Malaysia's health ministry has granted conditional approval for the Covid-19 vaccine made by Pfizer and BioNTech to be used as a booster shot, Reuters reports.

The approval allows the vaccine to be used only on adults aged 18 and above, at least six months after they have received their second dose, the ministry said in a statement.

Authorities earlier said booster shots would not be compulsory but were highly recommended for those in vulnerable and high-risk groups.