Pfizer C-E-O Albert Bourla says people will "likely" need a third COVID-19 vaccine dose within 12 months of receiving the first two.
In an interview with C-N-B-C, Mr Bourla also flagged the possibility of annual re-vaccination, which are known as booster shots.
The news comes as Europe passed a grim milestone, tallying more than one million COVID-19 deaths since the start of the pandemic.
W-H-O Regional Director for Europe, Dr Hans Henri Kluge, describes Europe's COVID situation as very "serious".
Put simply, European countries are doing their own thing when it comes to vaccine roll outs.
Denmark has totally abandoned the use of the AstraZeneca vaccine, while other countries continue to use it for very specific age groups.
Johnson and Johnson vaccine administrations have been paused in most countries, while others go ahead with it as investigators examine blood clotting concerns.
Norway is taking extended time to assess whether to resume the use of the AstraZeneca vaccine or stop it altogether.
A new Oxford study supports the blood clotting conclusions made by World Health Organisation officials.
New data suggests the risk of developing a serious brain clot - known as a cerebral sinus vein thrombosis - is 8 to 10 times higher in people with COVID-19 than in those vaccinated against it.
Findings show that while these blood clots are uncommon after contracting coronavirus, with 39 in every million people developing one within two weeks of being ill - they are much rarer still after a vaccine.
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