Vaccine 20 (2002) 826–837 Maternal immunization with pneumococcal polysaccharide vaccine in the third trimester of gestation  Flor M. Munoz a,b,∗ , Janet A. Englund b,1 , Coni C. Cheesman a , Maurizio L. Maccato b,c , Phillip M. Pinell b,c , Moon H. Nahm d , Edward O. Mason b , Claudia A. Kozinetz b , Rachel A. Thompson c , W. Paul Glezen a,b a Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA b Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA c Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX 77030, USA d University of Rochester, Rochester, NY, USA Received 7 June 2001; received in revised form 31 August 2001; accepted 31 August 2001 Abstract In a randomized, double blinded study, 23-valent pneumococcal polysaccharide vaccine (PSV) or conjugate Haemophilus influenzae type b (HbOC) vaccine was administered to 60 healthy women in the third trimester of gestation. Total IgG, IgG1, and IgG2 antibodies to pneumococcal serotypes 6B, 14, 19F and 23F were measured by ELISA in mothers prior to immunization, at delivery and 7 months after delivery, and in infants at birth (cord blood), 2 and 7 months after delivery. IgA was evaluated in breast milk at 2 and 7 months, and op- sonophagocytic activity in cord blood. PSV was safe and immunogenic in pregnant women. Transplacental transmission of vaccine-specific antibodies was efficient. Maternal immunization with PSV resulted in significantly higher concentrations of pneumococcal antibodies in infants at birth and at 2 months of age, and greater functional opsonophagocytic activity of passively acquired IgG antibody. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Pneumococcal vaccine; Maternal immunization; Opsonophagocytosis 1. Introduction Streptococcus pneumoniae is the leading cause of inva- sive bacterial infections in young children throughout the world [1,2], causing bacteremia, meningitis, pneumonia, oti- tis media, sinusitis, and other complications of respiratory tract infections. The rate of infection is greater for children under 2 years of age, reaching rates as high as 228 cases per 100,000 in those 6–12 months old [1–3]. The greatest mor- tality is observed in children with invasive disease, where case fatality rates are as high as 15–20% [1,2]. The devel- opment of resistance to antimicrobials in as much as 35%  This study was presented in part at the 37th Annual Meeting of the Infectious Diseases Society of America, November 1999, Philadelphia, PA, Abstract no. 639. The content of this publication does not necessarily reflect the views or policies of the US Department of Health and Human Services, nor does the mention of trade names, commercial products, or organizations imply endorsement by the US government. ∗ Corresponding author. Tel.: +1-713-798-5248; fax: +1-713-798-6802. E-mail address: florm@bcm.tmc.edu (F.M. Munoz). 1 Present address: Section of Infectious Diseases, Department of Pediatrics, University of Chicago, Chicago, IL, USA. of S. pneumoniae isolates in some regions [4] adds to the difficulty of treatment of diseases caused by this organism, and emphasizes the need for a preventive approach. Until recently, vaccines available to prevent S. pneumo- niae infection and disease in children in the US were the 14- or 23-valent pneumococcal polysaccharide vaccines, both relatively poorly immunogenic and not licensed for use in children less than 2 years of age [3]. A seven-valent protein–polysaccharide conjugate pneumococcus vaccine is now approved and recommended in the US for immuniza- tion of infants in the first year of life, beginning as early as the second month of life [5,6]. Routine utilization of this vaccine could substantially reduce the impact of pneumo- coccal disease in immunized children [3], but is unlikely to have a direct effect in the morbidity and mortality of the youngest infants, particularly those under 3 months of age. Other populations at risk are non-immunized infants and those for whom the conjugate vaccine is not available, as in most countries in the developing world [3,7]. In these circumstances, immunization of women during pregnancy with the pneumococcal polysaccharide vaccine is a poten- tial alternative approach to provide protection to young 0264-410X/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved. PII:S0264-410X(01)00397-8