Tags COVID-19 variant vaccine First COVID-19 variant vaccine AZD2816 Phase II/III trial participants vaccinated Thursday, Jul 08, 2021 Over 2,250 adults will participate in a phase II/III trial for the new COVID-19 variant vaccine AstraZeneca’s AZD2816 to assess safety and immunogenicity against the SARS-CoV-2 virus, the company reported.