A promise to reduce the prices of vaccines in developing countries has been announced by a number of big drug companies, ahead of a conference in London at which political leaders will consider how to raise funds for immunisation.

The Global Alliance for Vaccines and Immunisation (Gavi), set up by Microsoft founder Bill Gates, said yesterday that Serum Institute of India and Panacea Biotec had agreed to reduce the prices of their pentavalent vaccine, which protects against five fatal diseases. And GlaxoSmithKline has agreed to sell a vaccine against diarrhoeal disease in the poorest countries for £1.50 a dose, a twentieth of its £30 price in developed countries.

"I hope this will enable millions of children to receive this vaccine," alliance chief executive, Andrew Witty, wrote in the Times. "Importantly, this offer is sustainable, because we are recouping the cost of goods and manufacture." Calling on drug companies to be "in step with society", Witty said they should construct their goals around business models that address the world's urgent health needs.

Merck & Co has also pledged to offer its rotavirus vaccine at discounted prices, said the alliance. The various offers are in response to a tender by United Nations Children's Fund, which takes most of the vaccines funded by the alliance.

Gavi donors meet in London on 13 June, where David Cameron will promote a plan to raise a further £2.25bn in global aid.