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Table 2 Mean diphtheria, tetanus and pertussis antibody titres in infants at 12 and 24 weeks of age by season of mid-gestation and first DTP vaccination

From: Seasonal modulation of antibody response to diphtheria-tetanus-pertussis vaccination in infants: a cohort study in rural Gambia

  Season of mid-gestation Season of vaccination
Vaccine Dry/Harvest season (n = 335) Rainy/Hungry season (n = 375) Effect size (95%CI)a p-valueb Dry/Harvest season (n = 486) Rainy/Hungry season (n = 224) Effect size (95%CI)a p-valueb
12 weeks
 Diphtheria 0.23 (0.20, 0.26) 0.07 (0.07, 0.08) 50.8 (45.2, 56.4) < 0.001 0.08 (0.08, 0.09) 0.35 (0.31, 0.39) −62.3 (−67.2, −57.4) < 0.001
 Tetanus 0.75 (0.71, 0.78) 0.54 (0.52, 0.55) 14.4 (12.0, 16.7) < 0.001 0.55 (0.54, 0.57) 0.81 (0.78, 0.85) − 16.9 (− 19.2, − 14.6) < 0.001
 Pertussis 6.1 (5.8, 6.5) 4.1 (4.0, 4.3) 17.2 (14.5, 19.9) < 0.001 4.4 (4.3, 4.6) 7.0 (6.6, 7.4) −19.7 (−22.6, − 16.7) < 0.001
24 weeks
 Diphtheria 1.1 (1.1, 1.2) 1.7 (1.6, 1.7) −15.8 (− 17.8, − 13.8) < 0.001 1.6 (1.6, 1.7) 1.0 (0.98, 1.1) 20.6 (18.9, 22.3) < 0.001
 Tetanus 3.5 (3.5, 3.6) 3.5 (3.4, 3.6) 0.30 (−1.3, 1.9) 0.734 3.5 (3.5, 3.6) 3.4 (3.3, 3.6) 1.3 (−0.80, 3.3) 0.230
 Pertussis 103.1 (95.7, 111.1) 74.5 (69.1, 80.3) 14.1 (9.5, 18.7) < 0.001 87.7 (82.7, 93) 94.8 (87.1, 103.3) −3.4 (−7.9, 1.1) 0.142
  1. Note: Mean antibody titres measured at 12 weeks, following the first DTP vaccination, were adjusted with maternal variables: age, BMI and formal education (yes/no) at enrolment, Hb levels at 30 weeks gestation, weight gain from enrolment to 30 weeks gestation, morbidity, supplement group and compliance to supplementation from enrolment to delivery; and with infant variables: GA at delivery, sex, WLZ at first vaccination, Hb levels at 12 weeks, morbidity, EBF (yes/no), and Fourier terms of month of mid-gestation or first vaccination. Mean antibody titres measured at 24 weeks, following the third DTP vaccination, were adjusted with the same factors mentioned above, with changes for infant WLZ at third vaccination, Hb levels at 24 weeks and morbidity and EBF (yes/no) from birth to 24 weeks. Abbreviations: BMI, body mass index; CI, confidence interval; DTP, diphtheria-tetanus-pertussis; EBF, exclusively breastfed; GA, gestational age; Hb, haemoglobin; WLZ, weight-for-length-z-score
  2. aEffect sizes were determined using the mean difference between the dry/harvest season and rainy/hungry season of vaccination from the Student’s t-test and were expressed as percentages (%)
  3. bThe p-values were calculated by Student’s t-test on the log-transformed antibody concentrations