The Public Health Ministry is speeding up a study looking into the need for a third Covid-19 vaccine shot for people who are fully vaccinated as certain coronavirus variants are more infectious than others.
Along with this study, a ministry committee is tasked with assessing whether it is safe for people to be jabbed using different vaccine brands after the initial first shot is given, said Dr Opas Karnkawinpong, director-general of the Department of Disease Control (DDC) on Monday.
Dr Opas, however, insisted it was still too soon to say whether a booster shot is actually needed and if the shot can come from a different manufacturer.
"Knowledge [about the virus and the vaccines is updated] constantly so we need to wait until we have sufficient information to support any new decisions to make," he said. "We have a team that is following up on this and will decide what will be the most suitable [for Thailand's situation]."
Dr Opas was responding to questions over the need for a booster shot for vaccine recipients in Thailand and whether it could come from a different brand.
He said the ministry's study is similar to one being conducted by a team led by Dr Yong Poovorawan, head of the Centre of Excellence in Clinical Virology at Chulalongkorn University.
The number of people in Thailand infected with the Delta coronavirus variant, which first emerged in India, is increasing and likely to replace the Alpha variant, first identified in Britain, as the dominant strain causing infections, Dr Yong said.
Citing findings from a new study published by the British medical journal The Lancet on June 14, he said a considerably higher level of immune response to a Covid-19 vaccine is needed as an efficient defence against the Delta variant.
Both the Pfizer and AstraZeneca vaccines were cited in this study, he said, adding a study carried out in Scotland showed they were less effective in preventing infections caused by the Delta variant.
Fourteen days after a second shot, the Pfizer vaccine was found to be 79% effective in preventing Delta variant infections, while the AstraZeneca vaccine was 60% effective against the strain, Dr Yong said.
In a similar situation, those vaccines were found to be up to 92% and 73% effective against the Alpha variant, he said.
"While most cases here are now found to be of the Alpha variant, the Delta variant will in the next few months dominate in Thailand, given the [mutation] of this particular virus variant," Dr Yong said.
Thailand may have to shorten the period between first and second AstraZeneca shots to mitigate the severity expected to be caused by the Delta variant, he said.
As for other Covid-19 vaccines that induce lower rates of immune responses, he said, third shots may need to be used as boosters while the kingdom waits for new vaccines to be developed to specifically deal with the Delta variant.
"In the meantime, Thailand needs to closely monitor how each existing coronavirus variant is spreading to keep track of them all, especially the fast-spreading Delta variant," Dr Yong said.
In response to growing public concern over lower immune responses induced by Covid-19 vaccines, Dr Opas said the ministry is also monitoring information taken from the ongoing mass vaccination drive.
The government is in talks with vaccine suppliers but some of these companies do not want to disclose too much information about vaccine deals, he said.
However, everyone in the country will be vaccinated as promised, Dr Yong said.
Japan has agreed to donate AstraZeneca Covid-19 vaccine doses to Thailand, which are expected to arrive next month, said Deputy Prime Minister and Public Health Minister Anutin Charnvirakul.
The exact amount remains unconfirmed, he said.
When asked how confident he was in the government's plan to reopen the country in 120 days, Mr Anutin said the decision is up to the Centre for Covid-19 Situation Administration (CCSA) and the ministry will work to support the CCSA.
He said Thailand has so far secured 8.5 million more doses from AstraZeneca and Sinovac this month alone, up from the initial target of 6 million.
