ICAAC: Pertussis Vaccine Given at Birth Boosts Immune Response

CHICAGO, Sept. 21 -- Infants vaccinated against pertussis at birth have a powerful immune response that outstrips the immunity seen in babies vaccinated on the normal schedule, a researcher said here.

That finding in a small pilot study opens the door to earlier vaccination of infants against whooping cough, according to Nicholas Wood, MBBS, of the National Center for Immunization Research and Surveillance in Westmead, Australia.

As in the U.S., the standard schedule for pertussis vaccination in Australia includes three shots at two-month intervals, starting at two months of age, Dr. Wood reported at the Interscience Conference on Anti-microbial Agents and Chemotherapy.

"Pertussis in infancy is particularly nasty, so if we can prevent it, that's great," he said.

Indeed, he noted, most cases of pertussis in infancy occur before the age of four months, when the normal vaccination schedule has only just begun. Because of that, Dr. Wood and colleagues wondered if the immunization process could begin earlier.

It was not clear at the start, he said, whether the immature immune system of a newborn would respond to the vaccine. And it was also uncertain whether antibodies derived form the mother would interfere.

To answer those questions, they enrolled 76 newborns and randomized them into three groups:

• The control group of 26 babies received only the standard Hepatitis B vaccine at birth.
• A second group of 23 infants received the hepatitis vaccine and acellular pertussis vaccine at birth.
• The third group of 27 infants received hepatitis and acellular pertussis vaccines at birth, followed by another acellular pertussis shot at one month.

All of the infants got the usual DTPa-HBV-IPV-Hib and pneumococcal vaccines at two, four, and six months of age, he said.

The result was that some infants had five doses of pertussis vaccine by the age of eight months, some had four, and some only had three. The immune responses to pertussis toxoid, filamentous hemagglutinin, and pertactin were measured at birth, and two, four, six and eight months.

Analysis showed that all of the infants -- regardless of age -- had an immune response to the vaccine, Dr. Wood said. Moreover, he said, those with the five doses had a higher immune response than those who got four or three.

In fact, among infants getting the five-dose regimen, the immune response at two months was significantly higher (at P