As Thailand aims to vaccinate 70 percent of its population by September, vaccination remains an important task and the question is the supply, experts say.

"The global COVID-19 pandemic has brought many countries together in the spirit of cooperation towards a common goal, which is to rapidly develop and deploy effective vaccines," said Yong Poovorawan, head of the Center of Excellence in Clinical Virology at the Faculty of Medicine, Chulalongkorn University in Bangkok.

"As in many countries around the world, vaccination will play a very important part in limiting the COVID-19 transmission Thailand," Yong told China Daily.

A study by the Center of Excellence in Clinical Virology found that 99.49 percent of the people receiving CoronaVac had developed antibody responses four weeks after their second injection, local media Bangkok Post reported on May 16. The number was only 65.9 percent three weeks after the first jab.

"Two doses of CoronaVac were immunogenic in vaccinated volunteers," said Yong, noting the result is consistent with the preliminary findings previously reported in the medical journal Lancet Infectious Diseases last year, which found that the Chinese inactivated COVID-19 vaccine can induce a quick immune response.

Thailand's Health Minister Anutin Charnvirakul, said on May 19 that the country is aiming to administer one shot of a coronavirus vaccine to 70 percent of its population by September, according to local media, as it seeks to accelerate the protection for more people amid its worst outbreak so far.

Thailand reported 3,394 new COVID-19 cases on May 19, raising the total caseload to 116,949, according to the Center for COVID-19 Situation Administration. The number was more than quadrupling from the start of April, when the latest outbreak began to spread from Bangkok.

Though Thailand would like to vaccinate as many people as possible and as soon as possible, Yong said the availability of the COVID-19 vaccines remains an issue.

Only 1.59 million of Thailand's 70 million people have received at least one vaccine dose as of May 18, according to Oxford-linked tracker Our World in Data. Most of them were using the vaccine developed by Chinese biopharmaceutical producer Sinovac Biotech, while Thailand has also ordered vaccines from other international vaccine manufacturers such as Pfizer and BioNTech.

The Chinese embassy in Thailand said China donated a new batch of 500,000 doses of Sinovac COVID-19 vaccines to Thailand on May 17.

A total of 4 million doses China-made COVID-19 vaccines ordered by Thailand have also been delivered as of May 17.

An additional 1.5 million doses will arrive in Bangkok within May, Chinese embassy official Yang Xin said.

Tang Zhimin, director of China ASEAN Studies at the Bangkok-based Panyapiwat Institute of Management (PIM), said the supply from China is "substantial and timely" for the ambitious vaccination plan proposed by the Thai government.

"Thailand was the first ASEAN country to import Sinovac on a commercial basis," Tang told China Daily. "The support from China to Thailand during the pandemic contributes to bilateral ties."

The Association of Southeast Asian Nations, or ASEAN, is a ten-nation bloc that includes Thailand.

Yet Yong from Chulalongkorn University said people's concern over vaccine safety and effectiveness is another issue for accelerating the vaccine rollout within the country.

"It would be very helpful for China to encourage Sinovac to pursue transparency and timeliness in sharing their ongoing research results in CoronaVac, which should help people make better informed decisions and address the concerns of vaccine hesitancy," said Yong.

"China can be confident to let the science and evidence speak for themselves," said Lye Liang Fook, senior fellow at the ISEAS-Yusof Ishak Institute in Singapore.

Lye said China's supply of vaccines to Southeast Asia enables the regional countries to have viable alternatives and help reduce their overdependence on vaccines provided by any one particular company or country.

In South America, an updated study showed that the CoronaVac vaccine by Sinovac is 65.3 percent efficacious in preventing COVID-19, Xinhua reported on May 17, citing Chile's Health Ministry.

Despite the COVID-19 variants in circulation, Rafael Araos, an advisor to the Underseretariat of Public Health, said "the vaccine is performing adequately".

Noting the level of efficacy may vary based on where and how the study is conducted, as well as the existence of different variants, Singapore-based researcher Henry Chan said people should not focus on the percentage of how efficacious a vaccine can be since what is important is that it can reduce the symptoms.

"(The donation by China) is a very good move because they (Thailand) are experiencing a very bad resurgence and everybody realized that now…vaccine is the best you can do," said Chan, who is also visiting senior research fellow at the Cambodian Institute for Cooperation and Peace, a think tank in Phnom Penh.

"People will remember who helps them and who doesn't", said Chan.