Immunologist Sir John Bell spoke after France changed its advice about who should receive the AstraZeneca vaccine for the third time in a week. The EU nation suspended its use for several days last week after there were unfounded claims that it led to blood clots.
Before this French President Mr Macron suggested it was only suitable for those younger than 65.
And finally on Friday the Government reintroduced the jab but said it will only be administered to the over 55s.
Sir John, who is advising the UK Government on its own rollout, said the constant changes of policy in France were undermining confidence in the whole vaccination programme.
Speaking on the BBC Radio 4 Today programme, he said: “It doesn’t make any sense. The whole thing looks completely crackers.
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He added: “If there are clotting problems associated with the vaccines – I am not saying there are, but if there were – they are at a very tiny level compared with the problems you get if you get the disease. If you want to die of a clot, get Covid.”
The professor spoke after Mr Macron faced huge pressure over the rollout domestically.
He was made a mockery in the French press after contradicting his own Prime minister about the vaccine.
Jean Castex insisted his country “must have confidence in the Astra Zeneca vaccine” and later even had the jab personally.
But within 12 hours, Mr Macron performed a stunning U-turn and suspended its use before allowing it in the over 55s on Friday.
French newspapers lambasted the embattled president for his bungling pandemic response and blamed him squarely for the fiasco.
Speaking on France24, press reviewer Alison Sargent discussed how “French papers are really united” in criticising Mr Macron’s handling of Covid.
This follows France’s decision to impose a fresh lockdown on Paris and parts of northern France amid spiralling Covid cases.
The widespread condemnation comes just weeks after the president claimed, without evidence, that the AstraZeneca vaccine “doesn’t work the way we were expecting it to”.
Authorities later backtracked and French Health Minister Olivier Véran said: “Anybody aged 50 or over who is affected by comorbidities can get the AstraZeneca vaccine, including those between 65 and 74.”
The ongoing row couldn’t come for a worse time for Mr Macron – who goes to the polls next year hoping to secure a second term.
Current projections have him neck and neck with far-right National Rally leader Marine Le Pen – who he convincingly beat in 2017.
The UK, in contrast, could come out of lockdown two months earlier than France, the research company Airfinity estimates.
Imperial College London also estimated that lockdown costs up to £18billion a month – allowing the early release date to earn the UK up to an extra £36billion – when compared with France.