Immunogenicity and reactogenicity of heterologous immunization schedules using Sputnik V, ChAdOx1-S, BBIBP-CorV, Ad5-nCoV and mRNA-1273

Heterologous vaccination regimens against COVID-19 provide a rational strategy to rapidly increase the rate of coverage in many regions of the world. In Argentina, a number of different
vaccine platforms are being used, including the non-replicating adenovirus vaccines ChAdOx1-S, Ad5-nCoV, and Sputnik V; the mRNA vaccines BNT162b2 and mRNA-1273; and the
inactivated SARS-CoV-2 vaccine BBIBP-CorV. Although data are available about mRNA and ChAdOx1 vaccines combination, very limited information has been reported combining these
platforms with other vaccines widely used in developing countries, such as BBIBP-CorV and Sputnik V. We assessed the immunogenicity and reactogenicity of 15 vaccine combinations in
a cohort of 1314 participants. The antibody response was evaluated by determining IgG antibodies anti-spike and serum neutralizing titers. We observed that a number of heterologous
vaccine combinations are equivalent or superior to the homologous schemes. For all the cohorts analyzed, the highest antibody response was induced by mRNA-1273 as second dose. The
results also highlight the benefit of using heterologous schedules in individuals primed with BBIBP-CorV. No serious adverse events were detected in any of the schedules analyzed. Our
observations provide rational support for the use of different vaccine combinations with the aim of achieving wide vaccine coverage in the shortest possible time.