Preference and willingness to pay of female college students for human papillomavirus vaccination in Zhejiang Province, China: A discrete choice experiment

ABSTRACT

The study aimed to quantify the preferences of female college students for human papillomavirus (HPV) vaccination in Zhejiang Province, China, using a discrete choice experiment (DCE). One medical college and one nonmedical college were selected using convenience sampling, and the respondents were identified using stratified cluster sampling. A DCE focused on vaccine-related and service-related attributes was conducted in 2019. Latent class analysis was used to estimate the vaccine-related attributes, and conditional logistic regression was used to construct the choice model for the service-related attributes. In total, 850 female college students finished the study. Two latent classes were identified. Those who had more knowledge of HPV and felt more pressure about the related infection and diseases had a significantly higher chance of belonging to class 1 and were more likely to choose vaccination (percentages of respondents choosing no vaccination was 1.1% in class 1 versus 84.7% in class 2, χ² = 641.1, P < .01). There were 742 respondents who chose vaccination in vaccine-related scenes, and 98.8% of them still chose to receive the vaccine in service-related scenes. Ways of making an appointment, number of weeks waiting for vaccination, service time for vaccination, time to the nearest vaccination site, and added cost all impacted the probability of choosing HPV vaccination services. It is concluded that higher levels of HPV knowledge and sociopsychological pressure led to a higher probability of HPV vaccination uptake in China. It is necessary to disseminate proper knowledge of HPV to improve the coverage and equality of HPV vaccination.

KEYWORDS:

• Preference
• willingness to pay
• human papillomavirus vaccination
• discrete choice experiment
• China

Introduction

Cervical cancer is one of the most common cancer types in women worldwide, and can be effectively prevented through human papillomavirus (HPV) vaccination and cervical cancer screening.^1,2 Persistent infection of high-risk HPV types may progress to cervical intraepithelial neoplasia (CIN) and to cervical cancer within months or years. Large prelicensure trials have illustrated that HPV vaccines have high efficacy (extent of protection under carefully controlled scientific testing conditions) against persistent infection of vaccine-containing HPV types and associated CIN grade 2 or worse (CIN2+) in women without infection at vaccination.³ According to the number of HPV types that the vaccines protect against, there are bivalent, quadrivalent and nonavalent HPV vaccines. The bivalent HPV vaccine contains purified viral L1 protein for HPV types 16 and 18 and protects against persistent infection, CIN and cervical cancer caused by the two HPV types (consisting of approximately 70% of all cervical cancers caused by HPV infections). The quadrivalent HPV vaccine contains purified viral L1 protein for HPV types 6, 11, 16, and 18. It offers similar protection against HPV types 16 and 18 as the bivalent HPV vaccine and protects against anogenital warts causally related to HPV types 6 and 11. Compared to the quadrivalent HPV vaccine, the nonavalent HPV vaccine contains 5 additional purified viral L1 proteins for HPV types (31, 33, 45, 52, and 58) and protects against approximately 90% of HPV-caused cervical cancers and against anogenital warts causally related to HPV types 6 and 11.

The World Health Organization (WHO) recommended that HPV vaccines should be included in national immunization programs (NIPs).⁴ More than 60 countries have nationally implemented HPV immunization programs since 2006.⁵ In 2018, it was estimated that China had approximately 106,430 new cervical cancer cases diagnosed annually, accounting for nearly one-fifth of all new cases in the world.⁶ However, China’s national regulatory authority (NRA) did not approve the first HPV vaccine (bivalent HPV vaccine, CERVARIX) until 2016. In the following four years, the quadrivalent HPV vaccine (GARDASIL®), nonavalent HPV vaccine (GARDASIL 9), and a domestic bivalent HPV vaccine (Cecolin) were approved. There are challenges for China to reach high coverage of HPV vaccines. None of the HPV vaccines are included in the NIP, which means that there are no national recommendations, coverage goals, or financial guarantees for HPV vaccination. HPV vaccines are received voluntarily among the 9 to 45 year-old female population. However, the relatively high vaccination costs (approximately 145-580 USD for all 3 doses depending on different HPV vaccine types) and limited supplies make it difficult to reach out to women from all socioeconomic classes, especially those from rural areas or low socioeconomic class.⁷ In addition, a large amount of information from online news and social media platforms has led to scarcity perceptions, and women exposed to the information have uneven vaccination intentions for different HPV types (with the scarcer vaccine being perceived as better).⁸

Studies have shown that knowledge of HPV,^9,10 personal characteristics (attitudes, beliefs, subjective norms, habits, etc.),¹¹ perceived vaccine attributes (efficacy, safety, etc.),^12,13 service delivery factors (accessibility, convenience, etc.),^14,15 costs and financial incentives¹⁶ may influence the willingness to accept HPV vaccine. A few studies used formal quantitative techniques such as discrete choice experiments (DCEs) to quantify the preferences for HPV vaccination but mainly focused on vaccine-related attributes.^17–19 Thus far, studies in China have mainly focused on the intention to take the vaccine and potential factors, such as HPV knowledge and personal and socioeconomic characteristics.^20–22 It has not been clarified how different vaccine-related attributes and service-related attributes (convenience of making an appointment, geographical accessibility of the vaccination service, etc.) influence the preferences for HPV vaccination in the Chinese population and their willingness to pay (WTP) for different vaccination service-related attributes. If the preferences and influential attributes are determined, measures can be taken to improve coverage by optimizing the attributes.

Female college students were chosen as the study population for the following two reasons. First, they are important targets for HPV vaccination in China. High efficacy of HPV vaccines is observed in women who have not been infected with HPV (HPV-naive), but the evidence is conflicting in women who had evidence of prior HPV exposure.⁴ Considering that HPV is mainly sexually transmitted, it is better to receive HPV vaccination before first sexual intercourse. A study of 18,000 Chinese college students in 2015 showed that more than three-quarters of them had not had sexual intercourse,²³ which means that they can obtain the best protection from HPV vaccination. Furthermore, they may choose from all the types of HPV vaccines available in China, because the bivalent, quadrivalent, and nonavalent HPV vaccines are approved to be used among 9 to 45 year-old, 20 to 45 year-old, and 16 to 26 year-old female populations respectively, in China.

The study aims to quantify the preferences of female college students for HPV vaccination in Zhejiang Province, a developed province located in Southeast China, using a DCE. This research focuses on vaccine-related and service-related attributes. It tries to determine how personal characteristics affect the preference for HPV vaccines with different vaccine-related attributes and predicts the demand for the four types HPV vaccines in the market. This study also explores the WTP for different service-related attributes of HPV vaccination.

Materials and methods

Study population

One medical college and one nonmedical college were selected in Zhejiang Province using convenience sampling. The respondents were identified using stratified cluster sampling to reduce the potential errors associated with sampling. In each undergraduate grade, classes were randomly sampled. The female students in the sampled classes were encouraged to participate in the study by college counselors and would receive a small gift after finishing the survey. Additional classes were sampled to guarantee that at least seventy-two female students were included. There were five grades in medical colleges and four grades in nonmedical colleges.

Discrete choice experiment

A DCE is an attribute-based approach to collect preference data. It presents respondents with a sequence of hypothetical scenarios (choice sets) composed of two or more competing alternatives that vary along with several attributes; one of them may be the price of the alternatives or some approximation for it. For each choice set, respondents are asked to choose their preferred alternative. Responses enable the analyst to model the probability of an alternative being chosen as a function of the attributes and the respondents’ socioeconomic characteristics.²⁴ DCEs have been widely used in health care (including vaccination) evaluations.^24–26 Through model construction, the relative weights of different vaccination features (effectiveness, side effect rate, doses, target age, costs, etc.) can be estimated,^27,28 and the predicted probability that a target subject chooses to take the vaccine can be calculated.^27–29

Survey

In the DCE design, two groups of attributes were considered: vaccine-related and service-related attributes. Vaccine-related attributes focused on vaccine properties, such as the degree and duration of protection and side effect rates. Service-related attributes focused on service aspects including the way of making an appointment, service time, time to the nearest vaccination site, etc. A literature study and an online survey were conducted to select realistic and relevant attributes. Attribute levels were identified based on the literature and the actual conditions in China. The final attributes and levels are shown in Table 1. There were five attributes in both groups, and they gave rise to 144 and 384 possible choice options, respectively. Orthogonal main effects plans were used to select 16 choice options in both groups. The attribute levels of each choice option were changed systematically (added by one level) to create the second option and an opt-out option was added. Thus, there were three choice options in each choice set and a total of 16 choice sets in each group. Each respondent was first randomly allocated to a vaccine-related choice set. If she chose a specific vaccine rather than the opt-out option, then a service-related choice set would be randomly allocated to her. Otherwise, if she chose the opt-out option in the vaccine-related choice set, the service-related choice set would not be allocated. For examples of choice sets, please see Figure 1.

Table 1. Attributes and levels

Attributes	Levels
Vaccine-related
Degree of protection	71% against cervical cancer
	71% against cervical cancer and 90% against genital warts
	90% against cervical cancer and 90% against genital warts
Duration of protection (years)	15, 30, 45
Risk of serious side effects	low level(1:100000), high level(1:10000)
Risk of mild side effects	low level (1:100), high level (1:10)
Cost (CNY)	1000, 2000, 4000, 8000
Service-related
Ways of making an appointment	on site, by phone, by the Internet, through school
Number of weeks waiting for vaccination	1, 4, 12, 24
Service time for vaccination	weekdays only, weekdays and weekends
Time to the nearest vaccination site	<30 minutes, 30–60 minutes, ≥60 minutes
Added cost (CNY)	0, 100, 200, 300

CNY indicates Chinese Yuan, and 1 CNY = 0.145 USD in 2019.

Figure 1. Examples of choice sets

In addition to the DCE choice sets, information on grade, education level of parents, living expenditure per month, source of monthly living expenditure, sexual experience, knowledge of HPV, and sociopsychological pressure of the respondents was collected. Knowledge of HPV was determined through 9 questions: outcome of infection, relationship between infection and diseases, population at risk, routes of transmission, optimal time to get vaccinated, number of vaccination doses, necessity of cervical cancer screening after vaccination, methods of cervical cancer screening and methods of HPV prevention. The scores ranged from 0 to 9, with higher scores referring to higher knowledge. Sociopsychological pressure about HPV-related infection and diseases was determined through 13 questions: 12 questions were scored to measure anxiety, depression, or anger, and each ranged from 1 to 11; the last question was scored to measure positive attitudes toward future health and ranged from 1 to 11. Thus, the total scores were calculated by summing the 12 negative questions and subtracting the positive question, ranging from 1 to 131. Higher scores were referred to higher pressure. Information about whether they had been vaccinated or made an appointment for the HPV vaccine was also collected. The survey was conducted in September 2019 using a Chinese online survey system named Wen Juan Xing. Almost all female students in the sampled classes participated in the study. All the respondents finished the survey, and the average completion time was 6.5 minutes.

Data analysis

The choice observations resulting from the DCE were used to estimate the impacts of vaccine-related and service-related attributes on the probability of an alternative being chosen. A significant independent variable in the choice model indicates that the attribute or attribute level has a significant impact on vaccination behavior, and the sign of the coefficient reflects whether this impact is positive or negative.

The vaccine-related and service-related attributes were grouped in different choice sets and thus were analyzed separately. Latent class analysis was used to estimate the vaccine-related attributes considering 12.7% of the respondents choosing the opt-out option. Latent class analysis assumes that there are two or more classes of people underlying the data with similar choice preferences and uses the Bayesian information criterion (BIC) to choose the optimal number of latent classes. Age, education level of parents, living expenditure per month, source of monthly living expenditure, sexual experience, score of HPV knowledge and score of sociopsychological pressure were used to characterize the class membership model. A choice model indicating the impacts of different attributes and the probability for the specific choice made by class members was estimated for each class. The predicted uptake of a specific vaccine in one class was calculated by taking the exponent of utility for this type of vaccine divided by the exponent of the total utility for all vaccines. (Predicted uptake of vaccine i = ${\mathrm{e}}^{V_i}/\sum _{j=1}^n{\mathrm{e}}^{V_j}$, $V_i$ indicates the utility of vaccine i calculated by the choice model, and n indicates the total number of vaccine types.)

For service-related attributes, 742 respondents participated in the service-related choice set, and 98.8% of them chose to receive the vaccination. Conditional logistic regression was used to construct the choice model, and the nine respondents who chose not to receive the vaccination were excluded to improve the analysis efficiency. Marginal WTP was estimated by dividing the coefficient of another attribute by the negative coefficient of cost. (Marginal WTP = -${\beta }_i/{\beta }_{cost}$)

SPSS 20.0 was used to select subsets of choice options based on orthogonal main effects plans and Stata 13.0 was used for other analyses, such as latent class analysis (the lclogit command) and conditional logistic regression (the clogit command).

Ethical compliance

The study was approved by the Medical Ethics Committee of Zhejiang Provincial Center for Disease Control and Prevention.

Results

In total, 850 female college students participated in and finished the study. (Please see Table 2.) Among them, 45.3% were from the medical college. Most students (66.5%) had living expenditures of 1000–2000 Chinese yuan (CNY, approximately 145-290 USD) per month, and 8.7% had living expenditures of below 1000 CNY (approximately 145 USD) per month. More than 90% of the students received the money mainly from their families. Only 15.2% of them ever had a sex life.

Table 2. Characteristics of respondents

Characteristics	Description
Age median (interquartile range)	20 (19–21)
Average score of HPV knowledge * (standard error)	4.30 (0.08)
Average score of sociopsychological pressure ^† (standard error)	72.47 (1.01)
	N	%
Grade
First	220	25.9
Second	215	25.3
Third	169	19.9
Fourth	174	20.5
Fifth	72	8.5
Medical college
No	465	54.7
Yes	385	45.3
Parents’ education level
Below high school	349	41.1
High school and above	501	58.9
Living expenditure per month (CNY)
<1000	74	8.7
1000–2000	565	66.5
≥2000	211	24.8
Source of monthly living expenditure
Mainly from family	783	92.1
50% from family	38	4.5
Mainly from themselves	29	3.4
Ever had a sex life
No	721	84.8
Yes	129	15.2

CNY indicates Chinese Yuan, and 1 CNY = 0.145 USD in 2019.

* The scores of HPV knowledge range from 0 to 9, and a higher score refers to higher knowledge.

† The sociopsychological pressure scores range from 1 to 131, and a higher score indicates higher pressure.

Two latent classes were identified. Those who had more knowledge of HPV and felt more pressure about the related infection and diseases had a significantly higher chance of belonging to class 1. Respondents belonging to class 1 (86.1% of the respondents) preferred a vaccine with a higher degree and longer duration of protection and a lower risk of serious side effects and cost. However, respondents belonging to class 2 (13.9% of the respondents) seemed to care nothing about the vaccine-related attributes (for more details, please see Table 3). In fact, respondents in class 2 were more likely to choose no vaccination (1.1% in class 1 versus 84.7% in class 2, χ² = 641.1, P < .01). The real vaccination behaviors of the respondents were analyzed, and 138 of them had been vaccinated or made an appointment. Among them, 131 respondents belonged to class 1 and 7 respondents belonged to class 2. (χ² = 10.696, P = .001)

Table 3. Regression coefficients of vaccine-related attributes and class membership model for two latent classes based on responses to a survey investigating preferences for human papillomavirus (HPV) vaccination among female college students in Zhejiang Province, China (n = 850)^*

	Coefficient	SE	z	P > z	95% CI
Class 1
Degree of protection
None (ref)
71% against cervical cancer	2.09	0.76	2.76	0.006	0.60	3.58
71% against cervical cancer and 90% against genital warts	2.99	0.75	4.01	0.000	1.53	4.45
90% against cervical cancer and 90% against genital warts	4.17	0.81	5.12	0.000	2.57	5.76
Duration of protection (per year)	0.04	0.01	5.17	0.000	0.02	0.05
Risk of serious side effects (per higher level of risk)	−0.25	0.12	−2.17	0.030	−0.48	−0.02
Risk of mild side effects (per higher level of risk)	−0.18	0.12	−1.59	0.112	−0.41	0.04
Cost (per 1000 CNY)	−0.13	0.03	−4.51	0.000	−0.19	−0.08
Class 2
Degree of protection
None (ref)
71% against cervical cancer	0.24	2.38	0.10	0.918	−4.42	4.91
71% against cervical cancer and 90% against genital warts	1.42	2.06	0.69	0.490	−2.62	5.47
90% against cervical cancer and 90% against genital warts	−0.16	2.84	−0.06	0.955	−5.72	5.40
Duration of protection (per year)	−0.06	0.05	−1.14	0.252	−0.16	0.04
Risk of serious side effects (per higher level of risk)	−1.16	0.97	−1.19	0.234	−3.06	0.75
Risk of mild side effects (per higher level of risk)	1.29	1.63	0.79	0.431	−1.92	4.49
Cost (per 1000 CNY)	−0.25	0.24	−1.03	0.305	−0.73	0.23
Class membership model
Score of HPV knowledge	0.37	0.09	4.02	0.000	0.19	0.54
Score of sociopsychological pressure	0.02	0.01	2.98	0.003	0.01	0.03
Age	−0.03	0.11	−0.24	0.810	−0.24	0.19
Living expenditure per month is 1000–2000 CNY (<1000 CNY as ref)	0.26	0.55	0.48	0.632	−0.81	1.34
Living expenditure per month is ≥2000 CNY (<1000 CNY as ref)	0.26	0.60	0.43	0.664	−0.92	1.44
50% of monthly living expenditure from family (mainly from the family as ref)	0.04	0.64	0.07	0.945	−1.20	1.29
Most of monthly living expenditure from themselves (mainly from the family as ref)	−0.21	1.16	−0.18	0.860	−2.48	2.07
High school and above of parents’ education (below high school as ref)	0.34	0.33	1.04	0.299	−0.30	0.98
Ever had a sex life (no as ref)	0.04	0.42	0.11	0.914	−0.77	0.86
Constant	−0.95	2.48	−0.38	0.702	−5.81	3.91

SE indicates standard error. CI indicates confidence interval. CNY indicates Chinese yuan, and 1 CNY =  0.145 USD in 2019.

*The model had a significantly better fit with 2 classes (BIC = 1644.7, McFadden R² = 0.20).

Using the vaccine attribute levels for bivalent, quadrivalent, and nonavalent HPV vaccines in China (Table 4), the predicted vaccine uptake was 11%, 10%, 22% and 58% for bivalent (Cecolin), bivalent (CERVARIX), quadrivalent (GARDASIL®), and nonavalent (GARDASIL 9) HPV vaccines, respectively, among female college students in class 1 who preferred to choose HPV vaccination. In those who had been vaccinated or made an appointment, the percentages choosing bivalent (CERVARIX), quadrivalent (GARDASIL®), and nonavalent (GARDASIL 9) HPV vaccines were 8.0%, 10.1% and 79.0%, respectively. (In total, 2.9% chose an unknown type, and the bivalent (Cecolin) HPV vaccine was not available when the survey was conducted.)

Table 4. Vaccine attribute levels and the predicted vaccine uptake for bivalent, quadrivalent, and nonavalent HPV vaccines in Zhejiang Province, China^*

	Bivalent HPV vaccine (Cecolin)	Bivalent HPV vaccine (CERVARIX)	Quadrivalent HPV vaccine (GARDASIL®)	Nonavalent HPV vaccine (GARDASIL 9)
Degree of protection	71% against cervical cancer	71% against cervical cancer	71% against cervical cancer and 90% against genital warts	90% against cervical cancer and 90% against genital warts
Cost (CNY)	1100	1800	2500	4000
Predicted vaccine uptake	11%	10%	22%	58%

*We assumed that the duration of protection and the risks of serious and mild side effects were the same among the four types of HPV vaccines. CNY indicates Chinese yuan, and 1 CNY = 0.145 USD in 2019.

A total of 98.8% of the respondents chose vaccination in vaccine-related scenes and still chose vaccination in service-related scenes. Ways of making an appointment, number of weeks waiting for vaccination, service time for vaccination, time to the nearest vaccination site, and added cost all had impacts on choice probability (for more details, please see Table 5). The WTP of making an appointment through school, by phone and by the internet compared to on-site is 291.4 CNY (approximately 42.3 USD), 241.7 CNY (approximately 35.0 USD) and 203.6 CNY (approximately 29.5 USD), respectively. The respondents would like to pay 121.9 CNY (approximately 17.7 USD) more to have the service on both weekdays and weekends. They would like to pay 25.0 CNY (approximately 3.6 USD) less if they needed to wait one more week for vaccination after the appointment. Time to the nearest vaccination site also mattered. Compared to within 30 minutes, they would like to pay 171.1 CNY (approximately 24.8 USD) less if the time is between 30 and 60 minutes, and 297.9 CNY (approximately 43.2 USD) less if the time is more than 60 minutes.

Table 5. Regression coefficients of service-related attributes based on responses to a survey investigating preferences for HPV vaccination among female college students in Zhejiang Province, China (n = 733)^*

	Coefficient	SE	z	P > z	95% CI		WTP (CNY)
Ways of making an appointment
On site (ref)
By phone	0.422	0.138	3.07	0.002	0.152	0.691	241.7
By the Internet	0.355	0.162	2.19	0.029	0.037	0.674	203.6
Through school	0.509	0.140	3.63	0.000	0.234	0.784	291.4
Number of weeks waiting for vaccination (per week)	−0.044	0.006	−7.16	0.000	−0.056	−0.032	−25.0
Service in weekdays and weekends for vaccination (weekdays only as ref)	0.213	0.081	2.62	0.009	0.054	0.372	121.9
Time to the nearest vaccination site
<30 minutes (ref)
30–60 minutes	−0.299	0.121	−2.46	0.014	−0.536	−0.061	−171.1
≥60 minutes	−0.520	0.128	−4.08	0.000	−0.770	−0.270	−297.9
Added cost (CNY)	−0.002	0.001	−3.44	0.001	−0.003	−0.001

SE indicates standard error. CI indicates confidence interval. WTP indicates willingness to pay. CNY indicates Chinese yuan, and 1 CNY = 0.145 USD in 2019.

* Approximately 98.8% of all the respondents who chose to vaccinate in the vaccine-related choice set also chose to vaccinate in the service-related choice set. They were included in this analysis, and 9 respondents (1.2%) who chose not to receive the vaccine in service-related scenes were excluded to improve the analysis efficiency.

Discussion

The study quantified the preferences of female college students for HPV vaccination in Zhejiang Province, China. Knowledge of HPV and level of sociopsychological pressure impacted the intention to take the vaccination. Degree and duration of protection, risk of serious side effects, and cost predicted probabilities for uptake of different types of HPV vaccines. Once the respondents decided to take the vaccination, service-related attributes such as appointment ways, waiting time after appointment, service time and time to the vaccination site all affected their WTP for the service.

HPV vaccines have not been introduced into the NIP in China, which means there are no national recommendations or coverage goals or financial guarantees for HPV vaccination. It is determined by the preferences of the target population regarding whether to take the vaccination. Our study implies that higher knowledge of HPV and higher levels of sociopsychological pressure on the targets to some extent lead to higher willingness to take the vaccination, regardless of which type of vaccine they will finally choose. Other studies also demonstrated the positive impacts of HPV knowledge.^30–32

For choosing vaccines, vaccine-related attributes such as the degree and duration of protection, risk of serious side effects, and cost influence the choices. However, considering the similar protection duration and serious side effect rates reported officially, only the degree of protection and cost differentiate the uptake probabilities of the four types of HPV vaccines in the Chinese market.

Previous DCE studies for HPV vaccination mainly focus on vaccine-related attributes.^17–19 This study also chose the attributes most related to HPV vaccination delivery in China and quantified the WTP for these attributes. For female college students, making an appointment through school has a high WTP, which is 291.4 CNY (approximately 42.3 USD) compared to on-site. Female college students would like to pay 121.9 CNY (approximately 17.7 USD) more to have the service on both weekdays and weekends and 25.0 CNY (approximately 3.6 USD) more to wait one less week. Compared to reaching the nearest vaccination site within 30 minutes, they would like to pay 171.1 CNY (approximately 24.8 USD) less if the time is between 30 and 60 minutes and 297.9 CNY (approximately 43.2 USD) less if the time is more than 60 minutes.

The WHO is developing a global strategy for the elimination of cervical cancer as a public health problem and has raised the 90–70–90 intervention coverage targets that need to be met by 2030 (scale-up of HPV vaccination to 90%, twice lifetime cervical screening to 70%, and treatment of preinvasive lesions and invasive cancer to 90%).^2,33 However, even in developed countries that implemented HPV immunization programs, only 33.6% (95% CI 25.9–41.7) of females aged 10–20 years received the full course of HPV vaccine.⁵ In China, there are more challenges. In the free market, supplies chase profits. Girls and women who are better off or in more developed areas have more chances to get vaccinated, leaving those impoverished or in undeveloped areas with a high risk of HPV infection and unprotected from cervical cancer. In addition, the eagerness for receiving the four types of HPV vaccines is extremely uneven, even though a WHO vaccine position paper points out that current evidence suggests that licensed HPV vaccines have relatively similar effectiveness in preventing cervical cancer.⁴ In our study, the estimated uptake percentages of female college students for bivalent (Cecolin), bivalent (CERVARIX), quadrivalent (GARDASIL®), and nonavalent (GARDASIL 9) HPV vaccines were 11%, 10%, 22% and 58%, respectively. According to the estimation, the supply of a nonavalent HPV vaccine is far from adequate in China. More Chinese targets looked for scarce quadrivalent (GARDASIL®) and nonavalent (GARDASIL 9) HPV vaccines rather than the bivalent HPV vaccines, paying higher prices or waiting more time.⁸

Considering the high cervical cancer burden in China, it is necessary to improve the coverage and equality of HPV vaccination. As our study indicates, the first step is to change minds. Proper knowledge of HPV should be disseminated through health education to make the public realize the necessity of HPV vaccination and to make them rationally choose different types of HPV vaccines considering the supply-demand imbalance situation: being vaccinated earlier may be more important than being vaccinated with a HPV vaccine offering a higher degree of protection. In addition, specific delivery strategies should be considered according to the target population. For college students, it may be more efficient to deliver the service through schools. Cost is one of the most important factors when the targets choose different kinds of HPV vaccines. Financial incentives may improve HPV vaccine uptake compared to usual practice.¹⁶ It is suggested that out-of-pocket expenses of vaccination should be reduced by medical insurance or by introducing the vaccine to the NIP in China to improve coverage.

There are some limitations of our study. Our study found that preferences for HPV vaccination were related to knowledge of HPV and level of sociopsychological pressure in female college students. The two colleges were conveniently sampled to make the results mainly representative for these two colleges. In addition, the respondents in our study were relatively better off because more than 90% of them had living expenditures per month more than 1000 CNY (approximately 145 USD). Thus, they may have a higher knowledge level and WTP. The vaccine-related and service-related attributes were separated into different choice sets. This approach may be slightly different from putting all of the options in one choice set. It is supposed that when the respondents chose HPV vaccination, they first cared about the vaccine-related attributes and then the service-related attributes. It also may be a heavy cognitive load for them to consider all the attributes at once. Nine of the respondents chose not to receive the vaccine in the service-related scenes. The number is too small to analyze further why they chose the opt-out choice, and a qualitative study may be done later.

In the free-market context of HPV vaccination in China, higher levels of HPV knowledge and sociopsychological pressure led to a higher probability of HPV vaccination uptake. Vaccine-related attributes impact which types of HPV vaccines are preferred, and service-related attributes impact the WTP for HPV vaccination delivery. It is necessary to disseminate proper knowledge of HPV and develop specific HPV vaccine delivery strategies to improve coverage and equality.

Disclosure of potential conflicts of interest

The authors declare no potential conflicts of interest associated with this manuscript.

Additional information

Funding

This work was supported by the Medical Health Science and Technology Project of Zhejiang Provincial Health Commission [2018KY333].