Background: Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants, poses an ongoing global threat, particularly in low-immunization coverage regions. Thus, rapid, accurate, and easy-to-perform diagnostic methods are in urgent demand to halt the spread of the virus. Objective: We aimed to validate the clinical performance of the FastProof™ 30 min-TTR SARS-CoV-2 reverse transcription loop-mediated isothermal amplification (RT-LAMP) method using leftover ribonucleic acid (RNA) samples extracted from 315 nasopharyngeal swabs. The sensitivity and specificity of RT-LAMP were determined in comparison with RT-PCR. Result: Out of 315 nasopharyngeal swabs, viral RNA was detected in 154 (48.9%) samples by RT-PCR assay. Compared with RT-PCR, overall sensitivity and specificity of RT-LAMP were 81.82% (95% CI: 74.81–87.57) and 100% (95% CI: 97.73–100), respectively. A 100% positivity rate was achieved in samples with cycle threshold (Ct) <31 for RT-PCR targeting the ORF1ab gene. However, samples with Ct >31 accounted for false-negative results by RT-LAMP in 28 samples. Conclusion: RT-LAMP reliably detected viral RNA with high sensitivity and specificity and has potential application for mass screening of patients with acute COVID-19 infection, when viral load is high.

Two primary vaccines for coronavirus disease 2019 (COVID-19) have been rolled out in the mass vaccination campaign that started simultaneously with the spread of the delta variant. To explore the vaccines’ effect on reducing viral load and disease severity, we conducted a retrospective cohort study in Thai patients aged ≥ 18 years who were confirmed COVID-19 positive by RT-PCR. Compared to unvaccinated patients, Ct values and the number of severe cases among vaccine regimens were analyzed. Ct values of vaccinated patients were not significantly different from unvaccinated patients, despite an increase of Ct values in a booster dose. The adjusted odd ratio for prevention of delta-related severe diseases was 0.47, 95% CI: 0.30–0.76 and 0.06, 95% CI: 0.01–0.45 after receiving one dose and two doses, respectively. No severe illness was found in booster-vaccinated individuals. Focusing on the vaccine types, one dose of ChAdOx1 nCoV-19 gave significant protection, whereas one dose of CoronaVac did not (0.49, 95% CI: 0.30–0.79, p = 0.003 vs. 0.28, 95% CI: 0.04–2.16, p = 0.223). Two-dose vaccination showed robust protective effects in all subpopulations regardless of vaccine type. Vaccinations with two primary vaccines could not reduce viral load in patients with COVID-19, but could prevent severe illness.

Background Two primary vaccines for coronavirus disease 2019 (COVID-19) have been rolled out in the mass vaccination campaign that started simultaneously with the spread of the delta variant. This study aimed to explore vaccines’ effect on reducing infectiousness and disease severity. Methods This retrospective cohort study was conducted in Thai patients aged ≥ 18 years who received one and two doses of either CoronaVac or ChAdOx1 nCoV-19 and a booster vaccine and confirmed COVID-19 positive by reverse-transcriptase polymerase chain reaction. To determine the effect of vaccines on infectiousness and occurrence of severe COVID-19-related outcomes, the Ct values and number of severe cases were compared between vaccinated and unvaccinated people, among vaccine regimens. Results No difference in Ct values was found between the vaccinated and unvaccinated groups. To reduce the occurrence of severe illness, the vaccine effectiveness (VE) of a vaccine booster and two-dose CoranaVac provided 100% protection, followed by two-dose ChAdOx1 nCoV-19 (84.7%, 95% CI 18.2–98.0), whereas one-dose regimen of either CoronaVac or ChAdOx1 nCoV-19 had VE of < 71.6%. Conclusion Vaccinations with two primary vaccines could not reduce viral load in patients with COVID-19, but could prevent severe illness.