PROS1 and COVID-19: The neutralizing antibody titers from NHP against live SARS-CoV-2 after the 2nd immunization for S-Trimer with both adjuvants appeared to be similar to that of full-length S protein made from insect cells30, but 1–2 orders of magnitude higher than those from similar studies using other vaccine approaches such as mRNA, DNA, inactivated SARS-CoV-2, RBD derived subunit and other viral vector based COVID-19 vaccine candidates31,40–42.