Factors influencing the immune response over 15 months after SARS-CoV-2 infection: A longitudinal population-wide study in the Faroe Islands

J Intern Med. 2022 Aug 23. doi: 10.1111/joim.13560. Online ahead of print.

ABSTRACT

BACKGROUND: The durability of SARS-CoV-2 antibody response and the resulting immunity to COVID-19 is unclear.

OBJECTIVES: To investigate long-term humoral immunity to SARS-CoV-2.

METHODS: In this nationwide, longitudinal study we determined antibody response in 411 patients aged 0-93 years from two waves of infections (March to December 2020) contributing with 1063 blood samples. Each individual had blood drawn on four-five occasions 1-15 months after disease onset. We measured total anti-SARS-CoV-2 receptor-binding domain(RBD) antibody IgM, IgG, IgA using a qualitative RBD sandwich ELISA and neutralizing antibodies(NAbs) using an in-house ELISA-based pseudo-neutralizing assay. IgG subclasses were analysed in a subset of samples by ELISA-based assay. We used non-linear models to study the durability of SARS-CoV-2 antibody responses and its influence over time.

RESULTS: After 15 months, 94% still had detectable circulating antibodies, mainly the IgG isotype, and 92% had detectable NAbs. The distribution of IgG antibodies varied significantly over time, characterized by a biphasic pattern with an initial decline followed by a plateau after approximately seven months. However, the NAbs remained relatively stable throughout the period. The strength of the antibody response was influenced by smoking and hospitalization, with lower IgG levels in smokers and higher levels in hospitalized individuals. Antibody stability over time was mainly associated with male sex and older age with higher initial levels but more marked decrease.

CONCLUSIONS: The humoral immune response to SARS-CoV-2 infection varies depending on behavioural factors and disease severity, and antibody stability over 15 months was associated with sex and age.

PMID:35996938 | DOI:10.1111/joim.13560

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