The writer is co-director of the Institute of Global Health Innovation at Imperial College London and chair of Pre-emptive Medicine and Health Security Initiative at Flagship Pioneering, the bioplatforms company that founded vaccines maker Moderna

As countries in the global north scale up their Covid-19 vaccination programmes, the world’s poorest countries are being left behind. While most of the world’s population is yet to receive a single dose, some countries are already planning booster shots for later in the year.

A new strategy could release hundreds of millions of doses from advanced economies to less developed countries. Rather than offer booster doses to the whole population, countries could establish Covid-19 protection screening programmes. Antibody levels would be tested and quantified, and booster shots would only be offered to those who needed it.