The head of the world's largest vaccine maker has said it is “unethical” to give third doses of the Covid-19 vaccine while developing nations are struggling to access first and second jabs.

“It's unethical to start giving three doses to somebody when others in certain countries and populations have not even got two doses,” Adar Poonawalla, billionaire chief executive of Serum Institute of India, told reporters.

He added it was “not right” to roll out booster shots when poorer countries have “not been able to get the vaccines purely because the rich nations have taken away most of the vaccines”.