. Dis."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"e13087","DOI":"10.1111\/irv.13087","article-title":"Investigating confounding in network-based test-negative design influenza vaccine effectiveness studies-Experience from the DRIVE project","volume":"17","author":"Stuurman","year":"2023","journal-title":"Influenza Other Respir. Viruses"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1070","DOI":"10.1016\/j.vaccine.2016.01.002","article-title":"Seasonal influenza vaccine effectiveness estimates: Development of a parsimonious case test negative model using a causal approach","volume":"34","author":"Lane","year":"2016","journal-title":"Vaccine"},{"key":"ref_29","first-page":"2060","article-title":"Observational studies and the difficult quest for causality: Lessons from vaccine effectiveness and impact studies","volume":"45","author":"Lipsitch","year":"2016","journal-title":"Int. J. Epidemiol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"569","DOI":"10.1037\/0022-3514.54.4.569","article-title":"Outcome bias in decision evaluation","volume":"54","author":"Baron","year":"1988","journal-title":"J. Personal. Soc. Psychol."}],"container-title":["Vaccines"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-393X\/13\/10\/1047\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,14]],"date-time":"2025-10-14T04:28:16Z","timestamp":1760416096000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-393X\/13\/10\/1047"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,10,12]]},"references-count":30,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2025,10]]}},"alternative-id":["vaccines13101047"],"URL":"https:\/\/doi.org\/10.3390\/vaccines13101047","relation":{},"ISSN":["2076-393X"],"issn-type":[{"value":"2076-393X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,10,12]]}}}