tetano
Editor, Senior Moderator
Clin Microbiol Infect
. 2025 Oct 29:S1198-743X(25)00514-2.
doi: 10.1016/j.cmi.2025.10.013. Online ahead of print. Real-world effectiveness of influenza vaccination and subsequent waning in a tropical setting: a retrospective cohort study
Liang En Wee[SUP] 1 [/SUP], Reen Wan Li Ho[SUP] 2 [/SUP], Jue Tao Lim[SUP] 3 [/SUP], Calvin J Chiew[SUP] 4 [/SUP], Benjamin Ong[SUP] 5 [/SUP], Zubaidah Said[SUP] 4 [/SUP], Soon Kok Lim[SUP] 4 [/SUP], Barnaby Young[SUP] 6 [/SUP], David Chien Boon Lye[SUP] 7 [/SUP], Kelvin Bryan Tan[SUP] 8 [/SUP]
Affiliations
Objectives: Information on influenza vaccine-effectiveness in tropical regions with year-round influenza transmission remains scarce. We evaluated real-world influenza vaccine-effectiveness in a tropical setting following resurgence of influenza activity post-COVID-19, assessing impact of repeated vaccination on vaccine-effectiveness and waning.
Methods: Population-based retrospective cohort study, including all adult Singaporeans (1[SUP]st[/SUP] May 2022-30[SUP]th[/SUP] April 2024). Person-time was divided into vaccinated (<365 days prior), and unvaccinated/vaccinated≥365 days prior, using the National-Immunisation-Registry. Cox regression, with overlap weights applied, was utilised to evaluate hazards-ratio (HR) of influenza hospitalisation between vaccinated/unvaccinated groups. Vaccine-effectiveness was calculated as 1-HR. Relative waning of vaccine-effectiveness in older adults (≥65 years) was separately evaluated via logistic regression, using weeks 2-9 post-vaccination as reference, and stratified by prior doses (1/2/≥3 doses) in the past 2 years.
Findings: 3,445,961 adult Singaporeans (≥18 years) were included, comprising 6,245,014 vaccinated/unvaccinated observations over 1,376,225,223 person-days. Overall vaccine-effectiveness against influenza hospitalisation was 37% (95%CI=32-42%) amongst older adults (≥65 years). However, relative vaccine-effectiveness waned to 43%(95%CI=34-54%) by 18-25 weeks post-vaccination. Receipt of ≥2 vaccine doses in the preceding 2 years was associated with lower odds of vaccine-failure (adjusted odds-ratio, aOR=0.81[95%CI=0.71-0.91]); no significant waning was observed in those who cumulatively received ≥3 vaccine doses over 2 years.
Conclusion: Vaccine-effectiveness against influenza hospitalisation was estimated at 37% in a tropical setting with year-round influenza transmission, though protection waned by ≥50% 6 months post-vaccination. No significant waning was observed in those who received ≥3 vaccine doses over 2 years; increased re-vaccination frequency may mitigate waning in tropical settings.
Keywords: Influenza; immunocompromised; tropical; vaccination; vaccine-effectiveness; waning.
. 2025 Oct 29:S1198-743X(25)00514-2.
doi: 10.1016/j.cmi.2025.10.013. Online ahead of print. Real-world effectiveness of influenza vaccination and subsequent waning in a tropical setting: a retrospective cohort study
Liang En Wee[SUP] 1 [/SUP], Reen Wan Li Ho[SUP] 2 [/SUP], Jue Tao Lim[SUP] 3 [/SUP], Calvin J Chiew[SUP] 4 [/SUP], Benjamin Ong[SUP] 5 [/SUP], Zubaidah Said[SUP] 4 [/SUP], Soon Kok Lim[SUP] 4 [/SUP], Barnaby Young[SUP] 6 [/SUP], David Chien Boon Lye[SUP] 7 [/SUP], Kelvin Bryan Tan[SUP] 8 [/SUP]
Affiliations
- PMID: 41173339
- DOI: 10.1016/j.cmi.2025.10.013
Objectives: Information on influenza vaccine-effectiveness in tropical regions with year-round influenza transmission remains scarce. We evaluated real-world influenza vaccine-effectiveness in a tropical setting following resurgence of influenza activity post-COVID-19, assessing impact of repeated vaccination on vaccine-effectiveness and waning.
Methods: Population-based retrospective cohort study, including all adult Singaporeans (1[SUP]st[/SUP] May 2022-30[SUP]th[/SUP] April 2024). Person-time was divided into vaccinated (<365 days prior), and unvaccinated/vaccinated≥365 days prior, using the National-Immunisation-Registry. Cox regression, with overlap weights applied, was utilised to evaluate hazards-ratio (HR) of influenza hospitalisation between vaccinated/unvaccinated groups. Vaccine-effectiveness was calculated as 1-HR. Relative waning of vaccine-effectiveness in older adults (≥65 years) was separately evaluated via logistic regression, using weeks 2-9 post-vaccination as reference, and stratified by prior doses (1/2/≥3 doses) in the past 2 years.
Findings: 3,445,961 adult Singaporeans (≥18 years) were included, comprising 6,245,014 vaccinated/unvaccinated observations over 1,376,225,223 person-days. Overall vaccine-effectiveness against influenza hospitalisation was 37% (95%CI=32-42%) amongst older adults (≥65 years). However, relative vaccine-effectiveness waned to 43%(95%CI=34-54%) by 18-25 weeks post-vaccination. Receipt of ≥2 vaccine doses in the preceding 2 years was associated with lower odds of vaccine-failure (adjusted odds-ratio, aOR=0.81[95%CI=0.71-0.91]); no significant waning was observed in those who cumulatively received ≥3 vaccine doses over 2 years.
Conclusion: Vaccine-effectiveness against influenza hospitalisation was estimated at 37% in a tropical setting with year-round influenza transmission, though protection waned by ≥50% 6 months post-vaccination. No significant waning was observed in those who received ≥3 vaccine doses over 2 years; increased re-vaccination frequency may mitigate waning in tropical settings.
Keywords: Influenza; immunocompromised; tropical; vaccination; vaccine-effectiveness; waning.