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Communicable diseases

COVID-19 Vaccine Efficacy in Older Adults Raises Concerns Over Emerging Variants

Strategic Insights

— 1 min read

As the global community grapples with the persistence of the SARS-CoV-2 virus, a new study from Quzhou, People's Republic of China, sheds light on the efficacy of existing COVID-19 vaccines in older adults. The research, published in Signal Transduction and Targeted Therapy, reveals that while XBB-containing vaccine-induced immunity remains detectable in most participants, it experiences a significant decline over time, highlighting the need for updates in booster formulations and improved vaccine designs.

Key Takeaways:

  • The study assessed the neutralizing antibody (nAb) responses in a cohort of 90 older adults aged 65 years, who received a single booster dose of trivalent XBB.1.5, bivalent Omicron XBB, or tetravalent XBB.1 vaccines.
  • Six months post-vaccination, the nAb titers decreased over time, with 2.5-4.6-fold reductions in the geometric mean titer against the variants KP.3.1.1 and XEC.
  • The Tri-XBB.1.5 vaccine exhibited marginally better antibody persistence than the Bi-Omi-XBB and Tetra-XBB.1 vaccines, suggesting potential formulation-dependent differences in long-term immunogenicity.
  • Twenty-seven participants experienced SARS-CoV-2 infection, including 11 (12.2%) confirmed by rapid antigen testing and 16 (17.8%) classified as probably based on serological evidence.
  • Lower nAb titers on day 21 were linked to early infections, whereas late infections reflected antibody waning.
  • Infections transiently increased nAb levels, but the elevated titers were not sustained.
  • The study emphasized the importance of updating booster formulations and improving vaccine designs to address emerging immune-evasive variants.

Statistics:

  • The study involved 90 older adults aged 65 years.
  • The nAb titers decreased over time, with 2.5-4.6-fold reductions in the geometric mean titer against the variants KP.3.1.1 and XEC.
  • Twenty-seven participants experienced SARS-CoV-2 infection, representing 30% of the cohort.

Sources:

  • Signal Transduction and Targeted Therapy. (2025). Neutralizing Antibody Durability and SARS-CoV-2 Infection in Older Adults Six Months After XBB-Containing Vaccine Booster. 10(1), 336. doi: 10.1038/s41392-025-00734-2
  • Medical Letter on the CDC & FDA. (2025, October 26). New Findings from Department of Infectious Disease Control and Prevention Yields New Data on COVID-19 (Neutralizing Antibody Durability and SARS-CoV-2 Infection in Older Adults Six Months After XBB-Containing Vaccine Booster). 114.

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