* Money would fund GAVI's programmes from 2016 to 2020
* GAVI works with drugmakers to cut vaccine costs for poor
* 1.5 mln children a year die of vaccine-preventable disease
By Kate Kelland
LONDON, May 20 (Reuters) - The GAVI global vaccines alliance issued a plea on Tuesday for $7.5 billion to help immunise another 300 million children against life-threatening diseases between 2016 and 2020 and save up to 6 million more lives.
GAVI said the additional investments, which it hopes to get mainly from global health philanthropists and the governments of developed nations, could double the total number of lives saved through GAVI-supported vaccines to an estimated 12 million.
"We are faced with an historic opportunity to support countries to build sustainable immunisation programmes that will protect entire generations of children," the group's chairman, Dagfinn Hoybraten, said in a statement.
"The investments we all make now can ensure the equivalent of two children every second will be reached with GAVI-supported vaccines for five years and secure the future health and economic prosperity of all our children in years to come."
GAVI, which is backed by the Bill & Melinda Gates Foundation, the World Health Organisation (WHO), the World Bank, UNICEF, donor governments and others, funds immunisation programs for poor nations that cannot afford to buy vaccines at rich-world prices.
The group targets common but deadly diseases such as pneumonia, diarrhoea and cervical cancer and says it has already saved around 6 million lives since its launch in 2000.
Seth Berkley, GAVI's chief executive, told Reuters that if the alliance were to achieve its target of an extra $7.5 billion, this would be added to $2 billion already in hand for the 2016 to 2020 period.
This is around 15 percent more than GAVI has for the current five-year period, he said, but an acceleration is necessary because there are still around 1.5 million children who die each year of vaccine-preventable diseases.
Berkley said the economic benefits of fully funded, sustainable vaccine programmes in poorer countries would result in between $80 and $100 billion in gains, partly by cutting the costs of treating illness, and increasing population productivity by keeping people alive and well into adulthood.
GAVI uses its private and government donors' backing to negotiate with pharmaceutical firms such as GlaxoSmithKline , Merck and Pfizer to bring down vaccine prices for the poor. It then works with partners to bulk-buy and deliver them to countries whose populations need them most.
The group says its influence on the vaccines market so far has led to a 37 percent decrease in the cost for a GAVI-eligible country to vaccinate a child with pentavalent, pneumococcal and rotavirus vaccines since 2010. (Editing by Alison Williams)