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TABLE P.3 Maternal GBS Infections

 

Vaginal Deliveries

Caesarean Sections

Total number (%) of deliveries estimated for 1984

3,182,203

(84%)

606,134

(16%)

Number of cases of endometritis/ parametritis

127,288a

 

96,981b

 

Number caused by GBS (20%)

25,458

 

19,396

 

Number of cases of bacteremia

 

 

15,153c

 

Number caused by GBS (20%)

 

 

3,031

 

aEstimated to be 4 percent of vaginal deliveries.

bEstimated to be 16 percent of caesarean sections.

cEstimated to be 2 to 3 percent of caesarean sections.

Vaccine Target Population

The target population for protection is the newborn infant. The target population for active immunization would be pregnant women, although immunization might take place prior to pregnancy. Conjugation of the polysaccharide antigen with a protein carrier might increase the antigenicity of a streptococcus group B vaccine. The native polysaccharide antigens already have been shown to be immunogenic in nonpregnant adults. The incidence of reactions is relatively low, less than that associated with the pneumococcal vaccine, in addition, Hemophilus influenzae type b polysaccharide vaccine has been used in pregnant women without significant complications (Hill, 1983). However, a foreseeable problem in vaccinating such a target population would be the usual hesitancy to expose pregnant women to exogenous substances.

Suitability for Vaccine Control

Theoretically, a program of active immunization aimed at pregnant women would have the best prospects of controlling early-onset and late-onset GBS disease. Successful vaccine control by this approach, will require elicitation of antibodies capable of crossing the placenta to protect the fetus. Alternative strategies include passive immunization of the newborn, which would not prevent early-onset disease that develops in utero, and various forms of chemoprophylaxis, which would be unlikely to prevent late-onset disease (Fischer et al., 1983). Chemoprophylaxis has been studied during pregnancy, labor, and the



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