Post-vaccination SARS-CoV-2 IgG spike antibody responses among clinical and non-clinical healthcare workers at a tertiary facility in Kenya.

INTRODUCTION: Following the coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, vaccination became the main strategy against disease severity and even death. Healthcare workers were considered high-risk for infection and, thus, were prioritised for vaccination. METHODS: A follow-up to a SARS-CoV-2 seroprevalence study among clinical and non-clinical HCWs at the Aga Khan University Hospital, Nairobi, we assessed how vaccination influenced SARS-CoV-2 anti-spike IgG antibody responses and kinetics. Blood samples were drawn at two points spanning 6 to 18 months post-vaccination, and SARS-CoV-2 spike antibody levels were determined by enzyme-linked immunosorbent assay. RESULTS: Almost all participants, 98% (961/981), received a second vaccine dose, and only 8.5% (83/981) received a third dose. SARS-CoV-2 spike IgG antibodies were detected in 100% (961/961) and 92.7% (707/762) of participants who received two vaccine doses, with the first and second post-vaccine test, respectively, and in 100% (83/83) and 91.4% (64/70) of those who received three vaccine doses at the first and second post-vaccine test, respectively. Seventy-six participants developed mild infections, not requiring hospitalisation even after receiving primary vaccination. Receiving three vaccine doses influenced the anti-spike S/Co at both the first (p<0.001) and second post-vaccination testing (p<0.001). Of those who tested SARS-CoV-2 positive, the anti-spike S/Co ratio was significantly higher than those who were seronegative at the first post-vaccine test (p = 0.001). Side effects were reported by almost half of those who received the first dose, 47.3% (464/981), 28.9% (278/961) and 25.3% (21/83) of those who received the second and third vaccine doses, respectively. DISCUSSION AND CONCLUSION: Following the second dose of primary vaccination, all participants had detectable anti-spike antibodies. The observed mild breakthrough infections may have been due to emerging SARS-CoV-2 variants. Findings suggest that although protective antibodies are induced, vaccination protected against COVID-19 disease severity and not necessarily infection.

SARS-CoV-2 Variants Genotyping and Diagnostic Performance of a 2-Genes Detection Assay.

BACKGROUND: The emergence of the COVID-19 pandemic resulted in the unprecedented expansion of molecular testing technologies. This study aimed at evaluating the performance of the FluoroType® SARS-CoV-2 plus assay for SARS-CoV-2 detection as well as describing the detection of SARS-CoV-2 variants using the FluoroType® SARS-CoV-2 varID Q kit. METHODS: The study utilized 679 archived nasopharyngeal samples. Analytical performance and the diagnostic performance of the FluoroType® SARS-CoV-2 plus assay were determined using 320 samples and reference material. Variants identification on the FluoroType® SARS-CoV-2 varID Q assay was performed on 359 samples. The study was approved by the Aga Khan University Hospital Institutional Review Board. RESULTS: The FluoroType® SARS-CoV-2 plus assay's limit of detection was verified as 1.2 copies/µL. The repeatability SD and %CV were 2.45 and 9.8% while reproducibility had an SD and %CV of 1.39 and 5.68%, respectively, for the RdRP gene. The positive and negative percent agreement were determined to be 99.4% (95% CI; 98.1%-100%) and 99.4% (95% CI; 98.2%-100%) respectively. In the variants identification, samples from the original wave had no mutations identified while 12.3%, 49%, and more than 90% of the samples during the Alpha, Delta, and Omicron waves, respectively, had detectable mutations. CONCLUSIONS: The FluoroType® SARS-CoV-2 plus assay demonstrated analytical performance comparable to the reference method with a diagnostic sensitivity and specificity of >99%. The FluoroType® SARS-CoV-2 varID Q assay achieved rapid detection of circulating variants.