The EU medicines watchdog on Wednesday approved a second Covid booster jab for people aged 80 and over, but said it was too early to make a finding on other age groups.
The announcement by the European Medicines Agency and the European Centre for Disease Prevention and Control comes as many countries drop coronavirus measures despite a continued spike in infections.
"A fourth dose (or second booster) can be given to adults 80 years of age and above after reviewing data on the higher risk of severe Covid-19 in this age group and the protection provided by a fourth dose," a combined EMA and ECDC statement said.
However a combined EMA-ECDC task force have concluded that it is too early to consider using a fourth vaccine dose to he general population, they said.
There is currently no clear evidence that immunity is waning in people aged 60 to 79 with normal immune systems "and thus no clear evidence to support the immediate use of a fourth dose".
"If the current epidemiological situation changes and new signals emerge, it may become necessary to consider a fourth dose in this age group," the agencies said.
"For adults below 60 years of age with normal immune systems, there is currently no conclusive evidence that vaccine protection against severe disease is waning or that there is an added value of a fourth dose," they said.
More than two years into the pandemic, which has officially caused more than six million deaths -- with the true figure believed to be several times as high -- the resurgence in cases can mainly be blamed on the spread of infectious sub-lineages of the Omicron variant, particularly BA.2, the EMA said last month.
The regulator has so far approved five vaccines for use in the EU: Pfizer, Moderna, AstraZeneca, Johnson & Johnson and Novavax.