Using the precaution adoption process model to clarify human papillomavirus vaccine hesitancy in canadian parents of girls and parents of boys

Figures & data

Table 1. Comparison of knowledge, attitudes and beliefs of hesitant (unengaged/undecided versus decided not) parents of girls and parents of boys at Time 1.

	Unengaged and undecided n = 175	Decided not n = 85
	M (SD)	M (SD)	T-test (95% CI) *
Parents of Girls
General HPV Knowledge	12.9 (5.3)	15.1 (4.4)	−3.38; −0.93
HPV Vaccine Knowledge	5.7 (2.6)	7.3 (1.9)	−2.20; −1.08
Susceptibility	4.6 (1.2)	2.7 (1.4)	1.54; 2.24
Severity	5.9 (1.1)	5.3 (1.3)	0.23; 0.89
Benefits	4.6 (0.9)	2.9 (1.0)	1.46; 1.97
Affordability	3.4 (1.4)	2.3 (1.2)	0.72; 1.39
Accessibility	3.0 (1.0)	2.5 (1.2)	0.25; 0.83
Harms	4.3 (1.1)	5.8 (1.0)	−1.81; −1.26
Influence	4.2 (0.8)	3.7 (0.9)	0.29; 0.75
Self-Efficacy	5.8 (1.1)	6.5 (0.8)	−0.98; −0.52
Conspiracy (VCBS)	3.7 (1.5)	5.0 (1.3)	−1.79; −1.09
VHS: Confidence	2.1 (0.7)	2.9 (0.9)	−1.04; −0.60
VHS: Risk	3.4 (0.9)	4.1 (0.7)	−0.90; −0.51
	Unengaged and undecided n = 322	Decided not n = 84
Parents of Boys
General HPV Knowledge	13.2 (5.7)	15.6 (5.1)	−3.67; −1.16
HPV Vaccine Knowledge	5.9 (2.9)	7.1 (2.5)	−1.76; −0.49
Susceptibility	4.6 (1.1)	2.9 (1.3)	1.32; 1.95
Severity	5.8 (1.0)	5.0 (1.5)	0.54; 1.24
Benefits	4.8 (0.9)	3.1 (1.1)	1.46; 1.99
Affordability	4.7 (1.3)	3.8 (1.6)	0.55; 1.32
Accessibility	3.3 (1.1)	3.0 (1.1)	0.09; 0.62
Harms	3.8 (1.2)	5.4 (1.3)	−1.91; −1.27
Influence	3.9 (0.9)	3.2 (1.0)	0.52; 1.00
Self-efficacy	5.7 (1.0)	6.3 (0.9)	−0.83; −0.39
Conspiracy (VCBS)	3.2 (1.4)	4.5 (1.5)	−1.63; −0.91
VHS: Confidence	1.9 (0.6)	2.8 (0.9)	−1.05; −0.61
VHS: Risk	3.2 (0.9)	3.8 (0.9)	−0.83; −0.40

Note: * Welch two sample t-test; CI = confidence interval; M = mean; SD = standard deviation; VCBS = Vaccine Conspiracy and Beliefs Scale; VHS = Vaccine Hesitancy Scale. HPV = human papillomavirus. In bold significant higher means.

Table 2. Changes in PAPM stages of hesitant (unengaged/undecided and decided not) parents of girls and parents of boys from Time 1 to Time 2.

		Unengaged/Undecided Time 1 (n = 175)		Decided not Time 1 (n = 85)
		% (n)		(%) n	Test of proportions^§ 95% CI
Parents of Girls
Time 2 (n = 175)	Unaware*	2.3 (4)	Time 2 (n = 85)	0 (0)	–
	Unengaged	5.7 (10)		1.2 (1)	−0.01; 0.09
	Undecided	38.3 (67)		18.8 (16)	0.08; 0.31
	Decided not	12.0 (21)		70.6 (60)	−0.70; −0.47
	Decided yes	17.7 (31)		7.1 (6)	0.02; 0.07
	Vaccinated	24.0 (42)		2.3 (2)	0.14; 0.30
		Unengaged/Undecided Time 1 (n = 322)		Decided not Time 1 (n = 84)	Test of proportions^§ 95% CI
Parents of Boys
Time 2 (n = 322)	Unaware*	5.3 (17)	Time 2 (n = 84)	2.4 (2)	−0.02; 0.08
	Unengaged	17.1 (55)		8.3 (7)	0.01; 0.17
	Undecided	42.5 (137)		17.9 (15)	0.14; 0.35
	Decided not	5.6 (18)		70.2 (59)	−0.75; −0.54
	Decided yes	19.6 (63)		0 (0)	–
	Vaccinated	9.9 (32)		1.2 (1)	0.04; 0.14

Note: * represents parents’ inaccurate reporting of PAPM stage at Time 2. ^§ represents 2-sample test for equality of proportions with Yates continuity correction. Bold indicates significantly higher proportions. In this table, we present the change in intention stage in parents who responded both at Time 1 and Time 2. Attrition from Time 1 to Time 2 in parents of girls was 187 and 94 for unengaged/undecided and decided not respectively. Attrition from Time 1 to Time 2 in parents of boys was 323 and 68 for unengaged/undecided and decided not respectively.

Table 3. Change of knowledge, attitudes and beliefs in Unengaged/Undecided parents at Time 1 who changed to Decided To or Vaccinated at Time 2.

	Parents of girls			Parents of boys
	Unengaged/Undecided at T1 (n = 175) versus Decided To/Vaccinated at T2 (n = 73)			Unengaged/Undecided at T1 (n = 322) versus Decided To/Vaccinated at T2 (n = 95)
	Mean T1	Mean T2	95% CI	Mean T1	Mean T2	95% CI
General HPV knowledge	12.89	16.21	−4.49; −2.13	13.21	15.77	−3.67; −1.45
HPV Vaccine knowledge	5.70	7.77	−2.62; −1.51	5.94	7.31	−1.96; −0.78
Risk	4.64	5.46	−1.12; −0.52	4.62	5.57	−1.19; −0.71
Severity	5.85	6.07	−0.48; 0.04	5.85	6.10	−0.47; −0.03
Benefits	4.63	5.23	−0.85; −0.34	4.81	5.58	−0.97; −0.57
Affordability	3.39	2.37	0.65; 1.40	4.72	3.64	0.70; 1.45
Accessibility	3.03	2.35	0.41; 0.95	3.32	2.73	0.31; 0.88
Harms	4.30	3.19	0.80; 1.43	3.82	3.03	0.50; 3.03
Cues to action (influence)	4.23	5.24	−1.27; −0.75	3.95	5.11	−1.37; −0.95
Self-efficacy	5.77	6.25	−0.71; −0.24	5.73	6.18	−0.65; −0.26
Conspiracy (VCBS)	3.52	2.99	0.15; 0.90	3.24	2.63	0.30; 0.92
VHS: Confidence	2.08	1.91	−0.01; 0.34	1.96	1.66	0.17; 0.43
VHS: Risk	3.43	2.89	0.31; 0.76	3.20	2.91	0.07; 0.50

Note: In bold significant confidence intervals (CI) for 2 sample Welch t-test. At Time 1 we report the number of parents who also provided responses at Time 2. HPV = human papillomavirus

Table 4. Bivariate logistic regression analysis for boys and girls at Time 2 for decided to/vaccinated versus unengaged/undecided/decided not (reference category).

	Boys (n = 305)	Girls (n = 171)
	OR (CI)	OR (CI)
Knowledge, attitudes and beliefs
General HPV Knowledge	1.03 (0.98; 1.09)	1.14 (1.06; 1.23)
HPV Vaccine knowledge	1.11 (0.99; 1.24)	1.19 (1.03; 1.39)
Susceptibility	2.66 (2.00; 3.54)	2.55 (1.81; 3.58)
Severity	1.36 (1.03; 1.80)	1.22 (0.87; 1.70)
Benefits	2.98 (2.15; 4.13)	2.76 (1.83; 4.15)
Affordability	0.81 (0.69; 0.95)	0.66 (0.53; 0.84)
Accessibility	0.64 (0.51; 0.81)	0.62 (0.46; 0.84)
Harms	0.52 (0.41; 0.64)	0.44 (0.32; 0.59)
Influence	4.41 (3.00; 6.47)	3.79 (2.43; 5.90)
Self-Efficacy	1.77 (1.33; 2.34)	2.30 (1.56; 3.39)
VCBS	0.70 (0.58; 0.84)	0.70 (0.56; 0.87)
VHS: Confidence	0.33 (0.21; 0.52)	0.49 (0.30; 0.81)
VHS: Risk	0.69 (0.52; 0.90)	0.42 (0.28; 0.63)
Vaccine policy change (Ontario, Quebec, Manitoba)
Vaccine policy no change	(reference)	(reference)
change	0.82 (0.49; 1.39)	0.77 (0.41; 1.44)
Sociodemographics
Parents’ age	0.99 (0.96; 1.03)	0.95 (0.91; 1.01)
Age of the child	0.92 (0.83; 1.03)	0.91 (0.79; 1.04)
Education Elementary/high school	(reference)	(reference)
University	1.36 (0.63; 2.92)	1.34 (0.62; 2.87)
Number of children One child	(reference)	(reference)
Two children	1.14 (0.62; 2.10)	1.04 (0.50; 2.20)
Three or more children	1.09 (0.56; 2.12)	1.21 (0.53; 2.80)
Parents’ gender male	(reference)	(reference)
female	1.19 (0.72; 1.96)	0.91 (0.48; 1.70)
Income<100K	(reference)	(reference)
≥100K	1.58 (0.94; 2.65)	0.47 (0.23; 0.93)
Prefer not to answer	1.93 (0.83; 4.49)	0.81 (0.28; 2.34)
Ethnicity Other	(reference)	(reference)
White	0.55 (0.29; 1.05)	0.81 (0.38; 1.76)
HCP recommendation No	(reference)	(reference)
Yes	4.05 (2.07; 7.96)	2.19 (1.07; 4.50)

Note: OR = adjusted odds ratio for decided to/vaccinated versus unengaged/undecided/decided not (reference category). For knowledge, attitudes and beliefs OR is reported for one-unit increase. In bold, significant OR. HPV = human papillomavirus

Table 5. Multivariate logistic regression analysis for boys and girls at Time 2 for decided to/vaccinated versus unengaged/undecided/decided not (reference category).

	Boys (n = 305)	Girls (n = 171)
	AOR (CI)	AOR (CI)
General HPV Knowledge	0.99 (0.91; 1.10)	1.21 (1.05; 1.39)
HPV Vaccine knowledge	1.00 (0.83; 1.19)	1.13 (0.84; 1.53)
Susceptibility	1.46 (0.93; 2.30)	1.39 (0.76; 2.55)
Severity	0.67 (0.43; 1.05)	1.22 (0.68; 2.19)
Benefits	1.14 (0.63; 2.06)	1.11 (0.44; 2.80)
Affordability	0.89 (0.70; 1.13)	0.70 (0.47; 1.03)
Accessibility	1.09 (0.76; 1.56)	1.62 (0.94; 2.78)
Harms	0.63 (0.40; 1.01)	0.47 (0.25; 0.88)
Influence	2.89 (1.77; 4.74)	2.91 (1.50; 5.65)
Self-efficacy	1.29 (0.86; 1.93)	1.48 (0.81; 2.72)
Conspiracy (VCBS)	1.09 (0.73; 1.61)	1.51 (0.86; 2.65)
Hesitancy confidence	0.80 (0.36; 1.77)	2.11 (0.75; 5.91)
Hesitancy risk	1.32 (0.80; 2.24)	0.58 (0.26; 1.29)
Vaccine policy no change	(reference)	(reference)
change	0.96 (0.48; 1.92)	0.83 (0.31; 2.23)
HCP recommendation No	(reference)	(reference)
Yes	2.23 (0.91; 5.46)	1.47 (0.53; 4.08)
Income <100K	(reference)	(reference)
≥100K	1.47 (0.75; 2.90)	0.36 (0.13; 0.99)
Prefer not to answer	1.68 (0.56; 5.05)	0.76 (0.13; 4.35)
Ethnicity Other	(reference)	(reference)
White	0.39 (0.17; 0.90)	0.50 (0.15; 1.68)

Note: HPV = human papillomavirus. AOR: adjusted odds ratio for decided to/vaccinated versus unengaged/undecided/decided not (reference category). For knowledge, attitudes and beliefs AOR is reported for one-unit increase. In bold, significant AOR. Final model fit diagnostics for boys: BIC = 363, goodness of fit (Cessie van Houwelingen) p = 0.95, VIF<3.06, C = 0.87. Model fit diagnostics with all variables from bivariate for boys: BIC = 395, goodness of fit (Cessie van Houwelingen) p = 0.71, VIF<3.30, C = 0.87. Final model fit diagnostics for girls: BIC = 229, goodness of fit (Cessie van Houwelingen) p = 0.64, VIF<3.85, C = 0.90. Model fit diagnostics with all variables from bivariate for girls: BIC = 252, goodness of fit (Cessie van Houwelingen) p = 0.34, VIF<4.47, C = 0.91

Figure 1. Precaution Adoption Process Model (PAPM) vaccination intention stages.

Sociodemographics of hesitant (unengaged/undecided and decided not) parents of girls and parents of boys at Time 1

Parents of Girls
	Unengaged and undecided n=175	Decided not n=85
	n (%)	n (%)	Test of proportions (95% CI) **
Education
Elementary/high school	35 (20.0)	13 (15.3)	-0.05; 0.14
University	140 (80.0)	72 (84.7)	-0.14; 0.05
Number of children
One child	44 (25.2)	17 (20.0)	-0.06; 0.16
Two children	83 (47.4)	44 (51.8)	-0.17; 0.09
Three or more children	48 (27.4)	24 (28.2)	-0.12; 0.11
Parent’s gender
Male	64 (36.6)	23 (27.1)	-0.02; 0.21
Female	111 (63.4)	62 (72.9)	-0.21; 0.02
Income
<100.000	104 (59.4)	42 (49.4)	-0.03; 0.23
≥100.000	55 (31.4)	27 (31.8)	-0.12; 0.12
Prefer not to answer	16 (9.2)	16 (18.8)	-0.19; -0.003
Ethnicity
White	140 (80.0)	73 (85.9)	-0.15; 0.04
Other	35 (20.0)	12 (14.1)	-0.04; 0.15
HCP recommendation-yes	13 (7.4)	18 (21.2)	-0.23; -0.04
HCP recommendation-no	162 (92.6)	67 (78.8)	0.04; 0.23
	M (SD)	M (SD)	T-test (95%CI) *
Parent’s age	42.5 (6.9)	43.3 (6.5)	-1.96; 1.96
Age of the child	11.4 (2.3)	12.4 (2.3)	-1.58; -0.38

Table

Parents of boys
	Unengaged and undecided n=322	Decided not n=84
	n (%)	n (%)	Test of proportions (95% CI) **
Education
Elementary/high school	42 (13.1)	19 (22.6)	-0.19; 0.001
University	280 (86.9)	65 (77.4)	-0.001; 0.19
Number of children
One child	76 (23.6)	21 (25.0)	-0.12; 0.09
Two children	150 (46.6)	29 (34.5)	0.01; 0.24
Three or more children	96 (29.8)	34 (40.5)	-0.22; 0.01
Parent’s gender
Male	128 (39.8)	29 (34.5)	-0.06; 0.17
Female	194 (60.2)	55 (65.5)	-0.17; 0.06
Income
<100.000	168 (52.2)	51 (60.7)	-0.20; 0.03
≥100.000	121 (37.6)	21 (25.0)	0.02; 0.23
Prefer not to answer	33 (10.2)	12 (14.3)	-0.12; 0.04
Ethnicity
White	273 (84.8)	71 (84.5)	-0.08; 0.09
Other	49 (15.2)	13 (15.5)	-0.09; 0.08
HCP recommendation-yes	16 (5.0)	3 (3.6)	-0.03; 0.06
HCP recommendation-no	306 (95.0	81 (96.4)	-0.06; 0.03
	M (SD)	M (SD)	T-test (95%CI)
Parent’s age	44.8 (7.2)	43.3 (7.5)	-0.29; 3.33
Age of the child	13 (2.3)	12.6 (2.4)	-0.21; 0.92

Note: * Welch two sample t-test; ** 2-sample test for equality of proportions; CI = confidence interval; M = mean; SD = standard deviation; VCBS = Vaccine Conspiracy and Beliefs Scale; In bold significant higher means or proportions. HCP= healthcare provider. Included are parents who responded at Time 1 and Time 2

Knowledge, attitudes and behaviors in Decided not and Unengaged/Undecided parents who did not change their vaccination intention stage from Time 1 to Time 2

	Parents of Girls						Parents of Boys
	Decided NOT at Time 1 (n = 85) versus Decided NOT at Time 2 (n = 60)			Unengaged/Undecided at Time 1 (n = 175) versus Unengaged /Undecided at Time 2 (n = 77)			Decided NOT at Time 1 (n = 84) versus Decided NOT at Time 2 (n = 59)			Unengaged/Undecided at Time 1 (n = 322) versus Unengaged OR Undecided at Time 2 (n = 192)
	Mean T1	Mean T2	95% CI	Mean T1	Mean T2	95% CI	Mean T1	Mean T2	95% CI	Mean T1	Mean T2	95% CI
General HPV knowledge	15.05	16.55	-2.91; -0.09	12.89	13.36	-1.80; 0.86	15.62	16.80	-2.65; 0.29	13.21	14.79	-2.51; -0.65
HPV Vaccine knowledge	7.34	7.53	-0.87; 0.49	5.70	6.62	-1.63; -0.21	7.06	7.48	-1.17; 0.34	5.94	6.73	-1.25; -0.34
Risk	2.75	3.12	-0.85; 011	4.64	4.48	-0.15; 0.47	2.98	3.06	-0.53; 0.38	4.62	4.65	-0.21; 0.16
Severity	5.29	5.28	-0.44; 0.43	5.85	5.93	-0.36; 0.21	4.96	4.95	-0.48; 0.50	5.85	5.86	-0.18; 0.16
Benefits	2.92	2.85	-0.28; 0.42	4.63	4.67	-0.25; 0.18	3.09	2.89	-0.19; 0.60	4.81	4.82	-0.16; 0.15
Affordability	2.34	2.53	-0.62; 0.24	3.39	3.33	-0.32; 0.43	3.78	3.05	0.21; 1.25	4.72	4.25	0.20; 0.72
Accessibility	2.49	2.51	-0.42; 0.39	3.03	2.98	-0.26; 0.36	2.96	2.95	-0.36; 0.37	3.32	3.29	-0.15; 0.22
Harms	5.84	6.03	-0.51; 0.14	4.30	4.23	-0.26; 0.40	5.41	5.62	-0.63; 0.20	3.82	3.91	-0.29; 0.12
Cues to action (influence)	3.71	3.73	-0.32; 0.28	4.23	4.17	-0.18; 0.30	3.19	3.28	-0.41; 0.23	3.95	4.01	-0.21; 0.10
Self-efficacy	6.52	6.30	-0.11; 0.55	5.77	5.41	0.06; 0.66	6.34	6.28	-0.29; 0.39	5.73	5.62	-0.08; 0.30
Conspiracy	4.95	5.06	-0.52; 0.30	3.52	3.54	-0.40; 0.35	4.50	4.59	-0.60; 0.43	3.24	3.26	-0.27; 0.23
Hesitancy (confidence)	2.90	2.99	-0.40; 0.20	2.08	2.13	-0.22; 0.12	2.79	2.78	-0.33; 0.34	1.96	2.03	-0.19; 0.04
Hesitancy (risks)	4.13	3.98	-0.11; 0.41	3.42	3.43	-0.24; 0.23	3.81	3.92	-0.39; 0.16	3.20	3.16	-0.13; 0.19

Note: In bold significant confidence intervals (CI) for 2 sample Welch t-test. At Time 1 we report the number of parents who also provided responses at Time 2. HPV = human papillomavirus

Multivariate logistic regression analysis at Time 1 for all parents who received a HCP recommendation related to the HPV vaccine (n=418). Outcome is decided to/vaccinated versus unengaged/undecided/decided NOT (reference category).

	All parents at Time 1
	AOR (95% CI)
General Knowledge	0.93 (0.86; 1.02)
Benefits	1.97 (1.13; 3.42)
Harms	0.45 (0.32; 0.64)
Influence	2.22 (1.35; 3.66)
Strength of HCP recommendation	1.69 (1.21; 2.36)
Childs’ gender male	(reference)
female	5.91 (2.43; 14.40)
Income <100K	(reference)
≥100K	1.86 (0.79; 4.37)
Prefer not to answer	1.39 (0.44; 4.43)
Ethnicity Other	(reference)
White	0.39 (0.14; 1.07)

Note:

HCP = healthcare provider AOR = adjusted odds ratio for decided to/vaccinated versus unengaged/undecided/decided not (reference category). For knowledge, attitudes/beliefs and strength of HCP recommendation AOR is reported for one-unit increase. In bold, significant AOR.

Benefits were measured with a scale of 10 items, the harms scale included 6 items and influence 8 items. General HPV knowledge was measured with 23 items. Benefits (e.g., “The HPV vaccine has many benefits”), harms (e.g., “the HPV vaccine is unsafe”) and influence (e.g., “My family thinks it is a good idea to vaccinate my child against HPV”) were measured on a 7-point Likert scale where 1= strongly disagree and 7= strongly agree. HCP’s strength of recommendation was measured on a 5-point Likert scale where 1= the recommendation does not influence at all the decision to vaccinate their son/daughter and 5 = the recommendation influenced a lot. Model fit diagnostics: BIC=252, goodness of fit (Cessie van Houwelingen) p=0.27, VIF<1.82, C=0.94.

Differences in sociodemographics between parents who participated at Time 2 and those who did not participate at Time 2

	Participated at Time 2 (n=1758)	Did NOT participate at Time 2 (n=1846)
	n (%)	n (%)	Test of proportions (95% CI)	Effect size (Cohen’s h)
Education
Elementary/high school	305 (17.3)	329 (17.8)	-0.03; 0.02	-0.01
University	1453 (82.7)	1517 (82.2)	-0.02; 0.03	0.01
Number of children
One child	411 (23.4)	409 (22.2)	-0.02; 0.04	0.03
Two children	820 (46.6)	849 (46.0)	-0.03; 0.04	0.01
Three or more children	527 (30.0)	588 (31.8)	-0.05; 0.01	-0.04
Parent’s gender
Male	597 (34.0)	627 (34.0)	-0.03; 0.03	-0.0001
Female	1161 (66.0)	1219 (66.0)	-0.03; 0.03	0.0001
Income
<100.000	907 (51.6)	962 (52.1)	-0.04; 0.03	-0.01
≥100.000	674 (38.3)	680 (36.8)	-0.02; 0.05	0.03
Prefer not to answer	177 (10.1)	204 (11.1)	-0.03; 0.01	-0.03
Ethnicity
White	1467 (83.4)	1547 (83.8)	-0.03; 0.02	-0.01
Other	291 (16.6)	299 (16.2)	-0.02; 0.03	0.01
HCP recommendation-yes	216 (12.3)	204 (11.1)	-0.01; -0.03	0.04
HCP recommendation-no	1542 (87.7)	1642 (88.9)	-0.03; 0.01	-0.04
	Mean	Mean	T-test (95%CI)
Parent’s age	44.08	42.98	0.64; 1.54	0.16
Age of the child	12.62	12.54	-0.07; 0.23	0.03

Note: In bold significant higher proportions or means. Effect size values <0.2 are considered small and the difference between proportions or means trivial even if statistically significant (two-sample test of proportions or Welch two sample t-test).

Differences in knowledge, attitudes and beliefs between parents who participated at Time 2 and those who did not participate at Time 2

	Participated at Time 2 (n=1758)	Did NOT participate at Time 2 (n=1846)
	Mean	Mean	T-test (95% CI)	Effect size (Cohen’s d)
General HPV Knowledge	13.34	12.51	0.44; 1.22	0.14
HPV Vaccine Knowledge	6.30	5.84	0.27; 0.65	0.16
Susceptibility	5.01	4.90	0.01; 0.20	0.08
Severity	5.95	5.93	-0.055; 0.09	0.02
Benefits	4.97	4.88	0.01; 0.16	0.08
Affordability	3.57	3.60	-0.14; 0.08	-0.02
Accessibility	2.77	2.86	-0.16; -0.01	-0.08
Harms	3.49	3.53	-0.14; 0.05	-0.03
Influence	4.69	4.59	0.02; 0.17	0.08
Self-Efficacy	6.07	6.00	0.01; 0.14	0.08
VCBS	3.14	3.25	-0.20; -0.01	-0.07
VHS: Confidence	1.93	2.01	-0.12; -0.03	-0.10
VHS: Risk	3.05	3.06	-0.07; 0.05	-0.01

Note: In bold significant higher means. Effect size values <0.2 are considered small and the difference between means trivial even if statistically significant (Welch two sample T-test).