Thai people are at risk of COVID Omicron variant infection, depending on several factors, said Dr. Thiravat Hemachudha, chief of the Thai Red Cross Emerging Infectious Diseases Health Science Centre today (Tuesday).

One factor, he said, is the drop in efficacy of the vaccines three months after inoculation, although the vaccines are regarded as the best currently available.

A three-dose course of the Pfizer or Moderna mRNA vaccines is said to be 10 times more effective than a three-dose course of AstraZeneca, but three months after inoculation, he said that the efficiency of Pfizer or Moderna vaccine will drop by about 40%, citing a study by Pfizer.

Unvaccinated people are vulnerable to infection, even if they have been infected with COVID-19 before and have recovered, said Dr. Thiravat.

For those who were inoculated or infected with COVID-19, if they are infected by the Omicron variant, their symptoms could be mild or serious, depending upon their immunological memory, which is the ability of the immune system to quickly and specifically recognise an antigen which the body has encountered previously and initiate an appropriate immune response, said the doctor.

Because the effectiveness of a vaccine will reduce after a certain period, Dr. Thiravat said the best way to administer a booster shot is via subcutaneous (under the skin) injection.

Medication to treat symptoms from the Omicron variant infection is as important as vaccination in reducing the risk of hospitalisation or death, he said, adding that such medications include the Fah Talai Jone Thai herbal medicine, Ivermectin, Fluoxetine or Fluvoxamine.

He made clear that administering booster doses is meant to slow the onset of the Omicron variant and does not prevent someone from getting infected by the virus.