Experts who advise the government on Covid-19 jabs recommended on Friday that the gap between a first and second dose of the BioNTech vaccine be extended to lower the risk of myocarditis, or heart inflammation.
They said the dosing interval should be increased from three to eight weeks for people aged between 18 and 59.
Around 88 percent of Hongkongers over the age of 3 have already received two doses of Covid vaccine.
The updated "interim recommendation" comes after the experts from the joint-scientific committees under the Centre for Health Protection and the chief executive's expert advisory panel discussed the matter.
"There is more evidence suggesting a longer dosing interval between the first and second doses of Comiranty vaccine would result in better immune response and lower risk of myocarditis," said the joint-scientific committees.
But they added that people can still get the second jab after three weeks if they have personal needs, and after considering individual risk and benefit.
Separately, the experts are not recommending mass vaccination against monkeypox, but say those who have been exposed to infected people, as well as high-risk groups such as medical workers caring for confirmed patients, would be recommended to get jabs if they are available.
A number of countries around the world have recently reported cases of monkeypox, which is normally found in Africa, but Hong Kong hasn't recorded any infections.