LONDON, (Reuters) - - More children worldwide are now immunized against killer diseases but the task has become harder due to conflicts, epidemics, urbanization and migration, the head of a global vaccine group said.

FILE PHOTO: A Rohingya refugee boy who crossed the border from Myanmar a day before, gets an oral cholera vaccine, distributed by UNICEF workers as he waits to receive permission from the Bangladeshi army to continue his way to the refugee camps, in Palang Khali, near Cox's Bazar, Bangladesh October 17, 2017. REUTERS/ Zohra Bensemra/File Photo

Seth Berkley, chief executive of the GAVI vaccines alliance, said his agency was now focusing on how to get vaccines to people in rural areas, those isolated by war and refugees.

GAVI uses its funding by private philanthropies and government donors to negotiate down vaccine prices for poorer nations, buying them in bulk to supply countries most in need.

Since its launch in 2000, the alliance has helped save the lives of about 10 million children and immunized 700 million children with new and generic vaccines against everything from measles to diarrhea to cervical cancer.

“Ninety percent of children in the world are now reached by routine immunizations, but there are 10 percent that aren’t,” Berkley told Reuters by telephone from a GAVI meeting in the United Arab Emirates.

“And there are more and more (disease) outbreaks around the world - partly because of climate change, partly because of instability - and we have the largest number of refugees in history,” he said.

He cited U.N. data showing there were now almost 70 million displaced people worldwide.

“So to deal with those challenges, GAVI has to adapt its model to work more flexibly,” Berkley said.

The alliance has traditionally worked with governments to raise routine vaccine coverage rates in poor countries.

More recently it has also worked on emergency projects, including getting oral cholera shots to Rohingya refugees in Bangladesh, stockpiling an experimental Ebola vaccine for use in an epidemic in Democratic Republic of Congo, and trying to help prevent infectious disease flare-ups in Syria.

Berkley said GAVI was also now finding new partners.

In Uganda, it is working with the delivery firms UPS and Freight in Time Ltd, and with Parsyl, a data start-up, to use customized apps, data and wireless temperature monitoring to overcome vaccine supply chain issues.

GAVI is also working with the German development bank KfW to explore using blockchain technology in its cash support and supply chain management.

Payments firm Mastercard has said it would offer advice and technology to help provide digital immunization record cards in poorer countries.

“It’s about understanding where people are being missed,” Berkley said, adding that this was increasingly in “urban slums, isolated rural areas and conflict areas in fragile countries”.