Limited durability of protection conferred by XBB.1.5 vaccines against Omicron-associated severe outcomes among community-dwelling adults aged ≥50 years, Ontario, Canada, September 2023 to June 2024

  1. Nelson Lee
  2. Lena Nguyen
  3. Sharifa Nasreen
  4. Peter C. Austin
  5. Kevin A. Brown
  6. Sarah A Buchan
  7. Ramandip Grewal
  8. Kevin L Schwartz
  9. Mina Tadrous
  10. Kumanan Wilson
  11. Sarah E Wilson
  12. Jeffrey C Kwong
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Abstract

We estimated XBB.1.5 vaccine effectiveness against hospitalization/death among adults aged ≥50 years. Compared with non-XBB.1.5 vaccinees, the initial protection of 64% (95%CI, 57%−69%) was reduced when JN/KP-sublineages became predominant, and quickly declined. No significant protection was observed >6 months post-vaccination. Short durability of protection poses unique challenges for COVID-19 vaccination.

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  1. Version published to 10.1101/2024.12.14.24318807v1 on medRxiv