The Department of Medical Sciences has found that a combined formula between a full inactivated vaccine and an mRNA-based vaccine as a booster produces a high level of immunity against both the Delta and Omicron coronavirus variants.
Department chief Dr Supakit Sirilak said data from a test involving 80 people showed that all Covid-19 vaccines produced low levels of immunity against Omicron when compared to Delta.
But immunity levels significantly increased after getting a mixed boosting dose, especially from an mRNA-based vaccine, Dr Supakit said during a press conference.
"The study shows we do need to get a booster vaccine for fighting against the Omicron variant," he said.
"I would like to recommend all people, especially those considered at high risk from the disease, to get the booster vaccine as soon as possible."
The study looked at immunity levels against both variants two weeks after test participants got a booster shot.
The test was done under the Plaque Reduction Neutralisation Test (PRNT) method.
Test results showed a very high level of immunity against the two variants.
According to the study, the level of immunity increased to 282.5 and 729.3 for Omicron and Delta respectively from a full dose of Sinovac mixed with a smaller amount of Pfizer.
A similar effective result was seen with 222.9 and 691.1 from a mixed dose of AstraZeneca and Pfizer given at a similar ratio.
All two-dose vaccines showed a low level of immunity against the Omicron strain. For example, two-doses of AstraZeneca reached only 23.81 against Omicron, 19.17 for Pfizer and 11.63 for a combined Sinovac and AstraZeneca.
Dr Supaporn Phumiamorn, director of the Institute of Biological Products who conducted the study, said laboratory tests found Omicron would reproduce its number of cells quite slowly compared with Delta, which led to fewer health impacts of those infected with the new variant.
The Department of Medical Sciences is next going to study the length of valid immunity after vaccination, which will take some time to get results.
