Table 5

Multivariable analysis of influence of gestational age, birth weight, pre-immunisation IgG levels, age at completion of immunisations, and use of antenatal and postnatal steroids on IgG response of preterm infants to vaccine antigens

Percentage change in IgG titre per unit change in variable p value
Gestational age (weeks)Birth weight (100 g)Pre-immunisation IgG level (IU/ml)Age at completion (weeks)Antenatal steroids (number of doses)Postnatal steroids (number of courses)
Values in parentheses are 95% confidence intervals.
*Example: 2.2% increase in diphtheria IgG for each week of gestational age at birth.
FHA, filamentous haemagglutinin; PRN, pertactin; PT, pertussis toxin.
Diphtheria+2.2*+0.7−4.5+1.1−1.8+4.8
(−2.5 to +7.0)(−1.8 to +3.1)(−16.0 to +7.0)(−1.7 to +4.0)(−8.3 to +4.8)(−11.2 to +20.8)
p = 0.36p = 0.58p = 0.44p = 0.42p = 0.59p = 0.55
Tetanus+7.1−2.8−18.3+5.3−9.2−2.6
(+1.5 to +12.7)(−5.6 to +0.04)(−31.6 to −5.0)(+2.2 to +12.2)(−16.8 to −1.7)(−21.2 to +16.0)
p = 0.014p = 0.053p = 0.007p = 0.001p = 0.017p = 0.79
FHA+5.9−2.0−17.0+2.2−5.7+10.6
(+0.9 to +10.9)(−4.5 to +0.49)(−32.8 to −1.2)(−0.7 to +5.0)(−12.6 to +1.1)(−4.2 to +25.5)
p = 0.02p = 0.12p = 0.035p = 0.14p = 0.097p = 0.16
PRN+7.4−0.7−36.4+5.6−3.0−4.1
(+1.5 to +13.3)(−3.7 to +2.2)(−51.7 to −21.1)(+2.1 to +9.1)(−11.3 to +5.3)(−22.0 to +13.8)
p = 0.015p = 0.62p<0.001p = 0.002p = 0.476p = 0.65
PT+10.6−3.4−11.3+0.9−6.8+11.2
(+5.2 to 15.9)(−5.9 to −0.9)(−25.5 to +3.0)(−2.1 to +3.9)(−14.0 to +0.3)(−4.2 to +26.6)
p<0.001p = 0.008p = 0.12p = 0.56p = 0.061p = 0.15