Purpose: To explore the influencing factors to predict the negative nucleic acid conversion time and ORF1ab gene CT value changes in patients with asymptomatic and mild COVID-19.
Patients and Methods: A total of 73,456 patients with asymptomatic and mild COVID-19 admitted to the Mobile Cabin Hospital in Shanghai from April 3 to April 23, 2022 were selected as the research objects. Epidemiological, clinical, and laboratory data were collected. Correlation analysis was performed.
Results: In patients < 18 years old and ≥ 65 years old, COVID-19 vaccine can shorten the negative nucleic acid conversion time, which is reflected in the lower median or 75% quantile (P< 0.001, P< 0.05). In patients with underlying diseases, the negative nucleic acid conversion time of booster vaccination and complete vaccination was lower than that of non-vaccinated group (P< 0.001, P< 0.05). In patients ≤ 18 years of age or > 65 years of age, patients with comorbidity and patients with symptoms, compared with patients 18– 65 years of age, patients without comorbidity and patients without symptoms, there was a greater difference in the rate of rise of CT values between vaccinated and unvaccinated patients (P< 0.05).
Conclusion: The time of nucleic acid conversion to negative in patients with asymptomatic and mild COVID-19 is affected by age, comorbidity, and first nucleic acid CT value. Vaccination could shorten the negative nucleic acid conversion time of the older population, those with complications or symptoms. The vaccination of older patients does not increase the risk of symptoms.

Keywords: COVID-19, nucleic acid detection, CT value, vaccine, older population