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Bordetella pertussis seroprevalence among pregnant women in the Netherlands supported maternal vaccination
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Findings from a study involving pregnant women in the Netherlands indicated a higher seroprevalence of Bordetella pertussis infection in this population than previously observed.
“Our findings emphasize once more that B. pertussis infection often remains unreported, possibly because of a subclinical course of infection or the failure to recognize or report the disease by a general practitioner,” the researchers wrote.
The researchers distributed questionnaires to 315 pregnant women at a general hospital in the Netherlands; performed serological testing on umbilical cord blood samples and maternal blood samples taken at delivery and two months after delivery and retrospectively analyzed maternal blood samples taken at 12 weeks gestational age when available.
Despite high levels of pertussis vaccination in childhood (76%), eight women had immunoglobulin G pertussis toxin levels indicative of infection during an eight-month follow-up period and another 12 had antibody levels of 50 U/mL to 100 U/mL, which indicated infection in the year prior. Among women with serologically confirmed B. pertussis infection, two reported coughing during pregnancy.
The incidence of B. pertussis infection among pregnant women observed in this study was similar to the 6.6% seroprevalence previously reported in the general population but higher than estimates from an additional study involving another subset of pregnant women, whose researchers put the rate at 1.8%.
The researchers attributed this increase to differences in study design and said that collecting maternal blood samples at three time points vs. only-cord serum increased their diagnostic yield.
Additionally, 15.7% of participants had antibody levels below the limit of detection upon delivery. “Although protective levels for antibodies against pertussis have not been established, low IgG pertussis toxin levels correlate with increased susceptibility to pertussis,” the researchers wrote.
They suggested that their findings favor third-trimester maternal vaccination but they called for additional safety and efficacy research to address concerns about potential adverse events.
Nooitgedagt JE. Clin Infect Dis. 2009;49:1086-1089.