HONG KONG: Local health authorities say the city's stock of human swine flu vaccines is unrelated to vaccine stocks in the US that have become the subject of a recall.

Secretary for Health York Chow said the recalled vaccines in the US were produced at a different factory from the 1.5 million doses delivered to Hong Kong from a European production line.

"Those we have ordered come from France and comply entirely with standards required," Chow said. "It is quite safe and effective for Hong Kong to continue with the vaccinations."

In the US, four lots containing more than 750,000 doses of swine flu vaccine for children and infants, manufactured by Sanofi Pasteur, were recalled after routine tests showed the vaccines had lost potency. The vaccines had met standards set by the manufacturer and the US government at the time of shipment. By the time the lots were delivered, Sanofi Pasteur discovered the vaccines had diminished their potency.

Antigen levels in samples of Sanofi Pasteur's H1N1 vaccine for children aged six months to three years were found to have declined after being shipped and the manufacturer is investigating the cause, according to the US Centre for Disease Prevention.

Antigens are the components in vaccines that elicit the immune system's response which builds the body's resistance to a virus.

Chairman of the Hong Kong Medical Association Tse Hung-hing said it was likely the drop in antigen levels was due to production methods rather than storage or shipping factors.

"We don't know whether the US production line added adjuvant to the vaccine. Some vaccines have adjuvant added because it increases the antigenic response so you don't need to use as much antigens to get the same reaction. This also allows companies to produce a larger amount of vaccine with the same dose of antigen," Tse said.

He added Hong Kong's swine flu vaccine supply does not have added adjuvant.

Human swine flu vaccines have been distributed to more than 80 million people worldwide, Tse said, adding side effect and failure rates were no different from vaccines for the seasonal flu.

For every 10,000 doses of vaccines administered, only one report of adverse effects had been logged, a WHO spokesman said.

Of every 100 reports of adverse effects, five are serious cases such as death, he added.

According to WHO data, more than 9,596 people have died globally since the H1N1 virus appeared in April.

The city will begin a large-scale vaccination next Monday that will cover the elderly, youngsters, pregnant women, the chronically ill and medical workers.

(HK Edition 12/17/2009 page1)