Background: Infants less than 3 months of age are at highest risk of hospitalization and death from pertussis. Several studies have examined antibody responses to pertussis vaccines at birth but no previous study has evaluated 2 doses of monovalent acellular pertussis vaccine (aPV) before 2 months of age.
Methods: Seventy-six newborns were randomized at birth to 3 groups–aPV at birth and 1 month, aPV at birth, and control. All infants received hepatitis B vaccine (HBV) at birth followed at 2, 4, and 6 months by a combination vaccine including aPV, diphtheria, tetanus, Haemophilus influenzae type b (Hib), hepatitis B, polio antigens and 7 valent conjugate pneumococcal vaccine. IgG antibody responses to pertussis toxoid (PT), filamentous hemagglutinin (FHA), and pertactin (PRN) were measured in maternal serum and in infants at 2, 4, 6, and 8 months of age. Antibody responses to hepatitis B, diphtheria, tetanus, and Hib were measured at 8 months only. A parental diary and active telephone follow-up occurred for 7 days after each vaccination.
Results: The aPV birth dose was well tolerated. By 2 months of age, 22 of 25 (88%) of 2 dose recipients had detectable IgG antibody to PT (IgG PT) compared with 9 of 21 (43%) who received a birth dose only and 3 of 20 (15%) of controls. Infants in the 2 dose group had a geometric mean concentration (GMC) of IgG PT of 16 ELISA units per mL (EU/mL), 95% CI: 11 to 25, significantly higher than birth dose only (5 EU/mL, 95% CI: 3–8) and controls (3 EU/mL, 95% CI: 2–5). At 8 months of age, following 5, 4, and 3 doses of aP-containing vaccine, respectively, IgG PT had plateaued but IgG to FHA and PRN increased with successive doses. There was a trend to lower antibody responses for hepatitis B and Hib with higher numbers of Pa doses.
Conclusion: These data suggest that aPV at birth and 1 month induces significantly higher IgG antibody against pertussis antigens by 2 months of age without reducing subsequent pertussis antibody responses. Larger and more detailed studies of aPV from birth are needed to evaluate other antibody responses and the potential of this approach to reduce death and morbidity from Bordetella pertussis infection in the first 3 months of life.
From the *National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, The Children's Hospital at Westmead and the University of Sydney, New South Wales, Australia; †Kids Research Institute, The Children's Hospital, Westmead, Sydney, South Wales, Australia; ‡Faculty of Medicine, The University of Sydney, New South Wales, Australia; §Vaccine and Immunology Research trials Unit, The University of Adelaide and Women's and Children's Hospital, Adelaide, Australia; and ¶Faculty of Medicine, The University of Otago, New Zealand.
Accepted for publication August 17, 2009.
Supported by a grant from the Financial Markets Foundation for Children, Australia (S112 – 2004). GlaxoSmithKline provided the investigational aPV and performed all serologic assays. Engerix and Infanrix hexa are trademarks of the GlaxoSmithKline group of companies; Prevnar is a trademark of Wyeth Pharmaceuticals Inc.
Address for correspondence: Nicholas Wood, National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases (NCIRS), Locked Bag 4001, Westmead, New South Wales 2145, Australia. E-mail: email@example.com.
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