It is unclear to what extent COVID-19 vaccines can interrupt transmission of the coronavirus, a World Health Organization (WHO) expert said at the daily media briefing on Friday.

"We actually don't have the information right now about that the magnitude, the degree to which they interrupt transmission," said Kate O'Brien, director of WHO's Department of Immunization, Vaccines and Biologicals.

"Although we do have evidence now about the degree to which they can protect against disease, especially severe disease, that does not necessarily imply the same magnitude of impact will be on the protection against transmitting from one person to the next person." 

The world is now rushing to implement vaccination, and "there will be an ever-increasing number" of people who receive the COVID-19 vaccine jabs. However, even those who have been vaccinated cannot be fully protected from getting infected, said O'Brien.

She added that a new study shows that 59 percent of transmissions come from asymptomatic people.

O'Brien's remarks echoed Maria Van Kerkhove, technical lead of WHO Health Emergencies Programme, who said a vaccine is just a new and very powerful tool. She called on the public to support government guidelines and contribute to decreasing transmission.

"The decisions that you make every single day about what you want to do versus what you need to do matter," said Van Kerkhove.