Boris Johnson has urged world leaders to join together and focus their “collective ingenuity” on the search for a coronavirus vaccine that is affordable and available to all.

The Prime Minister made the call as he opened the Gavi vaccine alliance summit seeking to raise £6 billion to immunise 300 million children against infectious diseases within five years.

Mr Johnson said the UK would remain the world’s leading donor to the partnership, contributing £1.65 billion over the next five years.

And he urged foreign leaders to “join us to fortify this lifesaving alliance, and inaugurate a new era of global health co-operation which I believe is now the most essential shared endeavour of our lifetimes”.

Representatives from 50 countries are expected to join the virtual summit, hosted by the UK, which comes against the backdrop of the coronavirus pandemic.

If the funding target is met, it is hoped 300 million children in the world’s poorest nations could be vaccinated against diseases like polio, diphtheria and measles by 2025.

Mr Johnson said: “To defeat coronavirus we must focus our collective ingenuity on the search for a vaccine and ensure that countries, pharmaceutical companies and international partners, like the World Health Organisation, co-operate on a scale beyond anything we have seen before.

“We must use the collective purchasing power of Gavi, the vaccine alliance, to make that future vaccine affordable and available to all who need it.

“If we are to make this the beginning of a new era of global health collaboration, we must also replenish the funding for the vaccines we already have, strengthening the routine immunisation against preventable diseases in the poorest countries.”

Mr Johnson will deliver a keynote speech later on Thursday.

Microsoft founder Bill Gates will also address the summit and at least 35 heads of state or government are expected to attend.