Security and immunogenicity of an acellular pertussis vaccine in premature infants. an acellular or a whole-cell pertussis vaccine. Preterm infants are at high risk of infections, and this infection is more severe and is associated with a higher morbidity and mortality than it is in infants born at full term (11, 26). The American Academy of Pediatrics therefore recommends immunizing preterm infants at their chronological age with the same vaccine routine as that recommended for full-term infants (22). These recommendations initially were based on antibody titers measured in studies performed on small numbers of infants who experienced received whole-cell pertussis vaccines (Pw) (2, 3, 10). Recent studies with the acellular pertussis vaccines (Pa) have confirmed that preterm infants mount antibody responses to the vaccine antigens, with titers in preterm infants reported to be lower (23) or comparable (17, 24) to those obtained in full-term infants. However, these studies assessed only the humoral immune responses, although protection against pertussis relies both on humoral and on cellular Th1-type immune responses (1, 15, 16, 18). Until recently, doubt existed about the ability of infants to develop a specific Th1-type immune response and therefore GSK461364 adequate immune responses to an early administration of a vaccine. Infants most often are considered relatively deficient in their capacity to secrete GSK461364 gamma interferon Rabbit polyclonal to Catenin alpha2 (IFN-) (19, 25). However, some exceptions have been reported, including the ability to secrete IFN- in response to the major antigens during contamination (14) or after vaccination (13, 5), indicating that infants are able to mount both antibody-specific and antigen-specific IFN- responses upon the infection or administration of pertussis vaccines. To our knowledge, in contrast to infants given birth to at term, no data on the early cellular immune responses of preterm infants after the administration of the primary series of pertussis vaccines have been reported yet. Therefore, we do not know whether preterm infants are able to mount adequate specific immune responses to an early administration of a vaccine. In the context of the current resurgence of infections, such knowledge should help to offer the best vaccination strategy for preterm infants. We therefore assessed here the specific cellular immune responses, together with the humoral responses, in preterm infants with very low gestational age (VLGA; given birth to at 31 weeks) that have received their first three doses of pertussis vaccines at their chronological ages. Immune responses induced by a Pa vaccine were compared to those induced by a Pw vaccine. MATERIALS AND METHODS Infants included in the study. Forty-eight premature infants were included in this study and were vaccinated against at their chronological age according to the Belgian GSK461364 vaccination recommendations at the time of the study, between 2001 and 2004. They were vaccinated at 2, 3, and 4 months of age with one of two tetravalent diphtheria-tetanus-pertussis-polio vaccines used at that time in Belgium, the Pa vaccine Tetravac or the Pw vaccine Tetracoq (both vaccines from Sanofi Pasteur, Lyon, France), combined with a lyophilized type b vaccine, as explained previously (4). As the recommendations in Belgium to administer Pa vaccines instead of Pw vaccines were implemented in 2001, we had the opportunity to compare two groups of infants receiving for their first three vaccine doses either the Pw (= 24) or the Pa (= 24) vaccine. The infants were enrolled at two different hospitals, the H?pital Erasme and the Centre Hospitalier Inter Rgional Edith Cavell. The ethical committees of both hospitals approved the study, and all of the infants’ parents gave their knowledgeable GSK461364 consent. All of the infants were given birth to at VLGA (before 31 weeks of gestational age, with a mean gestational age at birth of 28 weeks [range, 25 to GSK461364 30 weeks]). This age was determined by the known date of the last menstrual period and/or an early ultrasonogram. None of them were HIV positive, and they were not given birth to from HIV-positive mothers. They all were breastfed in the beginning, and 56% of them still were breastfed at discharge from your neonatal intensive care unit. Twenty-three of 48 infants received steroids during the neonatal period (intravenously [i.v.] for 15 of them and by inhalation for 18 of them, with 10 receiving both i.v. and inhaled corticosteroids). For the i.v. route, the last dose was administered at least 2 weeks before their first vaccine dose. Seventeen of 48 infants experienced severe infections.