Arashiro, Takeshi

Arima, Yuzo

Arioka, Hiroko

Ariyoshi, Koya

Chubachi, Kumi

Hibberd, Martin

Ihara, Genei

Kato, Hideaki

Kato, Yasuyuki

Kuramochi, Jin

Muraoka, Hirokazu

Nagura, Yoshito

Nidaira, Yuki

Nishida, Yusuke

Numata, Akira

Oba, Kunihiro

Oka, Hideaki

Ooki, Takao

Sato, Akihiro

Smith, Chris

Stucky, Ashley

Suzuki, Motoi

Suzuki, Tadaki

Ueda, Akihiro

Uehara, Yuki

Yanagisawa, Naoki

Yanai, Atsushi

Yanai, Hideki

LSHTM Research Online

1www.eurosurveillance.orgLetterLetter to the editor: Importance of considering high-risk behaviours in COVID-19 vaccine effectiveness estimates with observational studiesTakeshi Arashiro1,2,3,4 , Yuzo Arima¹ , Jin Kuramochi5,6 , Hirokazu Muraoka⁷ , Akihiro Sato⁸ , Kumi Chubachi⁹ , Kunihiro Oba10 , Atsushi Yanai11 , Hiroko Arioka11 , Yuki Uehara12,13 , Genei Ihara14 , Yasuyuki Kato15 , Naoki Yanagisawa16 , Yoshito Nagura17 , Hideki Yanai18 , Akihiro Ueda19 , Akira Numata20 , Hideaki Kato21 , Hideaki Oka22 , Yusuke Nishida22 , Takao Ooki23 , Yuki Nidaira⁵ , Ashley Stucky¹ , Tadaki Suzuki² , Chris Smith3,4 , Martin Hibberd³ , Koya Ariyoshi⁴ , Motoi Suzuki¹1. Center for Surveillance, Immunization, and Epidemiologic Research, National Institute of Infectious Diseases, Tokyo, Japan2. Department of Pathology, National Institute of Infectious Diseases, Tokyo, Japan3. Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom4. School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan5. Kuramochi Clinic Interpark, Tochigi, Japan6. Department of Global Health Promotion, Tokyo Medical and Dental University, Tokyo, Japan7. CLINIC FOR Tamachi, Tokyo, Japan8. KARADA Internal Medicine Clinic, Tokyo, Japan9. Chubachi Internal Respiratory Medicine Clinic, Tokyo, Japan10. Department of Pediatrics, Showa General Hospital, Tokyo, Japan11. Department of General Internal Medicine, St. Luke’s International Hospital, Tokyo, Japan12. Department of Clinical Laboratory, St. Luke’s International Hospital, Tokyo, Japan13. Department of Infectious Diseases, Fujita Health University School of Medicine, Aichi, Japan14. Machida Ekimae Naika Clinic, Tokyo, Japan15. Department of Infectious Diseases, International University of Health and Welfare Narita Hospital, Chiba, Japan16. Yanagisawa Clinic, Tokyo, Japan17. Shinjuku Home Clinic, Tokyo, Japan18. Fukujuji Hospital, Japan Anti-Tuberculosis Association, Kiyose, Japan19. Department of Infectious Diseases, Japanese Red Cross Medical Center, Tokyo, Japan20. Ikebukuro Metropolitan Clinic, Tokyo, Japan21. Infection Prevention and Control Department, Yokohama City University Hospital, Yokohama, Japan22. Department of General Internal Medicine and Infectious Diseases, Saitama Medical Center, Saitama, Japan23. Saitama Sekishinkai Hospital, Saitama, JapanCorrespondence: Takeshi Arashiro (arashirot@niid.go.jp)Citation style for this article:  Arashiro Takeshi, Arima Yuzo, Kuramochi Jin, Muraoka Hirokazu, Sato Akihiro, Chubachi Kumi, Oba Kunihiro, Yanai Atsushi, Arioka Hiroko, Uehara Yuki, Ihara Genei, Kato Yasuyuki, Yanagisawa Naoki, Nagura Yoshito, Yanai Hideki, Ueda Akihiro, Numata Akira, Kato Hideaki, Oka Hideaki, Nishida Yusuke, Ooki Takao, Nidaira Yuki, Stucky Ashley, Suzuki Tadaki, Smith Chris, Hibberd Martin, Ariyoshi Koya, Suzuki Motoi. Letter to the editor: Importance of considering high-risk behaviours in COVID-19 vaccine effectiveness estimates with observational studies. Euro Surveill. 2023;28(4):pii=2300034. https://doi.org/10.2807/1560-7917.ES.2023.28.4.2300034 Article submitted on 16 Jan 2023 / accepted on 24 Jan 2023 / published on 26 Jan 2023To the editor: We read with interest the article by van Ewijk et al. [1] regarding the influence of people’s behaviour on vaccine effectiveness (VE) estimates against coronavirus disease (COVID-19). We commend the authors’ effort in prospectively collecting detailed exposure history. The authors concluded that it is not necessary to collect data on risk behaviour in a test-negative case–control study, but we believe this con-clusion is not fully supported by the data. The VE may be underestimated when there is relaxation of mask/physical distancing policies only among vaccinees or implementation of domestic vaccine certificates/passports to allow vaccinees to engage in high-risk behaviours, as outlined in World Health Organization guidance [2]. In fact, the Netherlands used a ‘corona-virus entry pass’ from 25 September 2021 (midway through the study period), requiring visitors to pre-sent the pass at bars, restaurants, events and cultural venues [3]. If the authors had captured this exposure information (i.e. high-risk behaviours associated with this pass), they would probably have seen differing VE estimates with and without adjustments for high-risk behaviours as only the vaccinated would have been allowed to engage in these behaviours. Conversely and counterintuitively, in Table 1, the test-positive group exhibited more frequent mask wearing and more indi-viduals without close contact. The questionnaire could have perhaps asked for more specific exposures such as visiting restaurants/bars, in line with the coronavi-rus entry pass and previous reports that showed these activities to be high-risk [4,5]. Furthermore, observed waning immunity may partially be due to the introduc-tion of the coronavirus entry pass halfway through the study (i.e. spurious waning), which could have been accounted for with the collection of specific exposures.There is a previously published report suggesting that policies differentially targeting the vaccinated and unvaccinated would alter VE estimates. A study in New York showed that VE estimates declined simultaneously 2 www.eurosurveillance.orgacross different time cohorts after lifting mask man-dates exclusively for fully vaccinated individuals, which cannot be explained by waning immunity [6]. Although this potential association was ecological in nature, the study suggested that behavioural changes such as mask wearing may influence VE estimates.We previously published a similar study adjusting for high-risk behaviours and mask wearing as well as testing behaviour [7]. We also did not see a large difference in COVID-19 VE estimates before and after adjusting for behaviours. This is expected because the Japanese government did not introduce policies differ-entially targeting the vaccinated and unvaccinated; and our incorporation of high-risk behaviours and mask wearing as covariates strengthened our observational findings. We also did an exploratory secondary analy-sis to estimate VEs of 2-dose mRNA vaccine recipients among those who did or did not engage in high-risk behaviours (dining at restaurants/bars at night with alcohol consumption in a group was used as a proxy [5]) compared with unvaccinated individuals who did not engage in high-risk behaviours during the BA.1/BA.2-dominant period, assuming a hypothetical sce-nario of vaccine passport introduction. The resulting VE estimate was significantly lower among vaccinees with high-risk behaviours (36%; 95% confidence inter-val (CI): 14–53) than among vaccinees with no high-risk behaviours (56%; 95% CI: 41–67; p < 0.001), indicat-ing that VE can be underestimated by 20% via vaccine passport introduction.When estimating VE, we assume a causal relationship between vaccination and infection/disease [8] and we rely on observational studies as trials are often not ethically possible. Therefore, we need to carefully con-sider potential confounders and biases in the design and analysis. These potential confounders are not uni-form for any disease or context. This notion is becom-ing increasingly important as infectious diseases are attracting the attention of the public and influencing behaviours, while more observational studies utilise existing data sources, which may not always contain the information necessary for the appropriate analysis.Conflict of interestTakeshi Arashiro is an unpaid consultant for the World Health Organization. The other authors declare no conflicts of interest.Authors’ contributionsConception: TA, YA, JK, HM, ASa, KC, KO, AY, HA, YU, GI, YK, NY, YNa, HY, AU, AN, HK, HO, YNis, TO, YNid, ASt, TS, CS, MH, KA, MS.Drafting of the manuscript: TA.Critical revision of the manuscript for important intellectual content: TA, YA, JK, HM, ASa, KC, KO, AY, HA, YU, GI, YK, NY, YNa, HY, AU, AN, HK, HO, YNis, TO, YNid, ASt, TS, CS, MH, KA, MS.References1. van Ewijk CE, Kooijman MN, Fanoy E, Raven SF, Middeldorp M, Shah A, et al. COVID-19 vaccine effectiveness against SARS-CoV-2 infection during the Delta period, a nationwide study adjusting for chance of exposure, the Netherlands, July to December 2021. Euro Surveill. 2022;27(45):2200217.  https://doi.org/10.2807/1560-7917.ES.2022.27.45.2200217  PMID: 36367011 2. World Health Organization (WHO). Evaluation of COVID-19 vaccine effectiveness in a changing landscape of COVID-19 epidemiology and vaccination: interim guidance, 1 October 2022: second addendum to Evaluation of COVID-19 vaccine effectiveness: interim guidance. Geneva: WHO; 2022. Available from: https://apps.who.int/iris/handle/10665/3633443. Government of the Netherlands. Netherlands to reopen further with coronavirus entry passes. Amsterdam: Government of the Netherlands; 2021. Available from: https://www.government.nl/latest/news/2021/09/14/netherlands-to-reopen-further-with-coronavirus-entry-passes4. Fisher KA, Tenforde MW, Feldstein LR, Lindsell CJ, Shapiro NI, Files DC, et al. Community and close contact exposures associated with COVID-19 among symptomatic adults ≥18 years in 11 outpatient health care facilities – United States, July 2020. MMWR Morb Mortal Wkly Rep. 2020;69(36):1258-64.  https://doi.org/10.15585/mmwr.mm6936a5  PMID: 32915165 5. Arashiro T, Arima Y, Muraoka H, Sato A, Oba K, Uehara Y, et al. Behavioral factors associated with SARS-CoV-2 infection in Japan. Influenza Other Respir Viruses. 2022;16(5):952-61.  https://doi.org/10.1111/irv.12992  PMID: 35470969 6. Rosenberg ES, Dorabawila V, Easton D, Bauer UE, Kumar J, Hoen R, et al. COVID-19 vaccine effectiveness by product and timing in New York State. medRxiv.  https://doi.org/10.1101/2021.10.08.21264595 7. Arashiro T, Arima Y, Muraoka H, Sato A, Oba K, Uehara Y, et al. COVID-19 vaccine effectiveness against symptomatic SARS-CoV-2 infection during Delta-dominant and Omicron-dominant periods in Japan: a multi-center prospective case-control study (FASCINATE study). Clin Infect Dis. 2022;ciac635.  https://doi.org/10.1093/cid/ciac635  PMID: 35918782 8. Sullivan SG, Cowling BJ. “Crude vaccine effectiveness” is a misleading term in test-negative studies of influenza vaccine effectiveness. Epidemiology. 2015;26(5):e60.  https://doi.org/10.1097/EDE.0000000000000343  PMID: 26133018License, supplementary material and copyrightThis is an open-access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0) Licence. You may share and adapt the material, but must give appropriatecredit to the source, provide a link to the licence and indicate if changes were made. Any supplementary material referenced in the article can be found in the online version.This article is copyright of the authors or their affiliated in-stitutions, 2023.

Letter to the editor: Importance of considering high-risk behaviours in COVID-19 vaccine effectiveness estimates with observational studies.

https://researchonline.lshtm.ac.uk/id/eprint/4668595/7/Arashiro_etal_2023_Importance-of-considering-high-risk.pdf

Letter to the editor: Importance of considering high-risk behaviours in COVID-19 vaccine effectiveness estimates with observational studies.

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