A large-scale immunization campaign against swine flu has started in the United Stats with the vaccination of 68,000 New Yorkers.

New York City''s vaccination campaign got underway in the Children''s Hospital at Montefiore. The mayor''s office said in a statement the city''s medical institutions will carry out 2 million immunizations a month in October-January, adding there will be enough doses for all New York residents.

Local media has reported that vaccination will take place on a voluntary basis, with priority given to five high-risk groups: pregnant women; children; people under 24; adults aged 25 to 64 who with asthma, diabetes and some other diseases; and medical staff who work with flu victims.

According to public polls, about one third of Americans intend to be vaccinated. Tests indicated that a single dose of the vaccine can protect a person against the A/H1N1 virus, and reports say about 195 million doses will be produced.

U.S. medics said the next outbreak of the disease is expected in October. According to federal authorities, there were 3,336 people hospitalized with suspected swine flu virus in the country as of October 3, against 76 hospitalized as of September 1.

According to the latest report from the World Health Organization, 340,000 cases of swine flu have been confirmed throughout the world and 4,100 people have died from the virus as of September 27.

The head of Russia''s health watchdog Roszdravnadzor said on Thursday that Russian scientists had developed and tested two vaccines for the virus.

"At the end of October we shall receive a live vaccine...and at the beginning of November, one more," Nikolai Yurgel said. "Before the start of the flu epidemic, Russia will have a vaccine. I think this is not a bad outcome."