Premature infants do not face any increased risk from their first immunization, according to a study by researchers at the Western Pennsylvania Hospital, published today in the May issue of Pediatrics, the journal of the American Academy of Pediatrics.

Co-author Nilima Karamchandani, chief of neonatology at West Penn, said the results affirm the AAP's long-standing recommendation that 2-month-old babies, no matter how early they are born, should receive their diphtheria-tetanus-acellular pertussis, or DTaP, vaccine.

"We would like the babies to get their shots when AAP recommends it," Dr. Karamchandani said. "We want to inform the public as well as the doctors that it is safe."

She said some pediatricians had delayed the vaccine or cut doses because of reports of premature babies receiving their DTaP shots and then suffering higher rates of apnea, which is a cessation of breathing, and bradycardia, a slow heart rate.

The doctor said the latest study sought more objective data from bedside monitoring equipment, analyzed by independent experts.

The randomized, controlled clinical trial involved 10 hospital neonatal intensive care units treating 191 infants born at less than 37 weeks gestational age, and enrolled at 2 months of chronological age.

The babies with similar medical characteristics -- but half randomly chosen for vaccination -- were monitored, and those results were analyzed by two specialists based at different sites.

Besides West Penn, the Children's Home and Lemieux Family Center of Pittsburgh also participated as a study site.

Dr. Karamchandani said she herself has been concerned about the effect of vaccine on some premature infants. Those in the study averaged about 3¹/₂ pounds in weight.

But, although the babies continued to have prolonged episodes of apnea (16 percent) and bradycardia (58 percent) after their immunizations, the rates were not very different from the unvaccinated group -- apnea (20 percent) and bradycardia (56 percent).

Dr. Karamchandani said the babies should be protected from the diseases covered by the vaccine.

"They are in a high-risk period," she said. "They can't fight infections; they don't get antibodies from their mothers."

The study was funded by the American SIDS Institute. Premature babies are at a higher risk for sudden infant death syndrome, as well as apnea and bradycardia, Dr. Karamchandani said, although the cause of SIDS is still unknown.

"We tell parents not to smoke, put their baby on his back to sleep ..." she said. "In most SIDS cases, 75 percent, the kids never had apnea."

"We can only prove immunization is safe for babies," she said.