The new study has confirmed that the Pfizer vaccine offers great protection against the virus in the first weeks since being administered.
But the findings also suggest the protection will gradually wane with time for some people.
Countries like the US, UK and Israel are already offering booster shots to certain people in a bid to bolster their immune systems.
In the US, infectious disease official Dr Anthony Fauci has called on the “overwhelming majority” of vaccinated Americans to sign up for a booster shot.
In the UK, booster shots are being offered on the NHS to people aged 40 and over, as well as frontline workers, and people who live and work in care homes.