The first phase of human trials of Thailand’s vaccine candidate, jointly developed domestically by the Government Pharmaceutical Organization (GPO) and the Tropical Medicine Faculty of Mahidol University, has produced a promising human response in the volunteers, according to Prof. Dr. Pannee Pitisutthitham, acting head of the vaccine centre of the faculty.

Speaking via the Mahidol Channel, Professor Pannee said the vaccine candidate, called HXP-GPOVac, which is an inactivated virus type vaccine, was developed from a viral precursor, obtained from PATH, a global health organisation based in the United States, and was used in first phase of human trials among volunteers in March.

All 210 volunteers in the trials are in good health, free from Hepatitis B and C and are not suffering from an immune deficiency. The volunteers were separated into six groups, each was injected with differing dosages of vaccine, in order to assess the appropriate dosage to be used once approved. Some of the volunteers were given placebo instead, as a control measure.

Professor Pannee said that initial laboratory test results show an impressive immune response, which are similar to the results from tests conducted abroad.

In the next phase, scheduled to begin in August, 250 volunteers will be used to determine the best two of the five formulae of the vaccine candidate.

The third phase will involve 1,000-10,000 volunteers and the two chosen vaccine formulae will be administered, she added.

The Mahidol University’s vaccine candidate modifies the avian Newcastle disease virus with a COVID-19 spike protein and it is replicated using egg-based technology, according to the GPO.

Another homegrown vaccine is being developed by Chulalongkorn University’s Chula Vaccine Research Centre. Human trials started in June.

The vaccine candidate, ChulaCov19, has shown promising results in unpublished preclinical studies in mice and primates, according to Dr. Kiat Ruxrungtham, the vaccine’s designer.

The phase 1 trials were to figure out the appropriate dose for generating a good immune response. Once this milestone is passed, the second phase trials will follow, testing the consistency of response in a few hundred volunteers and assessing the safety of the vaccine in some 5,000 individuals.  To test efficacy, tens of thousands of individuals will be needed.