Abstract:
Sputnik-V (Gam-COVID-Vac) is a heterologous, recombinant adenoviral (rAdv) vector-based, COVID-
19 vaccine now used in > 70 countries. Yet there is a shortage of data on this vaccine’s performance in
diverse populations. Here, we performed a prospective cohort study to assess the reactogenicity and
immunologic outcomes of Sputnik-V vaccination in Kazakhstan. COVID-19-free participants (n = 82 at
baseline) were followed at day 21 after Sputnik-V dose 1 (rAd5) and dose 2 (rAd26). Self-reported local
and systemic adverse events were captured using questionnaires. Blood and nasopharyngeal swabs
were collected to perform SARS-CoV-2 diagnostic and immunologic assays. We observed that most
of the reported adverse events were mild-to-moderate injection site or systemic reactions, no severe
or potentially life-threatening conditions were reported, and dose 1 appeared to be more reactogenic
than dose 2. The seroconversion rate was 97% post-dose 1, remaining the same post-dose 2. The
proportion of participants with detectable virus neutralization was 83% post-dose 1, increasing to
98% post-dose 2, with the largest relative increase observed in participants without prior COVID-
19 exposure. Dose 1 boosted nasal S-IgG and S-IgA, while the boosting effect of dose 2 on mucosal
S-IgG, but not S-IgA, was only observed in subjects without prior COVID-19. Systemically, vaccination
reduced serum levels of growth regulated oncogene (GRO), which correlated with an elevation
in blood platelet count. Overall, Sputnik-V dose 1 elicited both blood and mucosal SARS-CoV-2
immunity, while the immune boosting effect of dose 2 was minimal. Thus, adjustments to the current
vaccine dosing regimen are necessary to optimize immunization efficacy and cost-effectiveness. While
Sputnik-V reactogenicity is similar to that of other COVID-19 vaccines, the induced alterations to the
GRO/platelet axis warrant investigation of the vaccine’s effects on systemic immunology.