The Effect of Timing of Tetanus-Diphtheria-Acellular Pertussis Vaccine Administration in Pregnancy on the Avidity of Pertussis Antibodies

Figure 1. Fractional absolute anti-PT IgG levels by time of vaccination against pertussis in pregnancy achieved at the different ammonium thiocyanate concentrations. The quantified fractional absolute avidity levels of anti-PT IgG at 0.25 molar (M), 0.5, 1, 1.5, 2, and 3 M of ammonium thiocyanate are classified as low (A), low-medium (B), medium (C), medium-high (D), high (E), and very high (F) avidity anti-PT IgG antibodies, respectively. The horizontal line denotes the cord mean levels in newborns born to unvaccinated women. PT, pertussis toxin; IU/ml, international unit/ml. This figure shows that the earlier Tdap is given in pregnancy the higher fractional absolute levels of low-medium, medium, medium–high, and high avidity anti-PT IgG levels are achieved at birth.

Figure 2. Fractional absolute anti-PT IgG levels by time elapsed from vaccination against pertussis in pregnancy to delivery achieved at the different ammonium thiocyanate concentrations. The quantified fractional absolute avidity levels of anti-PT IgG at 0.25 molar (M), 0.5, 1, 1.5, 2, and 3 M of ammonium thiocyanate are classified as low (A), low-medium (B), medium (C), medium-high (D), high (E), and very high (F) avidity anti-PT IgG antibodies, respectively. The horizontal line denotes the cord mean levels in newborns born to unvaccinated women. PT, pertussis toxin; IU/ml, international unit/ml. This figure shows that the longer the interval between Tdap administration during the third trimester and delivery, the higher the fractional absolute levels of low–medium, medium, medium–high, and high avidity anti-PT IgG achieved at birth.

Figure 3. Distribution of total absolute avidity of anti-PT IgG by timing of vaccination in pregnancy (A) and time elapsed between vaccination and delivery (B). Kernel Density plot shows the total absolute avidity of anti-PT IgG in cord sera of newborns of women vaccinated against pertussis in pregnancy at different times. The density curves were obtained using a Gaussian kernel. PT, pertussis toxin; aP, acellular pertussis; WG, weeks gestation; WK, weeks; IU/ml, international unit/ml; AAU/mL, Absolute Avidity Unit/mL. This figure shows that vaccination with Tdap during 28–32 WG resulted in higher total absolute avidity levels of anti-PT IgG compared with newborns born to women vaccinated during 33–36 WG. Vaccination with Tdap 5–12 weeks prior to delivery resulted in higher cord total absolute avidity levels of anti-PT IgG compared with vaccination within 4 weeks prior to delivery.

Figure 4. Heat-map analysis based on hierarchical unsupervised clustering. Fractional absolute levels of anti-PT IgG with different avidities for 112 cord samples are illustrated. In the heat-map, natural log fractional absolute anti-PT IgG levels are shown by column. The natural log fractional absolute anti-PT IgG levels were color-coded as indicated by the scale in the right, in which levels range from blue to red indicating high (red) and low (blue) levels. Timing of tetanus diphtheria and acellular pertussis (Tdap) administration is displayed by the different rows. PT, pertussis toxin; IU/ml, international unit/ml; WG, weeks gestation; M, molar; wks, weeks. This figure shows that most newborns of women vaccinated during 28–32 WG or more than (or equal to) 5 weeks prior to delivery had an avidity profile consisting of high levels of high fractional absolute anti-PT IgG levels.