519. Influenza Immunization in Pregnancy and Infant Antibody at 4 Months
Session: Poster Abstract Session: Influenza Vaccines
Friday, October 21, 2011
Room: Poster Hall B1

Background:  Although trivalent inactivated influenza vaccine (TIV) is recommended during pregnancy, there is little data on duration of passive antibody in infants born to immunized pregnant women. Study objectives were to: 1) quantify influenza antibodies in mother-infant pairs by hemagglutination inhibition (HAI) assay at birth, 2, and 4 months, and 2) compare antibody levels in infants born to women who did and did not receive influenza vaccine in pregnancy.

Methods:  Pregnant women 18-45 years of age were enrolled from 4/10–12/10 at the University of Utah Health Sciences Center. Enrolled women were pregnant during wave 2 of the 2009 H1N1 pandemic and the 2009-10 influenza season when the predominant influenza strain in the community was pandemic H1N1. Maternal and infant sera were tested at Vanderbilt University by HAI assay for antibody to 2009 pandemic H1N1 and 2009-10 seasonal vaccine strains. Protective antibody titers were defined as > or = 1:40.

Results:  Of 27 mother-infant pairs, 41% (11/27) reported receiving seasonal vaccine and 44% (12/27) reported receiving pandemic H1N1 vaccine. 92% (11/12) received seasonal vaccine in the first trimester and 8% (1/12) in the second trimester. 83% (10/12) received pandemic H1N1 vaccine in the first trimester and 17% (2/12) in the second trimester. The proportion of infants with HAI titers > or = 1:40 to one or more influenza vaccine strain by maternal vaccine status are shown in Table 1.

Table 1. Proportion of infants with HAI titers > or = 1:40 at birth, 2, and 4 months by maternal vaccine status

Maternal Vaccine Status


(n=27 infants)

2 Months

 (n=24 infants)

4 Months

(n=22 infants)

Seasonal vaccine (n=11)




No seasonal vaccine (n=16)




Pandemic H1N1 vaccine (n=12)




No pandemic H1N1 vaccine (n=15)




*p < 0.001

Conclusion:  Infants born to women receiving seasonal vaccine in early pregnancy were more likely to have protective antibody at birth and 2 months compared with infants born to unimmunized women. Differences were not seen with pandemic H1N1 vaccine. With immunization in early pregnancy, the majority of infants had no protective antibody by 4 months. Maternal influenza vaccine in late pregnancy may afford more sustained infant protection against influenza during the first 6 months.

Subject Category: I. Adult and Pediatric Vaccines

Julie H. Shakib, DO, MPH1, Carla M. Suarez, BS1, Andrew Pavia, MD, FIDSA1, Michael W. Varner, MD1, Michael T. Rock, PhD2, Kathryn Edwards, MD, FIDSA2 and Carrie L. Byington, MD3, (1)University of Utah Health Sciences Center, Salt Lake City, UT, (2)Vanderbilt University Medical Center, Nashville, TN, (3)Department of Pediatrics, Division of Pediatric Infectious Diseases, University of Utah School of Medicine, Salt Lake City, UT


J. H. Shakib, None

C. M. Suarez, None

A. Pavia, pfizer: Consultant, Consulting fee

M. W. Varner, None

M. T. Rock, None

K. Edwards, None

C. L. Byington, Idaho Technology, Inc.: Collaborator, Licensing agreement or royalty and subcontract on NIH grant

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