Thailand has detected the South African variant of the coronavirus among a cluster of infected undocumented migrants in Narathiwat province.
Independent scientists and members of the Covid-19 Network Investigations group on Saturday reported to the Public Health Ministry that they found the B.1.351 variant, commonly known as the South African strain, from samples the ministry collected from the cluster in Tak Bai district on May 13.
The group said the strain contains spike mutations that may affect the reaction of the immune system and reduce the efficacy of most vaccines.
However, it said this does not mean that vaccines are ineffective in preventing infections, though Thailand may need to vaccinate more of the population to achieve herd immunity.
"The variant may impact human immunity response from the virus and reduce the effectiveness of the vaccine," said the alliance, which conducts genomics surveillance and research and has worked closely with the government during the pandemic.
"This does not mean that the vaccines do not work but there must be an increase in the ratio of population receiving the vaccine," the report said.
Thailand detected the South African variant on Feb 15 in a man who had travelled from Tanzania and was put under the mandatory quarantine upon arrival.
But the discovery of a domestic transmission of the variant could complicate the country's efforts to tackle its worst Covid-19 outbreak so far.
Dr Thiravat Hemachudha, head of the Center for Emerging Disease Health Sciences at the Faculty of Medicine at Chulalongkorn University, said finding the South African strain outside of quarantine centres implies that the strain is spreading in Thailand.
He urged the government to speed up its vaccination campaign.