Reinfection with SARS-CoV-2 variants: The issues of hybrid immunity efficiency

Current knowledge about vaccine prevention provides the basis for searching a way to unravel the causes of unfavorable disease outcomes and reinfection with COVID-19, both in cases with natural and hybrid immunity observed in patients infected with genetic variants of the SARS-CoV-2 virus. Our aim was study the effect of vaccination on the timing of reinfection with variant strains of the SARS-CoV-2, and to evaluate the differences in Ct values (threshold cycles in PCR test) between primary COVID-19 infection and reinfection cases. The study included 67 patients treated at the St. Petersburg City Hospital No. 40, aged 22-75 years, from April 2020 to August 2023, who were repeatedly infected with the SARS-CoV-2. The criteria for including patients in the study were as follows: a confirmed COVID-19 diagnosis in the initially and repeatedly infected persons with SARS-CoV-2 virus, age from 22 to 75 years, availability of vaccination data between the primary and repeated episodes of the new coronavirus infection. The study did not include pregnant women, patients with mental disorders, cancer, and respiratory infections caused by other respiratory viruses. As a test system for determining Ct values (threshold number of PCR cycles), we used a diagnostic real-time PCR kit for detecting SARS-CoV-2 coronavirus RNA (RealBest RNA SARS-CoV-2, Vector-Best JSC, Russia). Statistical evaluation was carried out using the STATISTICA 13.0 program. The group differences were considered statistically significant at p < 0.05. Analysis of the data obtained revealed a statistically significant difference between (p < 0.05) group A and other groups (B, C, D) in the number of days between the primary and repeated incidence of COVID-19. In the groups A, B, C, D who had a primary viral infection, the Ct levels had no statistically significant differences (p > 0.05). When comparing the results obtained in each group for Ct during primary disease and reinfection with COVID-19, a statistically significant difference was found in group B (p < 0.05). When comparing Ct values during primary and reinfection between group A and other groups, no statistically significant differences were found (p > 0.05). Vaccine prevention is the main strategic task for the near future, but the use of various vaccines for these purposes requires continuous analysis by the medical community.