Lancet (London, England) Snape, M D 2021, ' Safety and immunogenicity of heterologous versus homologous prime-boost schedules with an adenoviral vectored and mRNA COVID-19 vaccine (Com-COV) : a single-blind, randomised, non-inferiority trial ', Lancet, vol. 398, no. 10303, pp. 856-869 . https://doi.org/10.1016/S0140-6736(21)01694-9