The recipients are among a group of 120 healthy volunteers who have registered to receive a dose of the experimental vaccine as part of the first phase of trials, said Vu Dinh Thiem, director of the Center for Clinical Trials under the National Institute of Hygiene and Epidemiology.
The volunteers, aged between 18 and 59, are not suffering from any underlying health conditions, infectious diseases, or allergies, with each person receiving either two doses or a placebo 28 days apart.
They will then be divided into five groups before being given either vaccine doses of one mcg, three mcg, 10 mcg, one mcg with adjuvant supplementation, or alternatively a placebo.
Providing the first phase yields positive results and meets required safety standards, the second phase will then be carried out with a larger sample size.
Earlier, the initial six volunteers received a dose of the experimental vaccine on March 15. Only a few cases witnessed mild side-effects such as a headache or muscle pain around the injection site.
Duong Huu Thai, director of the Institute of Vaccines and Medical Biologicals (IVAC), said the Covivac vaccine has generated antibodies that can protect recipients against variants of the SARS-CoV-2 virus originating from the UK and South Africa.
In addition to Nano Covax, Covivac is the second COVID-19 vaccine produced in Vietnam to reach the clinical trials stage.