The WHO says the vaccine is just one weapon against swine flu
About 100 developing nations will begin receiving donations of the vaccine against swine flu as early as November, the World Health Organization says.
Millions of doses of the vaccine against H1N1 are being donated by pharmaceutical companies.
A group of rich nations have also pledged to donate 10% of their vaccine purchases to poorer countries.
The latest figures reported to the WHO suggest more than 4,500 people worldwide have died from swine flu.
But most of the hundreds of thousands of people who have contracted the illness around the world have experienced only mild to moderate symptoms.
Countries including China, Australia and the United States are reported to have begun mass vaccination programmes after scientists worked flat out to develop a vaccine.
The WHO has long stressed the need for developing countries to get access to some doses of the vaccine if the global campaign against the virus is to be effective.
On Monday the WHO's head of vaccine research, Marie-Paule Kieny, told journalists in Geneva that about 100 low- and middle-income countries would receive donated vaccines.
"We are trying to have a first delivery starting in November," she said.
"The idea is to start with northern hemisphere countries first," she added - as winter is approaching in this hemisphere.
Dr Kieny said health workers should be among those being prioritised to receive swine flu vaccinations in the recipient countries.
She said data showed that one dose of the vaccine was likely to provide sufficient protection.
Sanofi-Aventis and GlaxoSmithKline are donating about 150 million doses of the vaccine, with an unspecified amount coming from a third company, Medimmune.
The US is thought to be among nine or 10 rich countries which have also pledged to donate a proportion of their vaccines to developing nations - though the WHO says more doses are needed.
However, the WHO says that vaccines are not the only weapon in the fight against swine flu.
It says other measures, such as school closure, avoidance of large gatherings, antibiotics and personal hygiene are also needed.