Mr Johnson’s comment came as the UK remained locked in a stand-off with the EU over Brussels demands for “reciprocity” in imports and exports of doses.
EU leaders will decide in a virtual meeting on Thursday whether to block the delivery of supplies which the UK insists are due to be sent to Britain under contracts signed last year.
Speaking to the House of Commons Liaison Committee, Mr Johnson said that “arbitrary” blockades of vaccines were not “sensible” and warned that any country imposing them would make itself less attractive as a destination for investment by pharmaceutical firms.
“I don’t think that blockades of either vaccines or of the ingredients for vaccines are sensible,” said the prime minister.
“I think that the long-term damage done by blockades can be can be very considerable.”
And he added: “I would just gently point out to anybody considering a blockade or interruption of supply chains that companies may look at such actions and and draw conclusions about whether or not it is sensible to make future investments in countries where arbitrary blockades are imposed.”
EU leaders are furious that as many as 10m vaccine doses produced in continental Europe have been sent by AstraZeneca to the UK, while none have been exported from Britain to Europe.
The row comes at a time when EU vaccination programmes are lagging well behind the UK, with a new third wave of infections surging on the continent.
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