The World Health Organization on Thursday ruled out swine flu vaccine as the cause of death in 41 people who had received the flu shot.
WHO vaccines chief Marie-Paule Kieny said deaths investigated by health authorities so far weren't caused by the vaccine. Further deaths were still being investigated, she added.
WHO spokeswoman Nyka Alexander said the 41 deaths examined in connection with the vaccine occurred in six countries. She was unable to say how many deaths were still being examined.
Health experts have been closely monitoring the safety of the new pandemic vaccine that is being given to millions of people worldwide.
Decades of safe influenza inoculations mean specialists aren't expecting problems with the swine flu shot, because it's made the same way as the regular winter flu vaccine.
In some European countries, including Germany and Switzerland, there has been public concern whether the use of adjuvants in vaccines is safe. These additives are intended to boost the body's immune response and stretch the vaccine's active ingredient so more doses can be made.
No flu vaccines with adjuvants are licensed so far in the United States, though they are commonly used in Europe.
"The pandemic flu vaccine is as safe as seasonal flu vaccines," said Kieny, adding that vaccines against the pandemic flu strain, known as H1N1, have no more side effects than previous flu vaccines.
Out of every 10,000 doses of vaccines administered only one person develops reaction to the vaccine, she told reporters. Five out of 100 reactions are serious, she said.
Some in the U.S. have expressed concern that possible side effects could include the Guillain-Barre syndrome, a rare paralyzing condition, that was reported during the last mass vaccinations against a very different strain of swine flu in 1976.
Kieny said less than a dozen suspected cases of Guillain-Barre have been seen so far following swine flu inoculations and only a few of them may be linked to the vaccine. All patients have recovered, she added.
"What we do see is a variety of local reactions, such as pain at the injection site, swelling, redness and reactions such as fever, headache, muscle pain or fatigue," she said. Such reactions, which are common after flu shots, usually disappear after a day or two, she added.
WHO says pregnant women and people suffering from chronic diseases are at greatest risk of developing complications from the pandemic strain of flu and has urged countries to make them a priority group for vaccination.
More than 6,250 people around the world have died from swine flu since the disease was identified in April, according to WHO.