Online study of health professionals about their vaccination attitudes and behavior in the COVID-19 era: addressing participation bias

Figures & data

Table 1. Number of respondents to the survey per phase, French general practitioners, unweighted data, October to November 2020

Phase	N	%
No reminder^a (<09/10/2020)	256	21.17
1 to 2 reminders (09 to 18/10/2020)	411	34.00
3 to 5 reminders (19 to 25/10/2020)	184	15.22
Telephone interviews^b (>25/10/2020)	358	29.61
Total	1,209	100.00

^aReminders were made by sending an e-mail or a text message to the panel members who had not yet responded

^bGPs who had not completed the questionnaire online were contacted by trained professional interviewers (Kantar Public) to invite them to complete the questionnaire with them on the phone. During this phase, 74 GPs preferred completing the questionnaire online: these GPs have been put in the last category because, along with those who were interviewed by telephone, they were the last to participate.

Table 2. Trends in respondents’ demographic and professional characteristics throughout the survey, French general practitioners, unweighted data, October to November 2020

	Survey phases of the survey
	No reminder	1–2 reminders	3–5 reminders	Telephone reminder &/or interview		Total
	N = 256	N = 411	N = 184	N = 358	p-value^a	N = 1,209
	Col. uW%	Col. uW%	Col. uW%	Col. uW%		uW%^b	W%^c
Gender
Male	49.22	43.07	52.72	64.80	< 0.001	52.27	60.87
Female	50.78	56.93	47.28	35.20		47.73	39.13
Age (years)
<50	51.95	52.80	40.22	36.31	< 0.001	45.82	31.18
50–59	28.13	22.38	26.63	26.82		25.56	32.24
60+	19.92	24.82	33.15	36.87		28.62	36.57
Region
National	63.28	58.64	66.30	62.29	0.20	61.87	85.68
Southeast	17.58	18.73	14.13	21.23		18.53	8.66
West	19.14	22.63	19.57	16.48		19.60	5.66
Workload
Min-Q1	30.47	33.09	25.00	23.74	0.003	28.54	23.33
Q1-Q3	55.47	52.31	54.35	52.23		53.27	50.79
Q3-Max	14.06	14.60	20.65	24.02		18.20	25.88
GPs density of practice area (deciles)
Decile 1	10.94	12.90	13.04	16.76	0.19	13.65	6.55
Deciles 2 to 10	89.06	87.10	86.96	83.24		86.35	93.45
Occasional practice of complementary and alternative medicine (CAM)
Yes	10.16	15.57	17.93	11.73	0.048	13.65	15.75
No/Don’t know	89.84	84.43	82.07	88.27		86.35	84.25

^ap-value: Chi-squared test

^buW: unweighted

^cW: weighted

Table 3. Trends of respondents’ opinions and attitudes throughout the survey, French general practitioners, unweighted data, October to November 2020

	Phases of the survey
	No reminder	1–2 reminders	3–5 reminders	Telephone reminder &/or interview		Total
	N = 256	N = 411	N = 184	N = 358	p-value^a	N = 1,209
	Col. %	Col. %	Col. %	Col. %		uW%^b	W%^c
Covid-19 vaccine acceptance
High acceptance	47.27	45.26	42.93	48.32	0.17	46.24	50.59
Moderate acceptance	23.83	27.01	27.72	30.73		27.54	24.39
Hesitancy or reluctance	28.91	27.74	29.35	20.95		26.22	25.02
I trust the ministry of health to ensure that vaccines are safe
Disagree/Don’t know^d	31.64	28.22	20.65	18.16	< 0.001	24.81	24.10
Agree	68.36	71.78	79.35	81.84		75.19	75.90
Were you vaccinated against seasonal influenza for the winter 2019–2020 season?
No/Don’t know^d	11.72	11.19	11.96	14.80	0.46	12.49	14.70
Yes	88.28	88.81	88.04	85.20		87.51	85.30
The safety of a vaccine developed in an emergency, during an epidemic, cannot be considered guaranteed
Disagree	44.53	38.44	37.50	46.37	0.07	41.94	42.45
Agree/Don’t know^d	55.47	61.56	62.50	53.63		58.06	57.55
In your opinion, for the population as a whole, how serious is COVID-19 on a scale of 0 to 10?
Moderate/High/Don’t know^d [5–10]	67.19	69.34	76.09	79.61	0.001	72.95	72.54
Low [0–4]	32.81	30.66	23.91	20.39		27.05	27.46

^ap-value: Chi-squared test

^buW: unweighted

^cW: weighted

^dDue to their small sizes, “don’t know” categories were merged with others.

Table 4. Factors associated with Covid-19 vaccines acceptance among French GPs, polytomous probit regressions with sample selection (on all GPs eligible for the panel, N = 11,146), unweighted data, October to November 2020

			Covid-19 vaccine
			acceptance (ref. High^a)
	Participation in the study^b (ref. No)		Moderate		Hesitancy/reluctance
	N = 11,146		N = 1,209		N = 1,209
	Coef^c	[CI 95%]^d	Coef	[CI 95%]	Coef	[CI 95%]
Characteristics
Gender (ref. Male)
Female	0.11**	[0.04,0.18]	0.18	[−0.07,0.44]	0.48**	[0.16,0.80]
Age (ref. < 50)
50 to 60	−0.31***	[−0.39,-0.24]	−0.39*	[−0.71,-0.08]	−0.16	[−0.56,0.24]
> 60	−0.38***	[−0.46,-0.30]	−0.54**	[−0.86,-0.21]	−0.24	[−0.68,0.21]
Region (ref. National)
Southeast	−0.19***	[−0.27,-0.10]	0.05	[−0.25,0.34]	0.38*	[0.06,0.70]
West	−0.10*	[−0.19,-0.02]	−0.07	[−0.35,0.20]	−0.19	[−0.53,0.15]
Low density practice area (ref. No)
Yes	−0.11**	[−0.19,-0.03]
Workload (ref. Low [Q1])
Moderate [Q2-Q3]	−0.04	[−0.12,0.03]	−0.17	[−0.42,0.07]	−0.25	[−0.54,0.03]
High [Q4]	−0.19***	[−0.28,-0.09]	−0.54**	[−0.87,-0.22]	−0.24	[−0.63,0.16]
Occasional practice of complementary and alternative medicine (CAM) (ref. No/Don’t know)
Yes			0.36*	[0.04,0.68]	0.22	[−0.14,0.59]
Perceived risks of new vaccines in emergencies and of Covid-19
The safety of a vaccine developed in an emergency, during an epidemic, cannot be considered guaranteed (ref. Disagree)
Agree			0.97***	[0.67,1.28]	1.93***	[1.54,2.31]
Don’t know			0.56**	[0.21,0.91]	1.31***	[0.87,1.76]
Perceived risks of Covid 19
In your opinion, for the population as a whole, how serious is COVID-19 on a scale of 0 to 10?
Low [0–4]			0.26*	[0.03,0.50]	0.47***	[0.20,0.74]
Trust in science and in the ministry of health
I trust the ministry of health to ensure that vaccines are safe (ref. Disagree)
Agree			−0.31	[−0.64,0.01]	−0.86***	[−1.22,-0.50]
Don’t know/no response			−0.11	[−0.61,0.38]	0.10	[−0.40,0.61]
Personal vaccination
Were you vaccinated against seasonal influenza for the winter 2019–2020 season? (ref. No/non-response)
Yes			−0.43*	[−0.79,-0.07]	−0.87***	[−1.26,-0.48]

P-values: *: <0.05; **: <0.01; ***: <0.001; ^aBecause the dependent variable (i.e. acceptance) has three categories ((i) ‘high acceptance’, (ii) ‘moderate acceptance’ and (iii) ‘hesitancy/reluctance’), there are two comparisons (multiple polytomous probit regression): ‘moderate acceptance’ is compared to ‘high acceptance’ (reference), and ‘hesitancy/reluctance’ is also compared to ‘high acceptance’. Positive probit coefficient indicate a positive association with the dependent variable (e.g. female were more likely to participate in the study) whereas negative coefficients indicate a negative association (e.g. older GPs were less likely to participate in the study). The higher the absolute value of the probit coefficient, the greater the strength of the association.

^bFactors associated with participation to the study; these would have been used to correct the estimates of the next two columns, in the presence of selection bias; in the present analysis however, we did not find evidence for such bias.

^cProbit coefficient; ^d Confidence Interval; p-value LR test: 0.62 (comparison between models with and without sample selection; this non-significant result indicates there is no evidence for selection bias); rho_moderate = 0.49 (correlation between study participation and moderate acceptance); rho_hesitancy = −0.15 (correlation between study participation and hesitancy)