Delaying the second dose of the mRNA coronavirus vaccines in younger people may lead to fewer deaths, but only if certain conditions are met, a predictive modelling study suggests.

The findings add to the current pandemic debate over whether to extend the gap between vaccine doses to give as many people as possible some protection, or to stick with the dosing intervals designated in clinical trials.

For example, Pfizer has said there is no clinical evidence to support the UK’s decision to extend the gap between doses of its vaccine from 3-4 weeks to 12 weeks.

But data from the rollout in England shows protection against death of around 80% from one dose, with a 70% decline in infections.