Real-World Effectiveness of Boosting Against Omicron Hospitalization in Older Adults, Stratified by Frailty
Background/Objectives: Older adults with frailty are at-risk of worse outcomes following respiratory-viral-infections such as COVID-19. Data on effectiveness of vaccination/boosting in frail older adults during Omicron is lacking. Methods: National healthcare-claims data and COVID-19 registries were...
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MDPI AG
2025-05-01
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| Series: | Vaccines |
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| Online Access: | https://www.mdpi.com/2076-393X/13/6/565 |
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| author | Liang En Wee Enoch Xue Heng Loy Jue Tao Lim Wei Hao Kwok Calvin Chiew Christopher Lien Barbara Helen Rosario Ian Yi Onn Leong Reshma Aziz Merchant David Chien Boon Lye Kelvin Bryan Tan |
| author_facet | Liang En Wee Enoch Xue Heng Loy Jue Tao Lim Wei Hao Kwok Calvin Chiew Christopher Lien Barbara Helen Rosario Ian Yi Onn Leong Reshma Aziz Merchant David Chien Boon Lye Kelvin Bryan Tan |
| author_sort | Liang En Wee |
| collection | DOAJ |
| description | Background/Objectives: Older adults with frailty are at-risk of worse outcomes following respiratory-viral-infections such as COVID-19. Data on effectiveness of vaccination/boosting in frail older adults during Omicron is lacking. Methods: National healthcare-claims data and COVID-19 registries were utilized to enroll a cohort of older Singaporeans (≥60 years) as of 1 January 2022, divided into low/intermediate/high-risk for frailty; matching weights were utilized to adjust for sociodemographic differences/vaccination uptake at enrolment across frailty categories. Competing-risk-regression (Fine-Gray) taking death as a competing risk, with matching weights applied, was utilized to compare risks of COVID-19-related hospitalizations and severe COVID-19 across frailty levels (low/intermediate/high-risk), with estimates stratified by booster status. Individuals were followed up until study end-date (20 December 2023). Results: 874,160 older adults were included during Omicron-predominant transmission; ~10% had intermediate/high-frailty-risk. Risk of hospitalization/severe COVID-19 was elevated in those with intermediate/high-frailty-risk up to XBB/JN.1 transmission. Boosting was associated with decreased risk of COVID-19-related hospitalization across all frailty categories in infection-naïve individuals. However, in infection-naïve older adults with high-frailty-risk, while receipt of first boosters was associated with lower risk of COVID-19-hospitalization/severe COVID-19, additional booster doses did not reduce risk. In reinfected older adults, first boosters were still associated with lower hospitalization risk (adjusted-hazards-ratio, aHR = 0.55, 95% CI = 0.33–0.92) among the non-frail, but not in the intermediate/high-frailty-risk minority. Conclusions: First boosters were associated with reduced adverse COVID-19 outcomes across all frailty categories in infection-naïve older adults during Omicron. However, in the high-frailty minority, boosting did not additionally reduce risk in reinfected individuals with hybrid immunity, and beyond the first booster for infection-naïve individuals. |
| format | Article |
| id | doaj-art-be5afd8f6d5a4026bf273c7b25fc07fa |
| institution | Kabale University |
| issn | 2076-393X |
| language | English |
| publishDate | 2025-05-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Vaccines |
| spelling | doaj-art-be5afd8f6d5a4026bf273c7b25fc07fa2025-08-20T03:26:56ZengMDPI AGVaccines2076-393X2025-05-0113656510.3390/vaccines13060565Real-World Effectiveness of Boosting Against Omicron Hospitalization in Older Adults, Stratified by FrailtyLiang En Wee0Enoch Xue Heng Loy1Jue Tao Lim2Wei Hao Kwok3Calvin Chiew4Christopher Lien5Barbara Helen Rosario6Ian Yi Onn Leong7Reshma Aziz Merchant8David Chien Boon Lye9Kelvin Bryan Tan10National Centre for Infectious Diseases, Singapore 308442, SingaporeNational Centre for Infectious Diseases, Singapore 308442, SingaporeLee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, SingaporeNational Centre for Infectious Diseases, Singapore 308442, SingaporeNational Centre for Infectious Diseases, Singapore 308442, SingaporeDepartment of Geriatric Medicine, Changi General Hospital, Singapore 529889, SingaporeDepartment of Geriatric Medicine, Changi General Hospital, Singapore 529889, SingaporeLee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, SingaporeDivision of Geriatric Medicine, Department of Medicine, National University Hospital, Singapore 119074, SingaporeNational Centre for Infectious Diseases, Singapore 308442, SingaporeNational Centre for Infectious Diseases, Singapore 308442, SingaporeBackground/Objectives: Older adults with frailty are at-risk of worse outcomes following respiratory-viral-infections such as COVID-19. Data on effectiveness of vaccination/boosting in frail older adults during Omicron is lacking. Methods: National healthcare-claims data and COVID-19 registries were utilized to enroll a cohort of older Singaporeans (≥60 years) as of 1 January 2022, divided into low/intermediate/high-risk for frailty; matching weights were utilized to adjust for sociodemographic differences/vaccination uptake at enrolment across frailty categories. Competing-risk-regression (Fine-Gray) taking death as a competing risk, with matching weights applied, was utilized to compare risks of COVID-19-related hospitalizations and severe COVID-19 across frailty levels (low/intermediate/high-risk), with estimates stratified by booster status. Individuals were followed up until study end-date (20 December 2023). Results: 874,160 older adults were included during Omicron-predominant transmission; ~10% had intermediate/high-frailty-risk. Risk of hospitalization/severe COVID-19 was elevated in those with intermediate/high-frailty-risk up to XBB/JN.1 transmission. Boosting was associated with decreased risk of COVID-19-related hospitalization across all frailty categories in infection-naïve individuals. However, in infection-naïve older adults with high-frailty-risk, while receipt of first boosters was associated with lower risk of COVID-19-hospitalization/severe COVID-19, additional booster doses did not reduce risk. In reinfected older adults, first boosters were still associated with lower hospitalization risk (adjusted-hazards-ratio, aHR = 0.55, 95% CI = 0.33–0.92) among the non-frail, but not in the intermediate/high-frailty-risk minority. Conclusions: First boosters were associated with reduced adverse COVID-19 outcomes across all frailty categories in infection-naïve older adults during Omicron. However, in the high-frailty minority, boosting did not additionally reduce risk in reinfected individuals with hybrid immunity, and beyond the first booster for infection-naïve individuals.https://www.mdpi.com/2076-393X/13/6/565SARS-CoV-2Omicronvaccinationboostingfrailtygeriatrics |
| spellingShingle | Liang En Wee Enoch Xue Heng Loy Jue Tao Lim Wei Hao Kwok Calvin Chiew Christopher Lien Barbara Helen Rosario Ian Yi Onn Leong Reshma Aziz Merchant David Chien Boon Lye Kelvin Bryan Tan Real-World Effectiveness of Boosting Against Omicron Hospitalization in Older Adults, Stratified by Frailty Vaccines SARS-CoV-2 Omicron vaccination boosting frailty geriatrics |
| title | Real-World Effectiveness of Boosting Against Omicron Hospitalization in Older Adults, Stratified by Frailty |
| title_full | Real-World Effectiveness of Boosting Against Omicron Hospitalization in Older Adults, Stratified by Frailty |
| title_fullStr | Real-World Effectiveness of Boosting Against Omicron Hospitalization in Older Adults, Stratified by Frailty |
| title_full_unstemmed | Real-World Effectiveness of Boosting Against Omicron Hospitalization in Older Adults, Stratified by Frailty |
| title_short | Real-World Effectiveness of Boosting Against Omicron Hospitalization in Older Adults, Stratified by Frailty |
| title_sort | real world effectiveness of boosting against omicron hospitalization in older adults stratified by frailty |
| topic | SARS-CoV-2 Omicron vaccination boosting frailty geriatrics |
| url | https://www.mdpi.com/2076-393X/13/6/565 |
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