Initial results showing all 556 volunteers, who got injected with the 25, 50 and 75 microgram vaccine doses in groups, produced the same level of immunogenicity.

Researchers said they would use the result produced by the lowest 25 microgram dosage group as the proposed optimal dose for use in Nanocovax’s third phase of human trials, expected to commence May 5 until end of June, involving over 1,000 volunteers.

Official results for the second phase are expected to be reported to the Ministry of Health on Tuesday. On completion of human trials, Nanocovax is expected to seek emergency approval for community distribution.

Vietnam is currently developing four domestic Covid-19 vaccines: Nanocovax by Nanogen, Covivac by the Institute of Vaccines and Medical Biologicals (IVAC), and two others by the Vaccine and Biological Production Company No. 1 (Vabiotech) and the Center for Research and Production of Vaccines and Biologicals.

Covivac is expected to finish its first phase of human trials involving 120 volunteers on May 15 and begin the second in June.

Besides domestic vaccine sources, Vietnam has already deployed a Covid-19 vaccine produced by British-Swedish firm AstraZeneca in its ongoing mass Covid-19 inoculation program. So far, over 209,000 have received the jab, mainly frontline workers in the Covid-19 fight.

Vietnam aims to secure 150 million Covid-19 vaccine doses to cover 70 percent of its population by next year.