The findings were presented by the National Communicable Diseases Committee and the National Vaccine Committee, public health permanent secretary Kiattiphum Wongrajit said.
The results were taken from a study conducted to determine the effectiveness of Sinovac, otherwise known as the CoronaVac vaccine, between April and May when the Alpha variant of the virus was the most prevalent in the country.
The study confirmed that double doses of Sinovac vaccine were effective in reducing infection by the Alpha variant by 71%-91%. The subjects of the study were from high-risk groups in Phuket, Samut Sakhon and Chiang Rai as well as public health workers.
The vaccine was 90.7% effective in the Phuket subjects, 90.5% in those from those in Samut Sakhon, and 82.8% effective in people in Chiang Rai. The results also showed the vaccine was effective in lowering infections among public health workers by 70.9%.
No one died as a result of being inoculated with two doses of Sinovac.
Dr Kiattiphum said data was being gathered for a similar study on the effectiveness of the vaccine against the fast-spreading Delta (Indian) strain.
According to a real-world study, the Sinovac jab also proved to be 95% effective in preventing severe symptoms or even death in people who caught COVID-19 after being vaccinated.
The other vaccine being rolled out in large numbers is manufactured by AstraZeneca, a British-Swedish multinational pharmaceutical and biotechnology company. The government plans to administer about 10 million COVID-19 vaccine doses next month.