The World Health Organization says global production of vaccines for pandemic flu will be "substantially less" than the previous maximum forecast of 94 million doses a week.
WHO spokesman Gregory Hartl says the number of doses produced in a year will fall short of the 4.9 billion doses the global health body previously hoped could be available.
Hartl says production will be lower because some manufacturers are still turning out vaccines for seasonal flu.
He told reporters in Geneva on Friday that production problems have also reduced the weekly output of pandemic vaccine.
WHO says that in theory all the world's 6.3 billion people should receive at least one dose of vaccine against the pandemic strain of H1N1, also known as swine flu.