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Low Levels of Neutralizing Antibodies Against SARS-CoV-2 KP.3.1.1 and XEC in Serum From Seniors in May 2024
Even Fossum1, Elisabeth Lea Vikse1, Anna Hayman Robertson2
1Department of Virology, Division of Infection Control, Norwegian Institute of Public Health, Oslo, Norway.
Abstract:
New immune evasive variants of SARS-CoV-2 may increase infections and hospitalizations in risk groups, such as the elderly. In this study, we evaluated neutralizing antibodies against KP.3.1.1 and XEC, virus variants that were either widely distributed or on the rise globally in the fall of 2024, in sera from a cohort of seniors aged 68-82 years collected in April/May 2024. Neutralizing responses were low against both KP.3.1.1 and XEC, also in XBB.1.5 boosted individuals and people with recent break-through infections, supporting the recommendation of an updated COVID-19 vaccine booster in this age group.
Insights
New SARS-CoV-2 variants KP.3.1.1 and XEC show low neutralization in seniors. Updated COVID-19 vaccine boosters are recommended for this vulnerable group to enhance protection against evolving immune-evasive strains.
Area of Science:
- Virology and immunology
- Epidemiology of infectious diseases
- Geriatric medicine
Background:
- Emerging SARS-CoV-2 variants pose a threat to vulnerable populations like the elderly.
- Immune evasion by new variants can lead to increased infections and hospitalizations.
- Understanding antibody responses in seniors is crucial for public health strategies.
Purpose of the Study:
- To assess neutralizing antibody levels against SARS-CoV-2 variants KP.3.1.1 and XEC in elderly individuals.
- To evaluate the effectiveness of existing immunity (from vaccination and infection) against these new variants.
- To inform recommendations for updated COVID-19 vaccine boosters in at-risk age groups.
Main Methods:
- Sera from seniors (aged 68-82 years) collected in April/May 2024 were tested.
- Neutralizing antibody responses were measured against SARS-CoV-2 variants KP.3.1.1 and XEC.
- Analysis included individuals boosted with XBB.1.5 and those with recent breakthrough infections.
Main Results:
- Neutralizing antibody responses against KP.3.1.1 and XEC were low in the studied senior cohort.
- Low neutralization was observed even in individuals previously boosted with XBB.1.5.
- Recent breakthrough infections did not confer significantly higher neutralizing activity against these variants.
Conclusions:
- Current immunity appears insufficient to neutralize emerging SARS-CoV-2 variants KP.3.1.1 and XEC in the elderly.
- An updated COVID-19 vaccine booster is strongly supported for this age group.
- Continued monitoring of variant evolution and immune responses is essential.
