The Impact of Vaccination on RT-PCR Cycle Threshold Values for COVID-19: Insights for Future Pandemic Preparedness

Amid the COVID-19 surge, effective management hinges on precise diagnostic techniques, particularly through the comparison of results among vaccinated and unvaccinated individuals. This research seeks to assess clinical evaluations, Rapid Diagnostic Tests (RDT), and Reverse Transcription Polymerase Chain Reaction (RT-PCR) findings, with a specific focus on the correlation between vaccination status and RT-PCR Cycle threshold (Ct) values. A total of 453 suspected COVID-19 cases were included in the study. Detailed information on clinical symptoms, RDT, and RT-PCR results was meticulously collected. Nasopharyngeal swabs were collected for both RDT and RTPCR examinations following established procedures. While RDTs were carried out on-site, RT-PCR tests were performed at the Ethiopian Public Health Institute (EPHI) genomics laboratory. Data analysis involved descriptive statistics, cross-tabulation, and Chi-Square tests to reveal connections between diagnostic outcomes and vaccination status, particularly focusing on Ct values in RT-PCR tests. RDT findings showed 34.0% negative and 65.8% positive results, while RT-PCR indicated 35.8% negative and 64.2% positive results. Discrepancies between RDT and RTPCR results highlighted the importance of comprehensive testing protocols. Further investigation found no significant link between vaccination status and viral load, as indicated by Ct values. Among RT-PCR positive cases, 49.8% had been vaccinated, underscoring the complexities of interpreting test results in vaccinated populations. Analysis of viral load in relation to vaccination status revealed that neither the first nor second dose of the COVID-19 vaccine had a notable impact on Ct values, suggesting that vaccination status alone may not greatly affect viral load dynamics in infected individuals. This underscores the substantial differences between RDT and RT-PCR outcomes, emphasizing the necessity of holistic testing approaches. Additionally, findings indicate that vaccination status does not markedly impact RT-PCR Ct values, underscoring the complexity of interpreting diagnostic results in the context of vaccination, particularly concerning breakthrough infections and false positives. Keywords Clinical symptoms; COVID-19; Diagnostics; Test result; RDT; RT-PCR