Anderson, Michaela R.

Background: Despite the availability of effective vaccines and a recent decrease in annual deaths, coronavirus disease-2019 (COVID-19) remains a leading cause of death. Serological studies of anti-nucleocapsid (N) antibody response to infection provide insights into host immunobiology of adaptive immune response, which holds promise for identifying high-risk individuals for adverse acute and chronic COVID-19 outcomes. Hypothesis: Among participants previously infected with SARS-CoV-2, traditional vascular disease risk factors are associated with higher anti-N antibodies while vaccination is associated with lower anti-N antibodies. Methods: Among previously infected participants, anti-N antibodies were measured from dried blood spots collected between February 2021-February 2023 among 1,419 Collaborative Cohort of Cohorts for COVID-19 Research (C4R) participants with prior SARS-CoV-2 infection. We measured anti-N IgG antibodies reported as median fluorescence intensity (MFI) units; reactivity (i.e., seropositivity) was defined based on MFI above a validated threshold. Vascular disease risk factors were assessed via pre-pandemic in-person examination, questionnaires, and medical record review. Multivariable generalized linear models regressed anti-N reactivity (modified Poisson) or LN transformed MFI (linear). Results: Among 1,419 participants with prior infection, mean age (standard deviation) was 65.8(12.1) years, 61% were women, and 42.8% were self-reported from a race/ethnicity minority group. Participant reactivity to nucleocapsid peaked at 69% by 4 months post-infection and waned to only 44% ≥12 months after infection. After multivariable adjustment, higher anti-N antibody response was associated with older age, Hispanic (vs. White) or American Indian (vs. White) race/ethnicity, lower income and education, former smoking, and higher anti-spike antibody levels. Asian race (vs. White) and vaccination ( even after infection ) were associated with lower nucleocapsid reactivity; common cardiometabolic co-morbidities were not associated with anti-N reactivity or levels (Figures 1 and 2). Conclusions: Among participants previously infected with SARS-CoV-2, select sociodemographic and behavioral risk factors were associated with higher anti-N antibody levels while vaccination was associated with lower anti-N antibody levels. The observation that vaccination, even after infection, is related to lower anti-N antibody levels merits further investigation.

Abstract Despite the availability of effective vaccines and a recent decrease in annual deaths, COVID-19 remains a leading cause of death. Serological studies provide insights into host immunobiology of adaptive immune response to infection, which holds promise for identifying high-risk individuals for adverse COVID-19 outcomes. We investigated correlates of anti-nucleocapsid antibody responses following SARS-CoV-2 infection in a US population-based meta-cohort of adults participating in longstanding National Institutes of Health–funded cohort studies. Anti-nucleocapsid antibodies were measured from dried blood spots collected between February 2021 and February 2023. Among 1419 Collaborative Cohort of Cohorts for COVID-19 Research participants with prior SARS-CoV-2 infection, the mean age (standard deviation) was 65.8 (12.1), 61% were women, and 42.8% self-reported membership in a race/ethnicity minority group. The proportion of participants reactive to nucleocapsid peaked at 69% by 4 months after infection and waned to only 44% ≥12 months after infection. Higher anti-nucleocapsid antibody response was associated with older age, Hispanic or American Indian Alaskan Native (vs White) race/ethnicity, lower income, lower education, former smoking, and higher anti-spike antibody levels. Asian race (vs White) and vaccination (even after infection) were associated with lower nucleocapsid reactivity. Neither vaccine manufacturer nor common cardiometabolic comorbidities were not associated with anti-nucleocapsid response. These findings inform the underlying immunobiology of adaptive immune response to infection, as well as the potential utility of anti-nucleocapsid antibody response for clinical practice and COVID-19 serosurveillance.

Background: Adults with cardiovascular co-morbidities and risk factors are at greater risk of severe COVID-19. These same risk factors may also be associated with an attenuated antibody response to COVID-19 vaccines, although studies in diverse, U.S. population-based cohorts have been limited. Methods: The Collaborative Cohort of Cohorts for COVID-19 Research (C4R) conducted a serosurvey for SARS-CoV-2 antibodies via dried blood spot (DBS) in 14 U.S. cohorts. IgG antibodies to SARS-CoV-2 spike subunit 1 (S1) and nucleocapsid (N) were measured from DBS using a semi-quantitative microsphere immunoassay and reported as median fluorescence intensity (MFI). Multivariable adjusted linear models regressed log-transformed anti-S1 MFI on age, sex, race/ethnicity, education attainment, self-reported diabetes, hypertension, cardiovascular disease (CVD), chronic kidney disease, smoking history, body mass index (BMI), asthma, obstructive lung diseases, DBS batch, anti-N MFI, vaccine type, time between vaccine and DBS, and vaccine dose at time of DBS collection. Results are presented as the percent difference in anti-S1 MFI compared with a reference group. Results: There were 6614 vaccinated participants prior to booster regimens and DBS collection (April 2021-July 2022) with 50%, 48%, and 2% of the cohort who received BNT162b2, mRNA-1273, or other vaccines, respectively. The mean (SD) time between vaccination and DBS was 3.8 (1.8) months. Over 10% of the cohort had self-reported a history of diabetes, 55% had hypertension, and 74% had a BMI>25 kg/m 2 . Anti-S1 MFI decreased as the time between vaccine dose and DBS collection increased. Diabetes was associated with a 16.1% lower anti-S1 MFI (95%CI:-22.4,-9.5) whereas neither hypertension (-3.8%;95%CI:-9.3,2.1), nor cardiovascular disease history (-5.3%;95%CI:-16.3,7.4) were associated with anti-S1 MFI. Former and current smoking history were each associated with a lower anti-S1 MFI: (-6.6%;95%CI:-12.1,-0.8) and (-16.1%;95%CI:-24.7,-6.6), respectively. Participants with a BMI 25-29.9 kg/m 2 had a 7.6% higher anti-S1 MFI (95%CI:0.3,15.4) whereas those with a BMI of 30-35 kg/m 2 and >35 kg/m 2 had 6.2% (95%CI:-2.4,15.5) higher and 8.9% lower (95%CI:-17.6,0.7) MFI levels, respectively. Older age and male sex were each associated with a lower anti-S1 MFI and mRNA-1273 vaccine, Asian subgroup, higher anti-N titer, and prior COVID-19 infection were each associated with higher anti-S1 MFI. Chronic kidney disease, education attainment, and lung disease were not associated with anti-S1 MFI. Conclusions: Several traditional cardiovascular disease risk factors were associated with diminished humoral responses to the initial COVID-19 vaccine regimens in a diverse U.S. population-based cohort and may have implications on strategies to improve vaccine responses.