TRENTON - Pediatricians rushed to stock up on a crucial baby shot yesterday, a day after vaccine manufacturer Merck announced it was recalling 1.2 million doses and suspending production.

Meanwhile, worried parents were calling doctors' offices to ask whether their children were safe if they recently received the Hib vaccine, which protects against meningitis, pneumonia, and other life-threatening and disabling bacterial diseases. Parents were told that there was virtually no chance of anything but swelling and redness around the injection, which would have happened long ago.

Health officials are still scrambling over how to address the shortage, caused by a problem at Merck's plant in West Point, Pa.

They are weighing options to stretch the supply of Hib vaccine from the only other manufacturer, Sanofi Pasteur, and waiting to hear if it can boost production or shift doses here from overseas.

The American Academy of Pediatrics is advising its 60,000 members to try to order now from Sanofi Pasteur, and if they run short, to delay the booster shot usually given at 12 to 15 months.

Merck supplies about half the 14 million doses of Hib vaccine used in the United States each year. It said that in addition to the doses it recalled as a precaution - roughly four months of production - it has quarantined nearly a year's worth of possibly suspect doses and does not expect to supply more until at least next October. That means two years of its normal production is unavailable.

Merck has said it initiated the recall as a precaution because a routine test in October found bacterial contamination on production equipment; none has been found in a vaccine.

The company quarantined all Hib vaccine produced since the last "clean" sterility test, in November 2006. Further checks showed the most likely cause of the problem was a manufacturing change made in July 2006, so it recalled all doses made between July 2006 and November 2006. They were distributed beginning in April.