GENEVA (Reuters) - Drug makers can only produce enough H1N1 vaccine each year for half the planet and each country will have to decide who should get the limited supplies, the World Health Organization (WHO) said Thursday.
The H1N1 vaccine looks to be as safe as the regular flu shot it said in a statement estimating that drug makers worldwide can produce an estimated 3 billion doses per year.
A single dose should be enough to give immunity to healthy adults and older children from the virus commonly known as swine flu, it said.
The WHO later said it was looking into an unpublished Canadian study indicating that a seasonal flu shot could increase the risk of catching the H1N1 virus. No other researchers had reported such findings, it said.
Dr. Marie-Paule Kieny, director of WHO’s initiative for vaccine research, said clinical trials had shown the vaccines being developed to be safe. Yields were better than previously thought though not quite as good as for seasonal flu.
“Vaccine development is on track,” Kieny told reporters, noting that China had begun immunizing its population and Hungary was expected to follow suit next week.
“These vaccine trials have given actually very good news. They have demonstrated that it is possible to reach a protective level of immunity with a single dose of vaccine, at least in most of the population,” she said.
But drug companies had limited capacity to increase output to cover the planet’s 6.8 billion population, according to the United Nations agency whose previous projection for global production capacity was close to 5 billion doses.
AS SAFE AS SEASONAL FLU SHOTS
“Outcomes of trials completed to date suggest that pandemic vaccines are as safe as seasonal influenza vaccines,” WHO said.
“However, even very large clinical trials will not be able to identify possible rare events that can occur when pandemic vaccines are administered to many millions of people,” it said.
Kieny said it was the responsibility of national health authorities to decide who gets the limited supplies, but said that vaccination programs should not be mandatory.
“The choice of population to be vaccinated is a national prerogative. Each country will have to take a decision in view of its own epidemiologic and national characteristics,” she said.
However, the WHO strongly recommended that health care workers -- who make up an estimated two percent of the global population -- are vaccinated, she said.
The WHO advised countries to closely monitor the vaccine’s safety and report “adverse events.” This was vital to determine whether changes in vaccination policies were needed.
Possible side effects are expected to be similar to those with seasonal flu vaccines, including soreness or swelling at the injection point and fever, headache, muscle or joint aches. These symptoms should be mild and last 1-2 days.
Most rich nations have contracts with drug makers to obtain enough vaccine to cover their entire populations, it said.
But most low- and middle-income countries lack the financial resources to compete for an early share of limited supplies, which in such countries would depend mainly on donations.
The WHO said it would begin an initial distribution of some 300 million doses of vaccine donated by rich nations to more than 90 developing countries from November.
Leading flu vaccine makers include Sanofi-Aventis, Novartis, Baxter, GlaxoSmithKline and Solvay.
Editing by Philippa Fletcher
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