The GAVI global vaccines alliance is seeking to raise $7.5 billion at a funding conference in Berlin next week, as its battle to prevent infectious diseases in millions of children reaches an expected peak.

The non-profit organization, launched in Davos 15 years ago, aims to immunize another 300 million children between 2016 and 2020, saving an estimated 5-6 million lives.

The economic benefits of that will be some $80 billion and $100 billion, underscoring the cost-effectiveness of vaccines as a centerpiece of public health, Chief Executive Seth Berkley told the World Economic Forum on Thursday.

Berkley said GAVI had already received extremely strong support from several governments but other major donors that have backed past funding rounds, notably the United States, have yet to show their hand ahead of the Jan. 26-27 Berlin talks.

One factor complicating the financing request is the strength of the dollar. GAVI buys its vaccines in the U.S. currency, while some donors will face higher costs in local currencies.

"We made our original requests almost seven months ago and exchange rates have dramatically changed. That is a challenge that we will have in front of us and will be discussed by the donors," Berkley said.

GAVI, which is backed by the Bill & Melinda Gates Foundation, the World Health Organization, the World Bank, UNICEF, donor governments and others, funds immunization programs for nations that cannot afford standard prices.

The group targets common but deadly diseases such as pneumonia, diarrhea and cervical cancer.

GAVI uses its bulk-buying power to negotiate big price discounts with drugmakers like GlaxoSmithKline and Pfizer, although some have argued it should strike even tougher deals with companies.

A full budget will also position GAVI to intervene in emergency situations such as Ebola, where it has already pledged to fund vaccine purchases once products are developed.

The coming 2016-20 period will be the busiest in GAVI's history, as it ramps up vaccine purchases to 2.7 billion doses from 2.1 billion in the preceding five years.

Beyond 2020, however, GAVI's immunization programs are set to tail off, as many countries with growing economies become too wealthy to be eligible for its help.

"This is peak GAVI," Berkley said. "We actually discussed whether we should consider going out of business and we looked at 2030 as a possible date, but the challenge is that there will still be about 20 eligible countries, assuming the modeling is correct, and the majority are pretty fragile states."