The new Omicron subvariant CH.1.1, which has been detected in 67 countries including Thailand, can evade immunity produced by long-acting antibody (LAAB) vaccines but its rate of transmission is low, according to the Department of Medical Sciences says.
Dr Supakit Sirilak, the department chief, said there is concern that CH.1.1 might might prove detrimental to the efficiency of the LAAB shots that are used for those who have a compromised immune system, such as those with chronic kidney disease, cancer and organ transplant patients.
The department has only diagnosed around 300 patients so far, he said, adding that the majority of cases at the moment, about 80%, are caused by the BN.1 subvariant of the novel coronavirus.
He insisted that LAAB shots are still effective as a treatment to enhance human immunity against Covid-19.
“We closely monitor virus mutations, of which BN.1 has been the dominant subvariant since January. We don’t think that CH.1.1 will replace BN.1 due to their different transmission rates,” he said on Tuesday.
People travelling to China, India, Nepal and Myanmar must take an RT-PCR test before arrival. Based on 2,022 cases recorded between Jan 8 and Feb 3, the department found a decline in positive test results from 10% to 1% among Thai people, with a corresponding drop among Chinese tourists from 7% to 2%.
In the week from Jan 28 to Feb 3, 94 people — 87 Thais and seven foreigners — tested positive for Covid-19 during initial examinations.
The BA.2.75 subvariant was detected in 82 cases, followed by BA.4/BA.5 in 8 cases and others in the remaining four cases, said Dr Supakit.
Dr Supakit also said the department would reduce complications in monitoring for virus mutations by using whole genome sequencing every two weeks, instead of conducting the single nucleotide polymorphism (SNP) genetic test for specified subvariants.
In a related development, a source from the Department of Disease Control said that the cabinet had agreed to receive 1.5 million doses of second-generation vaccines donated by South Korea and France, which are expected to arrive shortly.
It will be the first time that Thailand will use the second generation of bivalent vaccine, which was developed by combining molecules of the spike proteins from the original virus and the Omicron variant.
“We have enough vaccine and no plan to buy the second-generation. But if they intend to donate the latest version, we are willing to accept it,” said the source.
The department will set up a committee to clarify which groups should be prioritised to receive the newer jab.