While a booster is useful, a fourth shot of Covid-19 vaccine against the dominant Omicron variant is not yet necessary for most people, according to Dr Prasit Watanapa, dean of the Faculty of Medicine at Siriraj Hospital.
He said those who have received three shots should not rush to get a fourth as there is not enough evidence showing people need to get another dose every three to six months.
A recent study by Imperial College London suggested the general public should get a booster shot three months after receiving their second jab, and that a booster of either AstraZeneca or Pfizer can enhance efficiency against Omicron by 55%-80%.
In contrast, it found that people who only receive two doses of any vaccine may have no immunity against Omicron -- or just 20% at best.
"There is clear evidence showing that booster shots are necessary for fighting against Omicron," Dr Prasit said. "But none of the studies make a compelling case for a fourth dose. We should wait for more evidence ... especially when the second generation of vaccines is going to be launched soon."
However, he said the situation may be different for high-risk groups such as frontline medical personnel who may find a fourth shot more worthwhile.
The Omicron variant is known to be much more transmissible than other variants but usually results in less severe symptoms such as a runny nose, muscle aches, sneezing, and sore throat. Cases of high fever and loss of smell are much less common, Dr Prasit said, adding medicines such as favipiravir, molnupiravir and nirmatrelvir are all considered effective against this variant.
The doctor urged people who have been jabbed twice to get a third shot as soon as possible.
"Getting the vaccine is the best option to create herd immunity," he said, adding this is the best way of transitioning the pandemic into a more manageable epidemic.
