Heterologous vaccination regimens with self-amplifying RNA and Adenoviral COVID vaccines induce superior immune responses than single dose vaccine regimens in mice
Spencer AJ., McKay PF., Belij-Rammerstorfer S., Ulaszewska M., Bissett CD., Hu K., Samnuan K., Sharpe HR., Wright D., Gilbride C., Truby A., Allen ER., Gilbert SC., Shattock RJ., Lambe T.
<jats:p>Several vaccines have demonstrated efficacy against SARS-CoV-2 mediated disease, yet there is limited data on the immune response induced by heterologous vaccination regimens using alternate vaccine modalities. Here, we present a detailed description of the immune response, in mice, following vaccination with a self-amplifying RNA (saRNA) vaccine and an adenoviral vectored vaccine (ChAdOx1 nCoV-19/AZD1222) against SARS-CoV-2. We demonstrate that antibody responses are higher in two dose heterologous vaccination regimens than single dose regimens, with high titre neutralising antibodies induced. Importantly, the cellular immune response after a heterologous regimen is dominated by cytotoxic T cells and Th1+ CD4 T cells which is superior to the response induced in homologous vaccination regimens in mice.</jats:p>