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THE global covid-19 vaccine roll-out is accelerating, with in excess of 300 million doses now administered. This time last year, such an achievement would have been almost a pipe dream.

Great challenges remain in ensuring the equitable distribution of vaccines across the world and persuading those who are hesitant that vaccination is in their best interests and in the interests of those around them. But even in countries where vaccines are available and take-up is high, emerging issues threaten the success of comprehensive vaccination programmes.

One concern is that the vaccination strategies of some countries might not be …