Introduction: Even though over a year has passed since the coronavirus 2019 (COVID-19) outbreak, our information regarding certain aspects of the disease, such as post-infection immunity is still very limited. This study aimed to evaluate post-infection protection and COVID-19 features among healthcare workers (HCWs), during three subsequent surges.Method: The study population consisted of all HCWs in either public or private hospitals in Fars province, Southern Iran from 20 April 2020 up to 20th February 2021. We calculated the rate of infection as the number of individuals with positive PCR tests divided by the cumulative number of person-days at risk. Poisson regression was utilized to calculate the adjusted rate ratio and estimated protection. Results: During the study period, a total of 30,546 PCR tests were performed among HCWs, of which 13,749 HCWs were positive. Among a total of 141 diagnosed cases who experienced a second episode of COVID-19, 44 (31.2%) cases of reactivation and relapse, and 97 (68.8% of infected and 1.81% of total HCWs) cases of reinfection was observed. The daily rate of infection was 4.72 for previously infected HCWs, while 2.20 for HCWs without previous infection. The estimated protection against repeat infection after a previous SARS-CoV-2 infection was 94.8% (95% CI: 93.6-95.7).Conclusion: Re-positivity, relapse, and reinfection of SARS-CoV-2 are quite rare in the population of HCWs. Also, after a first episode of infection, estimated protection of 94.8% was achieved against repeat infections.
Currently, many efforts have been made against Coronavirus 2019 (COVID-19) as a global outbreak. So far, several vaccines with different platforms are available in the market. Various variants of the SAR-CoV-2 virus have evolved over time. The emergence of variant of Concerns (VOCs), especially new subvariants of BA.4 and BA.5, which can neutralize the effect of current vaccines. Therefore, in this study, we used the bioinformatics approach to design an effective novel candidate vaccine against Variant of Concern (VOC) of COVID-19 (B.1.1.529 or Omicron) based on Spike (S1_ receptor-binding domain or RBD) protein sequence. Here, we employed bioinformatics tools to design a novel fusion protein construct containing the mutant sequence of Omicron Spike_S1_RBD region (as target antigen) and amino acid sequence of human β-defensin-2 as adjuvant molecule. Then, the mutant RBD and β-defensin-2 amino acid sequences were joined together by the suitable linker and novel vaccine construct was designed. Subsequently, immunological and structural evaluations such as antigenicity, allergenicity, physicochemical properties, 3D modeling, molecular docking, and fast flexibility simulations, immune responses simulation as well as in silico cloning were performed. Immunological and structural computational data showed that designed vaccine construct potentially has proper capacity for inducing immune responses against BA.4/5 subvariant of Omicron. Based on the preliminary results, in vitro and in vivo experiments are required for validation in the future.
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