Detection of Replication-Competent Adenoviral Particles in the Vector Vaccines Salnavac® and Gam-Covid-Vac® against the New Coronavirus Infection Covid-19

The 2019–2022 coronavirus pandemic has brought vaccination to the forefront in recent years. As a result, various approaches to vaccine development and their efficacy and safety assessment have emerged. Methods for assessing recombinant vector vaccines using the specific safety criteria (SSC) have been developed in accordance with the FDA requirements. This resulted in the discovery of a link between the ratio of viral particles to cell suspension density and the characteristics of plaques (shape, size, absence of confluent plaques). A vaccine sample was added to a suspension of trypsinized adherent cells. The optimal density for this analysis is 0.6 million/mL for a T-175 culture flask. The study found that Neutral Red was the best dye for intravital cell staining. It enabled the differentiation of dead cells from living cells via cytoplasmic inclusions. The study produced a method with a lower limit of quantification (LLOQ) of 3 PFU/dose that satisfies international regulatory requirements, including those of the Food and Drug Administration (FDA).