Moreover, the fact that premature infants have lower levels of maternal antibodies than full-term infants may be an additional factor involved in the better humoral immune response to vaccination [19] and [20]. In the same way, Baxter et al. referred that 100% and 98.3% of 121 premature infants born less than 32 weeks of gestation developed, respectively, a minimum and optimum antibody levels after a 3 dose primary series of tetanus vaccine [21]. However, despite these factors, the premature infants

analyzed in the present study had lower levels of antibodies. This finding suggests the influence of premature birth and/or possible factors PFI-2 associated with a lower immune response to vaccination or a faster decay in antibody levels resulting from the primary vaccination in premature infants in comparison to those born at full term [22]. It is possible that the immune response to the tetanus vaccine in the first six months of life was lower among the infants born prematurely, especially those born with a gestational age of less than 32 weeks, in comparison

to those born at full Venetoclax molecular weight term, as described by other authors [5]. These results are in agreement with data described in the literature stating that immune response in premature infants may be lower in the first six months of life due to the lower number of circulating T and B lymphocytes and T helper cells as well

as the lower CD4/CD8 ratio in comparison to children having been born at full term [23]. In the present study, the premature group was recruited among children born prematurely with a birth weight of less than 1500 g and the control group was composed of children born at full term, adequate for gestational age, with no clinical complications in the neonatal period and discharged from hospital by four days of life. Moreover, the control group had children within the ideal weight range and a good breastfeeding index until six months of age, whereas 77% of the premature group had been born at a gestational age of less Endonuclease than 32 weeks, had a high rate of hospitalization following discharge from the neonatal unit and a low breastfeeding index. Nonetheless, the humoral response to the tetanus booster was similar between groups and cell immunity was similar between groups at 15 and 18 months of age. These findings show that the two groups had a similar good memory response after a booster dose at 15 months after having received a 3 dose primary series vaccine against tetanus. Vermeulen et al. compared 48 premature infants who were born at less than 31 weeks of gestational age after vaccination at 2, 3, and 4 months of chronological age with an acellular or a whole-cell tetravalent diphtheria–tetanus–pertussis–polio vaccine.