There is no clear evidence in the European Union that vaccine protection against severe disease is waning substantially in adults with normal immune systems aged 60-79, the European Medicines Agency (EMA) and the European Centre for Disease Prevention and Control (ECDC) said in a joint statement.
They cautioned, however, that it may become necessary to consider a fourth dose in this age group if the epidemiological situation changes.
Both agencies agreed a fourth dose can be given to adults 80 years of age and above.
That recommendation came a week after European health ministers urged the bloc's executive to back a fourth COVID-19 shot for people over 60 to boost immunity in the absence of vaccines that specifically protect against the omicron variant.
A study from Israel has shown that senior citizens who received a second booster of the Pfizer–BioNTech COVID-19 vaccination had a 78% lower mortality rate from the disease than those who had only one.
The agencies said there was no conclusive evidence of "an added value of a fourth dose" in those aged below 60.
The agencies will consider the best timing for additional doses, possibly taking advantage of updated vaccines when re-vaccination campaigns start in the autumn.