It is safe to administer COVID-19 vaccine booster shots as early as three months from completion, according to the European Union's drugs regulator.

People that have completed their two-shot regimen are currently advised to wait six months before taking their booster shots.

"While the current recommendation is to administer boosters preferably after six months, the data currently available support safe and effective administration of a booster as early as three months from completion," Reuters quotes the European Medicines Agency's (EMA) Head of Vaccines Strategy, Marco Cavaleri, to say.

Cavaleri's remarks come as the world is on high alert following the emergence of the new Omicron variant, which has already spread to nearly 60 countries globally.

He noted that preparations are in full swing for the review of any redesigned vaccines that target the new Omicron variant, should it be needed, but the spread of the dominant Delta variant should for now be front and centre of the fight against the current wave.

"The immunological situation remains extremely worrying in Europe," said Cavaleri. "(Delta) will remain the main focus of public health actions to cope with the pandemic and its consequences,” Reuters quotes him.