Geneva (dpa) - Around 60 to 70 per cent of population needs to be immunized against the novel coronavirus to curb infections, according to a senior World Health Organization (WHO) official.

The rate is based on several modelling studies, the head of WHO's vaccine department, Katherine O'Brian, told a press conference in Geneva on Friday.

O'Brien stressed, however, that the actual necessary immunization rate for this pandemic will only become clearer once more is known about the vaccines that have been tested so far.

"It's really important that we start to get more information," she said.

Besides knowing how well vaccines prevent the Covid-19 disease, the question is whether they make it harder for the virus to take hold in the nose and throat of people who do not have symptoms, and whether vaccines make it harder for the virus to pass from one person to another, O'Brian added.

In recent days, pharmaceutical companies AstraZeneca, Moderna and Pfizer/BioNTech have reported promising trial results for their three candidate vaccines.