Correction: An earlier version of this editorial stated that Gavi requested $1 billion from the U.S. government from 2016 to 2020. The request was for the period from 2015 to 2018, while the broader global replenishment effort is from 2016 to 2020. The following editorial has been updated.

A girl cries as she receives a Polio vaccine shot in Sanaa June 11, 2012. Yemen began a three-day nationwide house-to-house immunization campaign on Monday. (Khaled Abdullah/REUTERS)

AN IMPORTANT conference is to be held in Berlin on Jan. 27 to secure financial replenishment for Gavi, the Vaccine Alliance, a multilateral nonprofit that for 15 years has been bringing vaccines to children in the world’s 73 poorest nations. Many attendees will be watching to see what the United States pledges to the effort for the next few years. It ought to be generous.

Vaccines, which prevent disease, are one of the most cost-effective ways to improve global public health. Gavi, originally known as the Global Alliance for Vaccines and Immunisation, had its origins in worries about declining global immunization rates. Since its founding in 2000 at the behest of Bill Gates, the alliance has helped immunize 440 million children and estimates it has saved more than 6 million lives. The Bill and Melinda Gates Foundation is a major donor.

In the coming five years, Gavi has set itself an ambitious goal of another 300 million children immunized, lifting the share of children who receive all 11 vaccines recommended by the World Health Organization from 5 percent to 50 percent in these poor countries. The group is seeking to raise $7.5 billion, and it has asked the United States to make a multiyear commitment, $1 billion from 2015 to 2018, compared with the $1.4 billion U.S. contribution over the past decade and a half.

A good reason for this is that the alliance negotiates with pharmaceutical firms to get lower prices for vaccines, which can take years to develop and are expensive. A multiyear timeline for donor support will boost Gavi’s bargaining position in this vital undertaking. Gavi now pays between $9.90 and $10.50 for a course of pneumococcal vaccine for children in these poor countries; in the United States, the equivalent vaccine coverage costs $456.

These are trying days in global public health. The World Health Organization hardly distinguished itself in responding to the Ebola virus outbreak in West Africa that has taken thousands of lives. Gavi, a relatively new organization attempting to demonstrate innovation in its methods, is now being asked to take on additional burdens. For example, the alliance has agreed to purchase millions of doses of an Ebola vaccine, once it’s approved for safety and efficacy, creating a market for manufacturers to ramp up production and perhaps save lives. The alliance also is getting more involved in the troubled polio eradication effort. These new directions are understandable and welcome but must not become a distraction from Gavi’s core mission.

Gavi devotes considerable resources to building health-care infrastructure in poor countries — investment that generates benefits even after an immunization campaign is over. Gavi also encourages recipient countries to help pay for their vaccines and to “graduate” from the program altogether once they can afford to do so. This isn’t always easy but is a laudable approach, not just handing out cash but focusing on the future.

Gavi is a worthy investment for the United States. The sums are relatively small, and the potential returns are significant.