"You don't really know how long protection lasts until you've been able to study vaccinated people over time."
David Nabarro, the Director-General of the World Health Organisation (WHO), has urged people to be cautious following yesterday's positive news about a vaccine for Covid-19.
Nabarro was speaking on
Morning Ireland about the announcement from Pfizer that a clinical trials on a vaccine the company had been working on with BioNTech had revealed that it was more than 90% effective.
While agreeing that it is positive news, Nabarro urged people not to get complacent and to continue to follow safety guidelines.
He said: "We are being given advance warning of something brilliant but at the same time we have to be prepared for several weeks, perhaps even months more work before the vaccine or a vaccine like it can become available for people.
"You don't really know how long protection lasts until you've been able to study vaccinated people over time... it's a bit early to say whether this vaccine gives protection for weeks and months or even years."
The news that the vaccine is over 90% effective is hugely significant as regulators have previously discussed a willingness to approve a vaccine that is 50% effective, thereby protecting only half of those who would get it.
Pfizer and BioNTech say they expect to supply up to 50 million vaccine doses globally in 2020, and up to 1.3 billion doses in 2021.
