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AAP Grand Rounds 21:1 (2009)
© 2009 American Academy of Pediatrics

Effectiveness of Maternal Influenza Immunization in Mothers and Infants

Researchers from the International Centre for Diarrheal Diseases Re search in Bangladesh (ICDDR,B) and Johns Hopkins evaluated the effectiveness of antenatal immunization with inactivated influenza vaccine (TIV) for the prevention of influenza and related illnesses in mothers and in their infants during the first six months of life.

PICO Question: Does the administration of inactivated influenza vaccine to pregnant women in Bangladesh prevent influenza illness in their infants? Question type: Intervention Study design: Prospective randomized

 

Between August 2004 and May 2005, healthy pregnant Bangladesh women in the third trimester were randomized to receive either TIV or polysaccharide pneumococcal vaccine (PPV-23). Live-born infants were randomized to immunization with either conjugated pneumococcal or Haemophilus influenzae type B vaccine.

Mothers were followed from two weeks after immunization through pregnancy and delivery, and interviewed weekly for 24 weeks after birth to assess for illnesses in them or their infants. A physician examined all infants reported by mothers to have a febrile respiratory tract infection. In infants with physician-confirmed illness, throat swabs were tested for influenza A and B antigens while influenza antigen detection test kits were available.

Among the 340 women enrolled, vaccination occurred approximately 57 days before delivery; 172 women were immunized with TIV and 168 with PPV-23. Among infants born to TIV-vaccinated mothers there were six cases of laboratory-confirmed influenza, compared with 16 cases in infants born to PPV-23-vaccinated mothers (vaccine effectiveness 63%; 95% CI, 5–85%). Respiratory illness with fever occurred in 110 infants in the maternal-TIV group and 153 infants in the PPV-23 group, resulting in a vaccine effectiveness against febrile respiratory illness of 29% (95% CI, 7–46%). Respiratory illness with any fever occurred in 77 TIV-vaccinated women and 50 PPV-23-vaccinated women (vaccine effectiveness 36%; 95% CI, 4–57%). The authors concluded that administration of TIV to pregnant women benefitted both mothers and their infants.

Commentary by Andi L. Shane, MD, MPH

Pediatric Infectious Diseases, Emory University School of Medicine, Atlanta, GA

 
Dr. Shane has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.

Key Words: influenza • immunization • prevention

Infants <24 months of age with influenza infection have more severe disease with greater mortality than older children.¹ One prevention strategy is to immunize pregnant women in the hope that type-specific transplacental or breast milk-associated antibody can ameliorate or prevent infection. Although US and international public health authorities recommend universal immunization of pregnant women, the uptake of seasonal influenza vaccine among pregnant women remains poor.²

The Mother’s Gift project is a collaboration led by the ICDDR,B to assess sequential maternal and infant immunization with pneumococcal vaccines in Bangladesh. Due to the design of the trial, the efficacy of antenatal immunization against influenza could be assessed.

Although TIV was effective in preventing influenza infections in infants (63%), and fever and respiratory symptoms in infants (29%) and mothers (36%), the associated confidence intervals were wide: 585%, 746%, and 457%, respectively. The small number of patients, shortage of influenza antigen detection kits, and relative infrequency of influenza infection all likely contributed. The sensitivity of the detection kits used is only approximately 70%.³

While this should not affect the relative effectiveness rate of the vaccine, the absolute incidence may be underestimated. Use of a control group who received PPV23 rather than an inactive compound may have decreased the effectiveness results by reducing febrile and respiratory symptoms and therefore decreasing clinic visits. The study was further limited by inadequate statistical power to assess less frequent manifestations of influenza infection, including hospitalization.

These results support maternal immunization to prevent influenza infections during the first six months of life. The findings have particular relevance to tropical countries where influenza viruses circulate perennially. In regions of the world with limited financial resources and access to medical care, antenatal immunization systems are already in place. If further large-scale trials demonstrate similar effectiveness, maternal influenza vaccination could be added to existing antenatal immunization programs. Even in resource-rich areas, such a finding would support immunization of pregnant women against seasonal influenza for both their own health and their child’s.

Reference

1. Izurieta HS, et al. N Engl J Med. 2000;342:232–239.[Abstract/Free Full Text]
2. CDC. MMWR. 2008;57(No. RR-7).
3. Rodriguez WJ, et al. Pediatr Infect Dis J. 2002;21:193–196.[CrossRef][Medline]

This Article Extract Full Text (PDF) Take the CME quiz: Vol. 21 No. 1, January 2009 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Shane, A. L. Search for Related Content PubMed Articles by Shane, A. L.