The recall of a routine vaccine for babies due to contamination risks could trigger a shortage and likely will alarm parents, but officials said there is no known health threat.

The recall announced Wednesday covers roughly 1.2 million doses of the vaccine against Hib, which causes meningitis, pneumonia and other serious infections, and a combination vaccine for Hib and hepatitis B. The Hib vaccine is recommended for all children under 5 and is usually given in a three-shot series, starting at 2 months old.

Drugmaker Merck & Co. produces about half of the nation's annual supply of 14 million doses of Hib vaccine.

Merck recalled the lots after this week identifying a sterility problem in a Pennsylvania factory. It said sample vials from the recalled lots, tested before shipment, were not contaminated but the company could not assure sterility of the entire lots.

"The potential for contamination of any individual vaccine is low," said Kelley Dougherty, a spokeswoman for the Whitehouse Station-based company.

Dr. Julie Gerberding, head of the Centers for Disease Control and Prevention, echoed that in a news conference.

"This is not a health threat in the short run, but it is an inconvenience," she said.

Barbara Kuter, Merck's head of pediatric medical affairs, told The Associated Press that the company will not be able to supply any vaccine for at least nine months.

"Manufacture of vaccines is pretty complicated, and we have to basically make some changes in the process," then get approval from the Food and Drug Administration before resuming production and shipments, Kuter said. Merck hopes to restart production next fall, she said.

"It's likely that there's going to be a shortage of this product," Kuter said, adding that the impact on the public is unclear.

Donna Cary, spokeswoman for Sanofi Pasteur, the only other company making the vaccine for the US, said it was too soon to say whether it can boost production. The company, a unit of Paris-based drugmaker Sanofi-Aventis SA, makes an Hib vaccine in France that is distributed both to the US and other countries.

"We're looking at what we can add and we're working closely with the CDC on this," to see whether some vaccine could be shifted to the US from other countries, Cary said.

Health officials said they already are talking about prioritizing shots for American Indian and Alaska Native children, who are considered at higher risk for Hib-caused illnesses, said Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases.

It was unclear how many of the 1.2 million doses were administered to children.

The recalled doses, distributed beginning in April, are considered potent, so revaccinations won't be needed, Schuchat said.

Should the vaccine later prove contaminated, health officials believe most children will experience, at worst, skin irritation around the shot site. Problems could be worse for children with weakened immune systems.

Any problems would have appeared within a week of vaccination, Schuchat said, and there have been no such reports.

The contamination was on unspecified equipment used in making the vaccine. Kuter said a sterility test during a routine evaluation of Merck's West Point, Pa., vaccine plant determined that the equipment was contaminated with a common bacterium called Bacillus cereus, or B. cereus.

It is a spore-making microorganism commonly associated with food poisoning and causes diarrhea and vomiting in people who eat contaminated foods.

The recall is likely to heighten a debate over childhood vaccines, their safety and whether too many are required. Some parents are distrustful and suspect some vaccines of being linked to autism, although scientific studies have not shown a connection.

This week, New Jersey took a controversial step toward becoming the first state to require flu shots for preschoolers after a health advisory board backed new vaccine requirements over opposition from some worried parents.

Merck is one of the few drugmakers that make vaccines. Company representatives could not immediately say how much revenue the Hib vaccine produces.

While the company took a black eye with its September 2004 withdrawal of painkiller Vioxx due to increased heart attack risk, it has been performing well recently. It gave an upbeat assessment Tuesday in its annual briefing for analysts.

Five weeks ago, Merck reached a deal to settle up to 50,000 Vioxx lawsuits for $4.85 billion, an amount expected to save the company millions in trial costs.

Its stock price has more than recovered from its post-Vioxx slump, a two-year-old restructuring plan is going well, and profits are up. Merck posted a 62 percent increase in its third-quarter profit as revenues jumped 12 percent.

The company also has had an impressive seven new products approved for US sale in the last two years, including three vaccines.

Merck shares fell 68 cents Wednesday to close at $59.72 before the recall announcement. The shares fell 12 cents in after-hours trading.

(Agencies via China Daily December 14, 2007)