The World Health Organisation says it has reached a framework agreement to ensure all countries share samples of the deadly H5N1 strain of bird flu.
Indonesia and China have been reluctant to provide samples, fearing the vaccines produced may be too expensive.
The agreement aims to ensure that an up-to-date vaccine can be produced and that affected countries can afford it.
A WHO official said the agreement, due to be adopted on Wednesday was "a big step forward in virus sharing."
Although experimental vaccines based on the H5N1 virus exist, in order to ensure that any new vaccine would work, it must be based on the latest strain of the virus.
Indonesia - one of the countries most affected by the avian influenza outbreak - only recently began sharing its latest strain samples again, having blocked them since December.
It had argued that the pharmaceutical companies would use the samples to produce a commercial vaccine that was beyond the country's economic reach.
Health minister Siti Fadillah Supari said last week that developing countries sought a fair share of the commercial benefits derived from the H5N1 samples they provide.
But WHO Director-General Dr Margaret Chan has accused countries that refused to provide timely samples of crippling the fight against a possible flu pandemic.
News of the deal emerged as Ghana reported that it had found a second confirmed case of the H5N1 virus in the centre of the country, some distance from the first case, discovered at the beginning of May.
Since the H5N1 virus emerged in South East Asia in late 2003, it has claimed more than 180 lives around the world.
Indonesia has been hardest hit, with more than 70 deaths.
Scientists fear the virus could mutate to a form which could be easily passed from human to human, triggering a pandemic.