Reduction in COVID-19 Vaccine Effectiveness against SARS-CoV-2 Variants in Seoul according to Age, Sex, and Symptoms: A Test-Negative Case-Control Study

Hyerin Gim, Soyoung Oh, Heeda Lee, Seul Lee, Haesook Seo, Yumi Park () and Jae-Hyun Park ()
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Hyerin Gim: Infectious Disease Research Center, Citizen’s Health Bureau, Seoul Metropolitan Government, 110, Sejong-daero, Jung-gu, Seoul 04524, Republic of Korea
Soyoung Oh: Infectious Disease Research Center, Citizen’s Health Bureau, Seoul Metropolitan Government, 110, Sejong-daero, Jung-gu, Seoul 04524, Republic of Korea
Heeda Lee: Infectious Disease Research Center, Citizen’s Health Bureau, Seoul Metropolitan Government, 110, Sejong-daero, Jung-gu, Seoul 04524, Republic of Korea
Seul Lee: Infectious Disease Research Center, Citizen’s Health Bureau, Seoul Metropolitan Government, 110, Sejong-daero, Jung-gu, Seoul 04524, Republic of Korea
Haesook Seo: Infectious Disease Research Center, Citizen’s Health Bureau, Seoul Metropolitan Government, 110, Sejong-daero, Jung-gu, Seoul 04524, Republic of Korea
Yumi Park: Citizen’s Health Bureau, Seoul Metropolitan Government, 110, Sejong-daero, Jung-gu, Seoul 04524, Republic of Korea
Jae-Hyun Park: Department of Social and Preventive Medicine, Sungkyunkwan University School of Medicine, 2066 Seobu-ro, Jangan-gu, Suwon 16419, Republic of Korea

IJERPH, 2022, vol. 19, issue 24, 1-15

Abstract: Background: We evaluated vaccine effectiveness (VE) against infections with SARS-CoV-2 variants of concern in Seoul, the capital of the Republic of Korea, having the highest population density in the country, under real-world conditions. Methods: We evaluated the reduction in the effectiveness of mRNA and viral-vector COVID-19 vaccines against infection by the SARS-CoV-2 delta variant in a subpopulation from April 2021 to July 2021 who visited screening clinics in Seoul using a test-negative case-control study design. Moreover, we conducted a case-control study matching the ten-year-old age group, sex, healthcare workers, and five districts of Seoul, which are considered confounding factors. Results: The full VE in the pre-delta-dominant period was 95.0% (95% confidence interval [CI]: 91.2–97.2); however, it decreased to 61.1% (95% CI: 53.2–67.6) during the delta-dominant period. Notably, we found that COVID-19 VE was significantly decreased in individuals aged ≥80 years (52.9%, 95% CI: −9.9–79.8), men (50.6 %, 95% CI: 39.4–59.8), and asymptomatic individuals (49.8%, 95% CI: 36.5–60.3) during the widespread SARS-CoV-2 delta variant circulation. Conclusions: Vaccine-mediated protection drastically declined during the delta-dominant period and in vulnerable groups. This study suggests the requirement for additional countermeasures, such as the administration of a booster vaccine, in vulnerable groups based on age, sex, and symptomatic manifestation.

Keywords: COVID-19; mRNA vaccines; adenovirus vaccines; vaccine efficiency; risk factors (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2022
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