Journal of Infectious Diseases and Diagnosis

Abstract

The Effect of COVID-19 Vaccination Status on RT-PCR Ct Values: A Comprehensive Study

Abebe M Aga*, Demise Mulugeta, Jemal Mohammed, Anberber Alemu, Yewenshet Tesera, Dereje Nigussei, Bedasa Gidisa, Jaleta Bulti, Frehiwot Mulugeta, Atsbeha Gebreegziabxier, Gemechu Tadesse

During COVID-19 pandemic, efficient management relies on accurate diagnostic methods, especially by comparing outcomes for vaccinated and unvaccinated individuals, is essential. This study aims to evaluate clinical assessments, Rapid Diagnostic Tests (RDT), and Reverse Transcription Polymerase Chain Reaction (RT-PCR) outcomes, focusing particularly on the relationship between vaccination status and RT-PCR cycle threshold (Ct) values. The study involved 453 suspected COVID-19 cases from Addis Ababa, Ethiopia. Data on clinical symptoms, RDT and RT-PCR outcomes were collected. Nasopharyngeal swabs were taken for both RDT and RT-PCR, following standard protocols. RDTs were conducted on-site, while RT-PCR tests were performed at the Ethiopian Public Health Institute (EPHI) genomics laboratory. Data analysis included descriptive statistics, cross-tabulation and chi-square tests to explore associations between diagnostic outcomes and vaccination status, with particular attention to Ct values in RT-PCR tests. RDT results showed 34.0% negative and 65.8% positive outcomes, while RT-PCR indicated 35.8% negative and 64.2% positive outcomes. Discrepancies between RDT and RT-PCR results underscore the importance of comprehensive testing strategies. Further analysis revealed no significant association between vaccination status and viral load, as indicated by Ct values. Among the RT-PCR positive cases, 49.8% were vaccinated, demonstrating the complexity of interpreting test outcomes in vaccinated populations. The examination of viral load relative to vaccination status showed that receiving either the first or second dose of the COVID-19 vaccine did not significantly alter Ct values, suggesting that vaccination status alone may not significantly impact viral load dynamics among infected individuals. The study reveals significant disparities between RDT and RT-PCR results, underscoring the necessity of comprehensive testing. Additionally, findings indicate that vaccination status does not significantly affect RT-PCR Ct values, highlighting the complexity of interpreting diagnostic outcomes in the context of vaccination, particularly regarding breakthrough infections and false positives.

Published Date: 2025-08-14; Received Date: 2024-05-22