The COVID-19 pandemic posed major challenges to the global healthcare system. Early detection of infection and effective population immunization were considered key factors in limiting the spread of the disease. The treatment of this coronavirus infection, laboratory diagnostics, epidemiology, and prevention became the focus of scientific activity for a number of researchers. For example, in countries such as China, Russia, the United Kingdom, Germany, India, as well as in Uzbekistan, several scientists are actively conducting effective scientific research on disease prevention. This study examined the significance of the PCR diagnostic method and the immunological effectiveness of a heterologous (mixed) vaccination strategy. The study analyzed data from 2021–2022, focusing on immune responses after vaccination across different age groups. The results showed that heterologous vaccination is associated with a higher antibody level.The results obtained are of great importance for improving epidemiological control.