2025/05/26 by Nelson Lee, Lena Nguyen, Sharifa Nasreen +9 · 1 voice · 1 citation
Agricultural and Biological Sciences · Medicine · #Animal Virus Infections Studies #Influenza Virus Research Studies #SARS-CoV-2 and COVID-19 Research
paper · doi:10.1016/j.vaccine.2025.127300
openalex publication_date 2025/05/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We estimated XBB.1.5 vaccine effectiveness (VE) against hospitalization/death among adults aged ≥50 years in Ontario, Canada, from September 2023 to June 2024. Compared with non-XBB.1.5 vaccinees, the initial protection at 0-3 months was 64 % (95 %CI, 57 %-69 %) during XBB-sublineage predominance. It was reduced to 57 % (95 %CI, 48 %-64 %) when JN/KP-sublineages became predominant, and quickly declined. No significant protection was observed >6 months post-vaccination. The VE estimates were lower when the last vaccine dose in the reference group was given more recently than 12 months, or was the omicron-containing bivalent vaccine. Short durability of protection poses unique challenges for COVID-19 vaccination.