This study aimed to evaluate the performance characteristics of a rapid antigen test developed to detect SARS-CoV-2 (COVID-19), influenza A virus (IAV), and influenza B virus (IBV) (flu) compared with those of the real-time reverse transcription-polymerase chain reaction (rRT-PCR) method. One hundred SARS-CoV-2, one hundred IAV, and twenty-four IBV patients whose diagnoses were confirmed by clinical and laboratory methods were included in the patient group. Seventy-six patients, who were negative for all respiratory tract viruses, were included as the control group. The Panbio™ COVID-19/Flu A&B Rapid Panel test kit was used in the assays. The sensitivity values of the kit were 97.5%, 97.9%, and 33.33% for SARS-CoV-2, IAV, and IBV, respectively, in samples with a viral load below 20 Ct values. The sensitivity values of the kit were 16.7%, 36.5%, and 11.11% for SARS-CoV-2, IAV, and IBV, respectively, in samples with a viral load above 20 Ct. The kit’s specificity was 100%. In conclusion, this kit demonstrated high sensitivity to SARS-CoV-2 and IAV for viral loads below 20 Ct values, but the sensitivity values were not compatible with PCR positivity for lower viral loads over 20 Ct values. Rapid antigen tests may be preferred as a routine screening tool in communal environments, especially in symptomatic individuals, when diagnosing SARS-CoV-2, IAV, and IBV with high caution.

Following the emergence of severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) and using only PCR for diagnosis, antibody tests have been rapidly developed by various commercial companies. There are differences between the sensitivity and specificity of these tests due to the usage of different viral target proteins and antibody subclasses. In order to evaluate the diagnostic use of these tests, we aimed to examine the diagnostic performance, especially sensitivity and specificity, of SARS-CoV-2 IgM, IgA and IgG tests of various companies (Abbott, Roche, Euroimmun, Dia.Pro, Anshlabs, Vircell, UnScience and RedCell), which have different principles (ECLIA/CLIA, EIA, LFA). Current (n= 180) and past (n= 180) COVID-19 patients with clinical and molecular diagnosis of COVID-19 admitted to Istanbul University-Cerrahpaşa, Cerrahpaşa Faculty of Medicine Hospital, Pandemic Polyclinic with suspected COVID-19 infection, were included in our study. The patients admitted within the first 3 weeks after the onset of symptoms were included in the current patient group, and those admitted at the third and after the third week were included in the past patient group. Serum samples (n= 180) obtained from Istanbul Sisli Hamidiye Etfal Training and Research Hospital, Blood Center between April and June 2018 before the COVID-19 pandemic were included in the study as a control group. All the tests included in our study were studied with the recommendations of the manufacturer companies. Between the IgG detection tests with different principles in patients with past COVID-19, the sensitivity and specificity values of the most effective tests were; 86.7%/99.4% (Abbott), 86.1%/98.9% (Dia.Pro), 91.3%/95% (RedCell). Between the IgM detection tests with different principles in current COVID-19 patients, the sensitivity and specificity values were; 67.8%/99.4% (Abbott), 68.9%/98.6% (Vircell), 50%/97.5% (RedCell). Abbott IgM with a kappa coefficient of 0.67 and Vircell IgM + IgA test with a kappa coefficient of 0.65 showed the best fit in patients with current COVID-19 infection. In patients with past COVID-19, Abbott IgG with 0.86 kappa coefficient and Dia.Pro IgG test with 0.85 kappa coefficient showed the best match. Due to the low sensitivity of IgM detection antibody tests, they should not be preferred instead of real-time reverse transcriptase polymerase chain reaction in routine diagnosis. IgG detection tests may be preferred to detect the antibody response and the titers in people who have had COVID-19 for population seroprevalence and especially therapeutic immune plasma production. However, it is thought that the combined use of both ECLIA/CLIA-based and EIA/ELISA-based tests together may be more effective in routine use for SARS-CoV-2 IgG tests.

Numerous vaccines have been generated to decrease the morbidity and mortality of COVID-19. This study aims to evaluate the immunogenicity of the heterologous boosts by BioNTech against homologous boosts by CoronaVac at three-month intervals in two health care worker (HCW) cohorts, with or without prior COVID-19, for one year post-vaccination. This is a prospective cohort study in which the humoral responses of 386 HCWs were followed-up longitudinally in six main groups according to their previous COVID-19 exposure and vaccination status. Anti-SARS-CoV-2 spike-RBD total antibody levels were measured and SARS-CoV-2 neutralization antibody (NAbs) responses against the ancestral Wuhan and the Omicron variant were evaluated comparatively using international standard serum for Wuhan and Omicron, as well as with the aid of a conversion tool. The anti-SARS-CoV-2 spike-RBD total Ab and Nab difference between with and without prior COVID-19, three months after two-dose primary vaccination with CoronaVac, was statistically significant (p = 0.001). In the subsequent follow-ups, this difference was not observed between the groups. Those previously infected (PI) and non-previously infected (NPI) groups receiving BioNTech as the third dose had higher anti-SARS-CoV-2 spike total Ab levels (14.2-fold and 17.4-fold, respectively, p = 0.001) and Nab responses (against Wuhan and Omicron) than those receiving CoronaVac. Ab responses after booster vaccination decreased significantly in all groups at the ninth-month follow-up (p < 0.05); however, Abs were still higher in all booster received groups than that in the primary vaccination. Abs were above the protective level at the twelfth-month measurement in the entire of the second BioNTech received group as the fourth dose of vaccination. In the one-year follow-up period, the increased incidence of COVID-19 in the groups vaccinated with two or three doses of CoronaVac compared with the groups vaccinated with BioNTech as a booster suggested that continuing the heterologous CoronaVac/BioNTech vaccination, revised according to current SARS-CoV-2 variants and with at least a six-month interval booster would be an effective and safe strategy for protection against COVID-19, particularly in health care workers.