Table 2.

Cortisol reactivity to vaccination

Birth group	Cortisol reactivity to vaccine Mean±SD	Estimated group differences in cortisol reactivity (95% CI)	P value
Birth group comparisons
Term (≥37 weeks), n=45	13.1±11.9	Reference
Preterm (≤32 weeks), n=56	9.3±10.2	−3.9 (−8.3 to 0.5)	0.09
Extremely preterm (<28 weeks), n=14	5.8±8.5	−7.3 (−14.0 to −0.6)	0.03
Very preterm (28–32 weeks), n=42	10.4±10.6	−2.7 (−7.4 to 2.0)	0.26
Birth group comparisons stratified by sex
Male term (≥37 weeks), n=21	14.5±11.7	Reference
Male preterm (≤32 weeks), n=38	6.8±8.7	−7.7 (−13.4 to −2.0)	0.009
Female term (≥37 weeks), n=24	11.9±12.2	Reference
Female preterm (≤32 weeks), n=18	14.5±11.5	2.5 (−4.5 to 9.6)	0.47

Cortisol reactivity was calculated by subtracting the prevaccine cortisol concentration from the postvaccine cortisol concentration.

Effect sizes represent cortisol concentrations in nmol/L.