Date of Award

2022

Embargo Period

8-1-2024

Document Type

Thesis - MUSC Only

Degree Name

Master of Science (MS)

Department

Public Health Sciences

College

College of Graduate Studies

First Advisor

Jeffrey E. Korte

Second Advisor

Cassandra D. Salgado

Third Advisor

Lisa L. Steed

Fourth Advisor

Michael G. Schmidt

Fifth Advisor

Mulugeta G. Gebregziabher

Abstract

With the introduction of vaccines and later vaccine mandates at an academic health system after the COVID-19 pandemic, opportunities arose for assessing not only vaccine effectiveness but also the hypothesis that vaccination had some detectable benefit for even those persons experiencing vaccine breakthrough infections. By describing the symptom characteristics, illness duration and viral burden among students, faculty, staff and care team members (SFSCTMs), the hypothesis that vaccination results in COVID-19 disease attenuation was explored. REDCap (v11.2.1) was used as a contact tracing survey to SFSCTMs diagnosed with COVID-19. A retrospective cohort study of SFSCTMs at MUSC Health who completed their survey joined with laboratory data was conducted. Case-population methods were used to estimate vaccine effectiveness for the endpoint of symptomatic COVID-19. Linear and logistic regression methods were used to assess the independent contribution of age, race, medical co-morbidities, viral lineage, and vaccination status on SARS-CoV-2 viral burden and COVID-19 illness severity as measured by total symptoms score, illness duration, and the categorical outcome of prostration. 5,722 SFSCTMs acquired COVID-19 and 3,296, 1859, and 1067 had data sufficient for analysis of illness severity, viral burden, and illness duration, respectively between 2/28/2020 and 3/23/2022. Re-infections (n=189) were excluded from analyses. Vaccine effectiveness for 1-dose vaccinated, 2-dose vaccinated, and 3-dose vaccinated SFSCTMs was estimated at 67.3% (95% CI, 62.5, 71.5), 44.8% (95% CI, 43.9, 45.7), and 88.0% (95% CI, 87.5, 88.4%), respectively. Vaccination status was not significantly associated with a change in total symptoms score, although male gender and black race were each associated with ~1 fewer symptoms on a 17-point scale while self-reported immune compromise and lung disease were each independently associated with +1 symptoms on the same scale in linear regression models. In contrast, logistic regression models identified vaccination status with 3 or more doses (p=.006), black race (p<.0001), male gender(p<.0001), and pregnancy(p=.007) as significantly associated with decreased odds of prostration in contrast to self-reported lung disease(p=.003), which increased odds of prostration from COVID-19; there was no independent signficant effect of viral lineage observed. Vaccination was found to be independently associated with lower illness duration compared to unvaccinated SFSCTM respondents in a dose-dependent fashion (1.2, 1.5 days shorter illness duration for fully vaccinated and fully vaccinated+boosted respondents compared to unvaccinated, respectively) for the endpoint of illness duration when controlling for the effect of delta lineage infections, which increased illness duration by 2.4 days compared to non-VOC/VOI infections, male gender (1.3 days shorted compared to females), and age; co-morbidities were not significant in this model. While viral load data was not amenable to linear regression modeling, 3-dose vaccinated SFSCTMs were significantly associated with higher median Cn/Ct values (lower viral burdens) compared to unvaccinated respondents, despite a significant association of delta variant infections with higher viral burdens. The cumulative effect of vaccination appears to indicate that (1) vaccines remain remarkably effective for the endpoint of COVID-19 infection preventions and (2) even for those experiencing vaccine breakthrough infections, COVID-19 illness severity and duration is attenuated, even when controlling for the impact of other significant factors such as viral lineage, age, and race.

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Available for download on Thursday, August 01, 2024

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