Seroprevalence of diphtheria, tetanus and pertussis antibodies and Tdap vaccination in pregnant women in Greece – A cross- sectional study

Objectives

We performed a cross- sectional study in two maternity hospitals in Athens, Greece between 2017 and 2019 assessing seroprevalence and Geometric Mean Titres (GMTs) of diphtheria, pertussis and tetanus antibodies in pregnant women and recorded adherence to Greek National Immunization Program (NIP) regarding Tdap vaccination in pregnancy.

Methods

Blood samples were collected from women in labour and anti- diphtheria, tetanus and pertussis toxin IgG antibodies were measured by Elisa kits. Seropositivity was defined as anti-diphtheria and anti- tetanus toxin IgG levels ≥0.1, and anti- pertussis >50 IU/mL. Seroprevalence and GMTs were calculated according to demographic factors. Tdap vaccination before and during pregnancy was self-reported by study participants.

Results

We analysed 253 blood samples and paired questionnaires. Seropositivity was 57.7 % for diphtheria. The lowest rate (38.2 %) was observed in the youngest age group (≤25 years). Increasing age was associated with higher seroprevalence (p = 0.036). 12.5 % of women were seropositive against pertussis. Most were seropositive for tetanus (92.7 %). Anti-pertussis GMTs were 16.98, anti-diphtheria 0.13 and anti- tetanus GMTs 0.63 IU/mL. Women born in Greece and with higher educational level had higher antibodies against tetanus (p = 0.004 & 0.004 respectively). 3/253 (1.2 %) of women assessed reported Tdap vaccination during pregnancy.

Conclusion

Seropositivity rates were low for diphtheria and pertussis among pregnant women. In addition, less than 2 % were vaccinated with Tdap despite recommendation by Greek NIP. Therefore, many infants end up unprotected during the first months of life. Our study highlights the urgent need for national campaigns targeting to completion of childhood immunization and information of the public about safety and importance of Tdap vaccination in pregnancy.