Table 3

Initiation of HPV vaccination and RDs according to parental education by income level, N=84 139

	Income below median value*				Income above median value*
	Initiated HPV vaccination		Multivariable model†		Initiated HPV vaccination		Multivariable model†
	n	%	RD	95% CI	n	%	RD	95% CI
Maternal education (years of schooling)
Compulsory (≤10)	9169	77.9	0	Ref	2431	80.1	0	Ref
Upper secondary, levels 1 and 2 (11–12)	3557	77.0	−1.3	−2.8 to 0.2	1 617	78.8	−0.9	−3.3 to 1.5
Upper secondary, completed (13–14)	12 452	78.0	−1.3	−2.4 to −0.2	8676	80.4	−0.5	−2.2 to 1.2
Higher, undergraduate level (14–17)	6463	73.2	−5.6	−6.9 to −4.3	16 444	80.1	−0.6	−2.2 to 1.1
Higher, graduate level (≥18)	588	65.7	−11.4	−14.7 to −8.0	4446	78.5	−1.0	−2.9 to 0.9
				p<0.0001				p=0.88
Paternal education (years of schooling)
Compulsory (≤10)	9257	78.6	0	Ref	3117	79.2	0	Ref
Upper secondary, levels 1 and 2 (11–12)	3170	77.5	−0.5	−2.0 to 1.1	1670	78.0	−0.4	−2.7 to 1.8
Upper secondary, completed (13–14)	14 140	78.7	−0.2	−1.3 to 0.8	13 230	79.7	0.5	−1.0 to 1.9
Higher, undergraduate level (14–17)	5103	75.4	−3.1	−4.5 to −1.8	9111	77.7	−0.9	−2.4 to 0.7
Higher, graduate level (≥18)	1049	72.1	−5.4	−8.0 to −2.9	5996	78.1	0.7	−0.9 to 2.4
				p<0.0001				p=0.054

*Median maternal income=NOK 396 149. Median paternal income=NOK 525 861. NOK=Norwegian kroner (€1 EUR≈8.5 NOK).
†The maternal model included maternal income (categorised as below or above median income), education and employment status, country of origin, urbanity, maternal age at birth of daughter, number of siblings, county of residence, year of birth, and interaction terms between maternal education and income. The paternal model included paternal income (categorised as below or above median income), education and employment status, country of origin, urbanity, maternal age at birth of daughter, number of siblings, county of residence, year of birth, and interaction terms between paternal education and income.
HPV, human papillomavirus; RD, risk difference.