People who have received a Covid-19 vaccine could still pass the virus on to others and should continue following lockdown rules, England’s deputy chief medical officer has warned.
Writing in the Sunday Telegraph, Prof Jonathan Van-Tam stressed that scientists “do not yet know the impact of the vaccine on transmission”.
He said vaccines offer “hope” but infection rates must come down quickly.
Matt Hancock said 75% of over-80s in the UK have now had a first virus jab.
Both the Pfizer-BioNTech and Oxford-AstraZeneca vaccines require two doses, and figures so far reflect those given the first dose.
The health secretary told the BBC’s Andrew Marr that around three quarters of care homes had also been vaccinated.
Prof Van-Tam said “no vaccine has ever been” 100% effective, so there is no guaranteed protection.
It is possible to contract the virus in the two- to three-week period after receiving a jab, he said – and it is “better” to allow “at least three weeks” for an immune response to fully develop in older people.
“Even after you have had both doses of the vaccine you may still give Covid-19 to someone else and the chains of transmission will then continue,” Prof Van-Tam said.
“If you change your behaviour you could still be spreading the virus, keeping the number of cases high and putting others at risk who also need their vaccine but are further down the queue.”
Last week, the person coordinating Israel’s Covid response reportedly suggested a single dose of the Pfizer vaccine might not be as effective as reported.