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Immunogenicity of an Inactivated Hepatitis A Vaccine in Infants and Young Children

Bell, Beth P. MD*; Negus, Susan RN; Fiore, Anthony E. MD*; Plotnik, Julia RN; Dhotre, Kathy Boaz MPH*; Williams, James CNP; Shapiro, Craig N. MD*; McMahon, Brian J. MD

The Pediatric Infectious Disease Journal: February 2007 - Volume 26 - Issue 2 - p 116-122
doi: 10.1097/01.inf.0000253253.85640.cc
Original Studies

Background: Infants with passively transferred maternal antibody, born to mothers immune to hepatitis A virus (HAV), have a blunted response to hepatitis A (HA) vaccine. We compared HA vaccine immunogenicity among infants born to immune and susceptible mothers, vaccinated on different schedules.

Methods: Infants were randomized into 3 groups, each receiving 2 doses of 720 EL.U. of HA vaccine (HAVRIX; Glaxo SmithKline): group 1 at ages 6 and 12 months, group 2 at ages 12 and 18 months and group 3 at ages 15 and 21 months. We determined mothers’ antibody to HAV (anti-HAV) status and infants’ anti-HAV concentrations at the first vaccine dose (baseline) and at 1, 7 and 12 months thereafter. All were tested at age 13 months for responses to recommended routine vaccinations administered during infancy.

Results: Of 248 participants, 140 were born to HA-susceptible mothers and 108 to immune mothers. At baseline, 34 of 36 (94%) group 1, 5 of 34 (15%) group 2 and one of 38 (3%) group 3 infants born to immune mothers were seropositive. By month 7, all participants in all groups were seropositive except group 1 infants born to immune mothers (34 of 36 [94%], seropositive). In group 1, peak geometric mean concentrations between infants born to immune (794 mIU/mL) and susceptible (2083 mIU/mL) mothers were significantly different. Across groups, peak geometric mean concentrations were similar among infants born to susceptible mothers (3166 mIU/mL, group 2; 3153 mIU/mL, group 3). Among infants born to immune mothers, the difference between groups 1 and 3 (2715 mIU/mL) was significant. There were no differences in responses to routine vaccinations.

Conclusions: HA vaccine is immunogenic among infants born to HA-susceptible mothers and those born to immune mothers and vaccinated beginning ≥12 months old. Passively transferred maternal antibody persists for at least 6 months and results in a blunted response to HA vaccination.

From the *Division of Viral Hepatitis, Centers for Disease Control and Prevention, Atlanta, GA; the †Liver Disease and Hepatitis Program, Alaska Native Tribal Health Consortium; and the ‡Anchorage Neighborhood Health Center, Anchorage, AK.

Accepted for publication November 10, 2006.

Address for correspondence: Beth P. Bell, MD, MPH, MS G-37, CDC, 1600 Clifton Rd. NE, Atlanta GA 30033. E-mail: bzb8@cdc.gov.

© 2007 Lippincott Williams & Wilkins, Inc.