We must change how we use our precious Covid-19 vaccines

First dose potency and longer gaps before second can help get speedier herd immunity

“Individuals may have to wait up to twice as long for any vaccine if we continue to prioritise early second doses. Herd immunity effects will also likely be delayed.” File photograph: Emilio Naranjo/EPA

“Individuals may have to wait up to twice as long for any vaccine if we continue to prioritise early second doses. Herd immunity effects will also likely be delayed.” File photograph: Emilio Naranjo/EPA

The Government experienced a very mixed reception to the recent change in the Covid-19 vaccination programme. The decision had a compelling rationale, to prioritise those with greatest risk of severe Covid-19. There is a now a strong case for additional changes to accelerate and maximise benefit.

A single dose of any available vaccine offers very substantial probability of protection, in the range of 60-85 per cent depending mainly on which vaccine is used. A second dose adds only 0-15 per cent to this. The cost of that second dose, offering at most 15 per cent additional protection to person A, means that unvaccinated person B is deprived of at least a 60 per cent chance of protection for some time.

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