RESUMO
Measurement of strength and durability of SARS-COV-2 antibody response is important to understand the waning dynamics of immune response to both vaccines and infection. The study aimed to evaluate the level of IgG antibodies against SARS-CoV-2 and their persistence in recovered, naive and vaccinated individuals. We randomly investigate Anti-spike RBD IgG antibody responses in 10,000 individuals, both following infection with SARS-CoV-2 and immunization with SARS-COV-2 adenoviral-vector and killed vaccines. Overall, antibody titres in recovered vaccinated individuals and naive vaccinee persists beyond 20 weeks. The mean levels of anti-spike IgG antibodies were higher in vaccinated participants with prior COVID-19 infections than in individuals without prior infection. Decline for IgG antibodies were faster in vaccinated individuals without previous COVID-19 infection compared to those with previous COVID-19 infection. Vaccination with adenoviral-vector vaccines generates higher antibody titers than for killed virus vaccine. Slightly over half of asymptomatic unvaccinated individuals develops antibody response. Previous COVID-19 infection elicited robust and sustained levels of SARS-CoV-2 antibodies in vaccinated individuals. A single dose of the vaccine is likely to provide greater protection against SARS-CoV-2 infection in individuals with prior SARS-CoV-2 infection, than in SARS-CoV-2-naive individuals. This study also underlines that asymptomatic infection equally generates antibodies as symptomatic infection. Those vaccinated with inactivated vaccine may require more frequent boosters than those vaccinated with an adenoviral vaccine. These findings are important for formulating public health vaccination strategies during COVID-19 pandemic. ImportanceMeasurement of strength and durability of SARS-COV-2 antibody response is important to understand the waning dynamics of immune response to both vaccines and infection. We randomly surveyed 10,000 people for SARS-COV-2 antibodies. One vaccine dose with prior infection generated stronger immune response than two vaccine doses. Overall, antibody titres in recovered vaccinated individuals and naive vaccinee persists beyond 20 weeks. Vaccination with adenoviral-vector vaccines generates higher antibody titers than for killed virus vaccine slightly over half of asymptomatic unvaccinated individuals develops antibody response. This study emphasise on the benefit of vaccination in inducing strong immune response. These findings are important for formulating public health vaccination strategies during COVID-19 pandemic.
RESUMO
There is a great demand for more rapid tests for SARS-COV-2 detection to reduce waiting time, boost public health strategies for combating disease, decrease costs, and prevent overwhelming laboratory capacities. This study was conducted to assess the performance of 10 lateral flow device viral antigen immunoassays for the detection of SARS-CoV-2 in nasopharyngeal swab specimens. We analyzed 231 nasopharyngeal samples collected from October 2020-December 2020, from suspected COVID-19 cases and contacts of positive cases at Biotechnology Research Center laboratories, Tripoli, Libya. The performance of 10 COVID-19 Antigen (Ag) rapid test devices for the detection of SARS-CoV-2 antigen was compared to RT-qPCR. In this study 161 cases had symptoms consistent with COVID-19. The mean duration from symptom onset was 6.6 {+/-}4.3 days. The median cycle threshold (Ct) of positive samples was 25. Among the 108 positive samples detected by RT-qPCR, the COVID-19 antigen (Ag) tests detected 83 cases correctly. All rapid Ag test devices used in this study showed 100% specificity. While tests from 6 manufacturers had an overall sensitivity range from 75-100%, the remaining 4 tests had sensitivity of 50-71.43%. Sensitivity during the first 6 days of symptoms and in samples with high viral loads (Ct<25), was 100% in all but 2 of the test platforms. False negative samples had a median Ct of 34 and an average duration of onset of symptoms of 11.3 days (range=5-20 days). Antigen test diagnosis has high sensitivity and specificity in early disease when patients present less than 7 days of symptom onset. Patients are encouraged to test as soon as they get COVID-19 related symptoms within 1 week and to seek medical advice within 24 hrs. if they develop disturbed smell/taste. The use of rapid antigen tests is important for controlling COVID-19 pandemic and reducing burden on molecular diagnostic laboratories.
