Gordon Brown and the Pope are trying to save millions of children in the poorest countries by speeding distribution of life-saving vaccines.
A group of world leaders, including the Chancellor and Pope Benedict XVI, launched the £750m scheme in Rome yesterday.
The audience with the Pope could also bring domestic political benefits for Mr Brown, so soon after the conflict between the Government and the Catholic Church over whether gay couples should have in adoption law similar rights to heterosexuals. The row threatened to erode Labour's traditionally strong base among working-class Catholics, with vital local elections looming in Scotland in May.
Also at the ceremony in Rome were Queen Rania Al-Abdullah of Jordan and Paul Wolfowitz of the World Bank launching the "Advance Market Mechanism". Italy, the UK, Canada, Norway, Russia and the Gates Foundation are to create a £750m fund that will give the poorest countries purchasing power in the drugs market, spurring pharmaceutical companies to develop the needed drugs. Mr Brown told The Independent: "It will give them the power to buy at discounted prices a suitable vaccine when one becomes available. At a stroke, it turns a vague hope for a medical breakthrough into an immediate reality. It will now make economic sense for pharmaceutical companies to develop the new vaccine."
He added: "Of course, drugs and vaccines are only part of the answer of addressing the arithmetic of disease and death. Weak health systems and insufficient doctors and nurses are among the main obstacles to access to basic health care. Nothing less than a bold commitment to action is now needed."
The first disease to be targeted will be pneumococcal infection, the main cause of deaths from pneumonia among children, and the second leading cause of childhood meningitis deaths. It kills more than 1.6 million people, including nearly a million children under five, every year.
Worldwide, nearly 10 million children under five die every year, or about one every three seconds. A quarter of these deaths are caused by diseases such as measles, polio, diphtheria and hepatitis, for which there are vaccines available. There are no effective vaccines yet for malaria, pneumonia, tuberculosis and Aids, which kill seven million under-fives a year.
The fund founders hope that by stimulating the market in life-saving drugs, five million lives will be saved by 2030.
Private-sector pharmaceutical research is heavily tilted towards tackling health problems found in the richer countries, where companies are guaranteed a lucrative market for any effective treatment. Every year, more than £50bn is spent globally on health research, but only 10 per cent goes on the diseases that cause 90 per cent of all health problems.
While Mr Brown was in Rome he also had talks with the Italian Prime Minister, Romano Prodi.