A pre-print in BioRxiv from a Beijing based biotechnology company company, Sinovac, describes protection of macaque monkeys from infection by SARS-CoV-2 by a vaccine candidate. The candidate is a “killed virus” vaccine prepared by inactivating live virus with beta-Propriolactone, a standard procedure used in inactivate other viruses for use as vaccines. Alum, used in many vaccines, was added to the killed virus preparation to elicit a stronger immune response. To my knowledge this is the first published report of protection of non-human primates by a COVID-19 vaccine candidate.
Preparatory studies of the vaccine candidate were conducted in mice. The vaccine candidate administered day 0 and day 7 elicited strong antibody responses that neutralized all eleven strains of SARS-CoV-2 isolated in China and several European countries. The majority of the antibodies were directed against the part of the spike protein, called the receptor binding domain, necessary for virus infection.
Originally published on Forbes (April 25, 2020)