A Pfizer spokeswoman said that the three infants also received two unrelated other vaccines as part of routine immunizations.

A Pfizer spokeswoman, Kate Robins, would not say if the company is interested in the hospital property.

A Pfizer spokeswoman referred callers to Eisai, which conducted the study.

Ms. Caprino, the Pfizer spokeswoman, said the company finances development of treatment guidelines to ensure that patients get the best possible medications.

A Pfizer spokeswoman said that "physicians should be able to express their professional discretion in making individual treatment decisions."

A Pfizer spokeswoman said all five cases had been reported to the Food and Drug Administration.

Susan Bro, a Pfizer spokeswoman, said that it was too early to speculate on how such a requirement might affect the company's advertising.

Mariann Caprino, a Pfizer spokeswoman, said the company could not comment further because the subpoena was still being reviewed.

"We are exploring our options," a Pfizer spokeswoman said last night.

"We tried to make it fun," said Erica Johnson, a Pfizer spokeswoman.