The Association Between COVID-19 Vaccination History and the Incidence of COVID-19 and Healthcare Resource Use in Rural Residents in Japan
Author(s)
Ayako Shoji, PhD1, Yuriko Hagiwara, BSc, MSc, PhD1, Kenichi Kudo, BSc2, Koichi Murashita, M.A.3, Shigeyuki Nakaji, PhD3, Ataru Igarashi, PhD1;
1The University of Tokyo, Tokyo, Japan, 2ICI Inc., Tokyo, Japan, 3Hirosaki University, Hirosaki, Japan
1The University of Tokyo, Tokyo, Japan, 2ICI Inc., Tokyo, Japan, 3Hirosaki University, Hirosaki, Japan
OBJECTIVES: The vaccination for COVID-19 is currently recommended in a high-risk population; however, the vaccination rate is decreasing. This study aims to confirm the association between the vaccination and the incidence of COVID-19, healthcare resource use in 2022 when a high number of COVID-19 cases were observed in Japan.
METHODS: We used a claims data of insured residents and vaccination records in a rural area, which were individually linked under the next generation medical infrastructure low, only one framework to realize this linkage in Japan. We identified residents who continuously insured from 3-month before (baseline) to 9-month after (follow-up) the index date (1st July 2022) and classified them into vaccination and no vaccination groups based on the vaccination history within 6-month before the index date. We considered age, sex, and Charlson Comorbidity Index (CCI) as risk factors and compared the incidence of COVID-19 and pneumonia after the 1st diagnosis of COVID-19 and the number of months where intensive care unit (ICU) or artificial respiration (AR) was provided.
RESULTS: Of 76,549 eligible residents, the numbers of those in the with and without vaccination groups were 57,431 (75.0%) and 19,118 (25.0%), respectively. In the vaccination group, higher age (69.2 ± 15.9 vs 51.7 ± 25.3) and CCI score (1.7 ± 2.3 vs 0.8 ± 1.9) but slightly lower proportion of COVID-19 incidence (0.05 vs 0.06) were observed. After adjusting age, sex, and CCI score, the vaccination did not associate with the COVID-19 incidence (odds ratio [OR] = 1.01, p-value = 0.900) but significantly associated with the lower incidence of pneumonia after the onset of COVID-19 (OR = 0.75, p-value = 0.037) and the shorter ICU or AR treatment (risk ratio = 0.60, p-value < 0.001).
CONCLUSIONS: We observed a low incidence of pneumonia and severe symptoms in the vaccinated population.
METHODS: We used a claims data of insured residents and vaccination records in a rural area, which were individually linked under the next generation medical infrastructure low, only one framework to realize this linkage in Japan. We identified residents who continuously insured from 3-month before (baseline) to 9-month after (follow-up) the index date (1st July 2022) and classified them into vaccination and no vaccination groups based on the vaccination history within 6-month before the index date. We considered age, sex, and Charlson Comorbidity Index (CCI) as risk factors and compared the incidence of COVID-19 and pneumonia after the 1st diagnosis of COVID-19 and the number of months where intensive care unit (ICU) or artificial respiration (AR) was provided.
RESULTS: Of 76,549 eligible residents, the numbers of those in the with and without vaccination groups were 57,431 (75.0%) and 19,118 (25.0%), respectively. In the vaccination group, higher age (69.2 ± 15.9 vs 51.7 ± 25.3) and CCI score (1.7 ± 2.3 vs 0.8 ± 1.9) but slightly lower proportion of COVID-19 incidence (0.05 vs 0.06) were observed. After adjusting age, sex, and CCI score, the vaccination did not associate with the COVID-19 incidence (odds ratio [OR] = 1.01, p-value = 0.900) but significantly associated with the lower incidence of pneumonia after the onset of COVID-19 (OR = 0.75, p-value = 0.037) and the shorter ICU or AR treatment (risk ratio = 0.60, p-value < 0.001).
CONCLUSIONS: We observed a low incidence of pneumonia and severe symptoms in the vaccinated population.
Conference/Value in Health Info
2025-05, ISPOR 2025, Montréal, Quebec, CA
Value in Health, Volume 28, Issue S1
Code
EPH43
Topic
Epidemiology & Public Health
Topic Subcategory
Public Health
Disease
No Additional Disease & Conditions/Specialized Treatment Areas, STA: Vaccines