A top official in the European Medicines Agency said it might be worth abandoning AstraZeneca's coronavirus vaccine for all age groups where alternatives were available.
Marco Cavaleri, the EMA's head of vaccine strategy, also told Italy's La Stampa newspaper that Johnson & Johnson's vaccine should be preferred for those aged over 60.
The so-called viral vector vaccines are authorised for everyone over 18 but have been put in doubt by reports of rare blood clots.
The EU has also authorised the messenger RNA vaccines from Pfizer-BioNTech and Moderna.
Italy on Saturday restricted AstraZeneca vaccines to people aged 60 and over after concerns about the health risks for younger people.
Mr Cavaleri said it would be better to ban AstraZeneca, including for the over 60s.
"Yes, and it is an option that many countries, such as France and Germany, are considering in the light of the increased availability of mRNA vaccines," he said.
"However, incidents were very rare and after the first dose. It is true that there is less data on the second dose, but in the United Kingdom, it is going well.
"Among young people, the risks of illness decrease, and the message for them could be to use preferentially the mRNA vaccines but the choice is left to individual states."
Mr Cavaleri said the single-shot Johnson & Johnson vaccine has "fewer problems than AstraZeneca", but it had been less widely used.
"With one dose it is useful for some categories that are difficult to reach, but it remains an adenovirus [vaccine] and it is preferable to reserve it for the over-60s," he said.
The EMA later tweeted: "Misinformation is making the rounds today.
"This is the situation: the benefit-risk balance of AstraZeneca Covid-19 vaccine is positive and it remains authorised for all populations."
Messenger RNA technology trains the body to reproduce spike proteins, similar to that found on the coronavirus.
When exposed to the real virus later, the body recognises the spike proteins and is able to fight them off.
Viral vector vaccines such as those from AstraZeneca and Johnson & Johnson use a genetically engineered version of a common cold-causing adenovirus as a "vector" to shuttle genetic instructions into human cells.
