Comparative safety evaluation of intranasal and intramuscular immunisation with Ad26 and Ad5-vectored vaccines to prevent coronavirus infection

Scientific relevance. Intranasal vaccination may dramatically change current approaches to mass immunisation against various infections, shifting the focus from inducing systemic humoral and cellular immune responses to developing mucosal immunity and protective barriers on the mucous membranes, which are entry points for pathogens. Therefore, the safety of switching from intramuscular to intranasal vaccination should be evaluated.Aim. This study aimed to compare the safety of intranasal and intramuscular vaccination using the intermediate results of the phase III VCI-COV-III clinical trial in healthy volunteers.Materials and methods. The evaluation of the safety profile was based on the adverse events and adverse drug reactions (ADRs) documented by investigators in the interim report on the randomised, double-blind clinical trial of the Salnavac intranasal vaccine (InV) and the Gam-COVID-Vac intramuscular vaccine (ImV) against coronavirus infection. The report covered 42 days of observation in 137 healthy volunteers.Results. ADRs were reported for 17/68 (25%) and 30/69 (43.5%) volunteers in the InV group and the ImV group, respectively (p=0.036). The ADRs reported for the InV group were systemic and local, short-term, mostly mild, and generally consistent in incidence and nature with the ADRs typically observed with other nasal products.Conclusions. According to the preliminary data obtained in the clinical trial, the InV demonstrates a high level of safety. Its safety profile is comparable with those of other intranasal and intramuscular vaccines for the prevention of coronavirus infection.