Health authorities in south China's Guangdong Province have sealed off almost 20,000 doses of children's vaccines made by the US drug company Merck over contamination fears.

Health authorities across the province have bought 26,340 doses of PEDVAXHIB from Merck since November, 7,120 of which had been sold, and the rest had been sealed off, said a spokesman with the Guangdong Provincial Food and Drug Administration on Friday.

"No reports of adverse reactions to the vaccines have been received," the spokesman said.

The administration was working with the provincial health department to monitor reports of adverse reactions among children who had received the vaccines, he added.

The New Jersey-based company announced on Wednesday that it had initiated a voluntary recall of 11 lots of its Haemophilus influenza type B vaccine, PEDVAXHIB, and two lots of its combination Haemophilus influenza type B/ hepatitis B vaccine, COMVAX.

The affected doses were distributed from April 2007, it said.

"Merck is conducting this recall because it can not assure sterility of these specific vaccine lots. The potential contamination of these specific lots was identified as part of the company's standard evaluation of its manufacturing processes. Sterility tests of the vaccine lots that are the subject of this recall have not found any contamination in the vaccine," the company said in a statement on its website.

PEDVAXHIB is indicated for routine vaccination against invasive disease caused by Haemophilus influenza type b in infants and children two to 71 months of age. PEDVAXHIB should not be used in infants younger than six weeks of age, Merck said.

The most frequently reported adverse reactions were fever, irritability, sleepiness, and soreness, redness or inflammation, swelling or hardening of the skin around the injection site, as well as unusual high-pitched or prolonged crying, diarrhea, vomiting, crying, pain, infection or inflammation in the ears, a rash, and upper respiratory infection, it said.

(Xinhua News Agency December 15, 2007)