The two scientific committees under the Centre for Health Protection today recommended that adults should get a third COVID-19 jab after they received two doses, and those aged 12 to 17 can get two shots of the BioNTech vaccine with at least a 12-week interval.

The committees convened a joint meeting today and met the media afterwards.

Scientific Committee on Emerging & Zoonotic Diseases Chairman Prof David Hui said experts strongly recommended that people aged 18 or above who had received two vaccine doses, regardless of whether they were the Sinovac or BioNTech vaccine, should get a third jab at least six months after the second one.

But those who have personal needs can get the additional dose earlier, he noted.

"Currently there is no community outbreak of the Omicron variant. Also, if you provide the public with a third dose of a COVID-19 vaccine, with time the antibody levels will drop anyway.

"So after balancing the risks and the benefits, the optimal timing for the purpose of maintaining intervals between the second and third dose in Hong Kong is six months for the majority of people.

"But as I said before, if you are in need of going overseas to study or for business reasons, then you can actually have the third dose earlier - between three to six months after the second dose."

The committees previously recommended that teenagers aged 12 to 17 should only receive one dose of the BioNTech vaccine instead of two, as some myocarditis cases were reported among those who had received the second jab.

As of mid-December, around 70,000 teenagers of this age range have completed their first jab.

Citing the latest data, Scientific Committee on Vaccine Preventable Diseases Chairman Prof Lau Yu-lung said two doses of the BioNTech vaccine with a longer interval would result in a better immune response for young people and the risk of myocarditis is also lowered.

"We have got two or three more months of data. We analysed the data and reached the conclusion that these 70,000 adolescents (aged 12 to 17) could consider - of course they need to have their parents' consent - receiving the second dose with an interval of not less than 12 weeks.

"And of course that must be informed consent stating that the second dose with a 12-week interval would result in the myocarditis rate reduced by at least one-tenth."

Prof Lau added that those teenagers can choose to have the injection of the BioNTech vaccine in the mid-anterolateral thigh in order to reduce the risk of having myocarditis.