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Silent battles: immune responses in asymptomatic SARS-CoV-2 infection

Cellular & Molecular Immunology volume 21, pages 159–170 (2024)Cite this article

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Abstract

SARS-CoV-2 infections manifest with a broad spectrum of presentations, ranging from asymptomatic infections to severe pneumonia and fatal outcomes. This review centers on asymptomatic infections, a widely reported phenomenon that has substantially contributed to the rapid spread of the pandemic. In such asymptomatic infections, we focus on the role of innate, humoral, and cellular immunity. Notably, asymptomatic infections are characterized by an early and robust innate immune response, particularly a swift type 1 IFN reaction, alongside a rapid and broad induction of SARS-CoV-2-specific T cells. Often, antibody levels tend to be lower or undetectable after asymptomatic infections, suggesting that the rapid control of viral replication by innate and cellular responses might impede the full triggering of humoral immunity. Even if antibody levels are present in the early convalescent phase, they wane rapidly below serological detection limits, particularly following asymptomatic infection. Consequently, prevalence studies reliant solely on serological assays likely underestimate the extent of community exposure to the virus.

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Fig. 1: Ratio between the prevalence of antibodies and the total number of reported cases in different geographical regions.
Fig. 2: COVID-19 infection–fatality ratio by age and geography.
Fig. 3: Proportion of asymptomatic and symptomatic SARS-CoV-2 infection by age and geography.
Fig. 4: Immune responses in asymptomatic and symptomatic SARS-CoV-2 infection.
Fig. 5: Estimating infection rates among asymptomatics by measuring SARS-CoV-2-specific antibodies and T cells.

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Authors and Affiliations

  1. Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore, Singapore

    Nina Le Bert & Taraz Samandari

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  1. Nina Le Bert
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  2. Taraz Samandari
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Correspondence to Nina Le Bert.

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Competing interests

NLB declares a patent application for a method to monitor SARS-CoV-2-specific T cells in biological samples pending, and she is a co-founder of T Cell Diagnostics (TCD) Ltd. TS declares no competing interests.

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Le Bert, N., Samandari, T. Silent battles: immune responses in asymptomatic SARS-CoV-2 infection. Cell Mol Immunol 21, 159–170 (2024). https://doi.org/10.1038/s41423-024-01127-z

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  • DOI: https://doi.org/10.1038/s41423-024-01127-z

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