Beijing ? After more than a year of international pressure, China acquiesced Friday to demands that it share samples of avian influenza virus with global health authorities but rejected a report that a new vaccine-resistant strain of the disease is spreading.

China provided samples from bird flu outbreaks in 2004 and 2005 but didn’t offer samples from outbreaks this year, when the variant reportedly has flourished. The nation’s chief veterinarian, Jia Youling, said 20 samples had been delivered to the Atlanta-based U.S. Centers for Disease Control and Prevention, a research partner with the World Health Organization.

The World Health Organization’s China representative, Henk Bekedam, said he was “very encouraged” that China had offered the bird-flu virus samples, and would “follow up instantly” to press for samples isolated this year.

Global health workers require updated virus samples to prepare effective vaccines as new strains of disease emerge.