Pay-it-forward 23-valent Pneumococcal Polysaccharide Vaccination Among Older Adults in China: A Two-arm Parallel Randomized Controlled Trial Protocol

doi:10.21203/rs.3.rs-5226301/v1

Background: The 23-valent pneumococcal polysaccharide vaccine reduces the risk of adults developing pneumonia by 38-46%. However, only a small number of older adults in resource-limited parts of China have received pneumococcal vaccination. Pay-it-forward is a social innovation that offers participants free or subsidized health services and a community-engaged message, with an opportunity to donate to support the next recipients. This trial aims to assess the effectiveness and cost-effectiveness of the pay-it-forward intervention in encouraging the uptake of 23-valent pneumococcal polysaccharide vaccine in adults aged 60 years and older.

Methods: A two-arm parallel randomized controlled trial will be conducted in four community health centres in Nanning City, Guangxi Province, China. We will use a randomized block group design. A total of 204 older adults will be randomly allocated in a 1:1 ratio to either the pay-it-forward group or the standard-of-care group. Each participant will complete an online questionnaire. The standard-of-care group will be required to pay for the vaccine by themselves, whereas the pay-it-forward group will receive a 20.7 USD (150 RMB) vaccination subsidy, postcards, and the opportunity to donate. Participants in both groups will be followed up in the second and fourth week after enrollment. The primary outcome will be the uptake of 23-valent pneumococcal polysaccharide vaccine as determined by administrative data. Secondary outcomes include costs, pneumococcal vaccination knowledge, attitudes toward the vaccine, perceptions of gratitude, the incidence of adverse reactions and adverse events, and likelihood of recommending pneumococcal to others.

Discussion: This study will provide evidence on the effectiveness and economic costs of the pay-it-forward strategy for pneumonia vaccination among older adults. The findings could have implications for vaccination policy and offer a new strategy for increasing vaccination in resource-limited areas.

Trial registration Chinese Clinical Trial Registry (ChiCTR), ChiCTR2400079410. Registered January 3, 2024.

Randomized controlled trial

23-valent pneumococcal polysaccharide vaccine

pay-it-forward

older adults

China

Streptococcus pneumoniae poses a significant threat to global health, contributing substantially to morbidity and mortality[1, 2]. Furthermore, it is recognized as the most prevalent bacterial agent that causes community-acquired pneumonia, a condition associated with increased morbidity, mortality, and economic burden, particularly among individuals aged over 65 years[3]. The estimated incidence of community-acquired pneumonia among individuals aged 60 years and older in China was 34.68/1000 person-years in 2016[4]. The hospitalized mortality for patients aged ≥ 65 years with community-acquired pneumonia from January to December 2014 was 5.7%[5]. This underscores the need for pneumococcal vaccines to prevent community-acquired pneumonia.

The WHO and the Chinese Center for Disease Control and Prevention recommend a 23-valent pneumococcal polysaccharide vaccine (PPSV-23) for adults aged 60 years and older[6]. The PPSV-23 has a 30.9% efficacy in preventing community-acquired pneumonia[7] and offers a 70% protective efficacy against invasive pneumococcal diseases[8]. Furthermore, the vaccine’s protective benefits are known to be durable for five years[9]. Despite these advantages, the Chinese government has yet to incorporate PPSV-23 into its free routine immunization program for older adults. Consequently, pneumococcal vaccination remains an out-of-pocket service in China (PPSV23: 220–280 RMB (30.4–38.7 USD)/dose), leading to suboptimal uptake rates among older adults. Only 1–42% of older adults in China received the pneumococcal vaccine[10]. This low uptake of PPSV-23 in China can be attributed to various factors, including financial constraints[11], vaccine hesitancy[12], and poor understanding[13]. In light of these challenges, it is imperative to devise and implement innovative strategies aimed at increasing PPSV-23 vaccination among older adults.

Pay-it-forward is a social innovative intervention aimed at promoting healthcare service utilization[14]. With pay-it-forward, individuals receive a gift, such as a free or subsidized healthcare service, and are then invited to donate money or create a postcard with an encouraging message to support the next healthcare service recipients[15]. This intervention may help alleviate financial barriers that hinder the uptake of the PPSV-23. Additionally, this intervention strategy may lead to positive health outcomes by improving trust and confidence in vaccines[16]. Our previous studies suggested that pay-it-forward interventions significantly increased influenza vaccination among older adults[17], as well as improved HPV vaccination among adolescent girls aged 15–18 years[18].

However, existing research on pay-it-forward mainly focused on more developed cities[17, 19, 20]. Furthermore, there has been no research specifically focused on utilizing pay-it-forward to promote pneumococcal vaccination. This underscores the importance of pay-it-forward in boosting PPSV-23 vaccination in less developed areas.

Guangxi is recognized as one of the resource-limited provinces in China, with the per capita disposable income of households in 94 out of 111 counties in Guangxi being lower than the national average in 2022 (5,091.7 USD)[21, 22]. The pay-it-forward intervention may present a potential solution to increase the vaccination rate of PPSV-23 among old adults in Guangxi. This study aims to conduct a two-arm parallel randomized controlled trial to evaluate the effectiveness and cost-effectiveness of the pay-it-forward intervention in promoting pneumococcal vaccination rates among individuals aged 60 years and above in Nanning City, Guangxi, China.

Participants and public involvement

The public will be involved in creating related materials, such as developing a video explaining the concept of "pay-it-forward" and co-designing postcards to promote vaccination with PPSV-23[17].

Study design and setting

We will conduct a two-arm parallel randomized controlled trial among adults aged 60 years and above. Community healthcare centers (CHCs) will be the unit of randomization and intervention. To recruit participants, we will use vaccination clinics, WeChat, and Short Message Service (SMS). Participants will be randomly allocated to either the self-pay arm (self-payment for vaccinations) or the pay-it-forward arm (receiving 150 RMB (20.7 USD) subsidy for vaccination and opportunities for donation and handwritten postcards) in a 1:1 ratio through an envelope mechanism for every four participants in a block group. Follow-ups are planned for the second week and fourth week after enrollment of participants. At the end of the fourth-week follow-up, we will confirm the number of individuals vaccinated with the PPSV-23 in both groups through the vaccination information management system for the immunization program. Written informed consent will be obtained from each participant before their enrollment. CHCs are the main vaccination units for residents, with sufficient vaccine and medical staff familiar with vaccination procedures, facilitating the recruitment of study participants. To ensure sample representativeness, we plan to conduct this study in Qingxiu district (high-income areas), Xixiangtang district (middle-income area), and Liangqing district (low-income area) in Nanning City, Guangxi Province. All research assistants and community healthcare workers (CHWs) involved in this study will receive the same training. Figure 1 and Table 1 illustrate the study design and interventions.

Table 1 Schedule of events of the pay-it-forward for PPSV-23 study

Event	Eligibility screening	Enrollment	Follow-up		Close-out
Event	Week 0	Week 0 (baseline)	Week 2	Week 4	Week 5
Recruitment and enrollment
Vaccination platform screening	×
Phone or WeChat consultation	×
Recruitment Poster		×
Intervention
pay-it-forward program leaflet		×
Vaccination leaflet of PPSV-23		×
PPSV-23 promotional video		×
Informed consent		×
Group allocation		×
Donation		×
handwritten postcard		×
Baseline questionnaire		×
Follow-up questionnaire			×	×
Assessment
Vaccination rate of PPSV-23					×
Vaccination attitudes					×
Willingness to vaccinate					×
Perceptions of gratitude					×
Recommended vaccination rates for PPSV-23					×
Incidence of adverse events/reactions to vaccination				×
Cost-effectiveness

PPSV-23: 23-valent pneumococcal polysaccharide vaccine.

Table 2 Summary of information to be collected

Item	Questionnaire code(s)
Socio-demographics	A
Knowledge about PPSV-23	A&B&C
Dissemination of PPSV-23	A
Attitudes toward PPSV-23	A&B&C
GQ-6 gratitude scale	A&B&C
Willingness and reasons for receiving the PPSV-23	A
Feasibility, appropriateness, and acceptability of pay-it-forward (only pay-it-forward group)	A
Reasons for promoting or discouraging donations(only pay-it-forward group)	B&C
Incidence of adverse reactions or events	B&C
Recommended PPSV-23 for others	B&C

PPSV-23: 23-valent pneumococcal polysaccharide vaccine; GQ-6: Gratitude Questionnaire - Six-Item Scale

Community engagement

To determine the effectiveness of the PPSV-23 and the benefits of vaccination for community residents, we will cooperate with local CHCs. CHWs will participate in the design of the pneumonia leaflet, refinement of the questionnaire, provision of communication strategies and recommendations in order to enhance the engagement of old adults in this study. Participants will be invited to write postcards for the subsequent participants.

Participants

Eligible participants will be screened for participation in the program with the help of CHC healthcare workers: (1) be 60 years of age or older; (2) meeting the medical requirements for PPSV-23 vaccination; (3) have resided in the community in the past three months; (4) be mentally capable of providing informed consent for vaccination. Participants with any of the following criteria will be excluded: (1) older adults with severe chronic or psychiatric illnesses; (2) older adults with a clinically evaluated risk of allergy to the PPSV-23; (3) older adults who have received PPSV-23 within 5 years.

Randomization

The study designer will employ SPSS software (version 25.0) to generate random numbers based on the sample size. Each set of four random numbers will be grouped as a block group, and numbered in the order of generation. Subsequently, within each block group, the random numbers will be arranged in ascending order. The smallest two numbers will be assigned to the self-pay arm, while the largest two numbers will be assigned to the pay-it-forward arm. Afterward, the study designer will write the corresponding numerical numbers on the surface of opaque envelopes, fill them with material and grouping information, and then seal them. Participants will be given the envelopes corresponding to their numbers in order to participate in the study.

Blinding

Achieving blinding poses a challenge given that both study researchers and participants are aware of the intervention allocation. Nonetheless, several blinding techniques will be employed to mitigate bias: (1) Strict confidentiality of the generation and assignment of random numbers will be maintained among all participants, research assistants, and CHWs, with only the study designer being privy to this information. (2) Research assistants or CHWs responsible for allocating envelopes and participants will not be informed of the group information until the envelopes are opened. (3) The nurse administering the vaccine will not have any knowledge of the grouping of participants. (4) Data analysts will be kept unaware of which intervention participants receive.

Intervention

Pay-it-forward group

Research assistants at the vaccination clinics will use vaccination leaflet of PPSV-23 (Additional file 1) to introduce participants in the pay-it-forward group to Spn, PPSV-23 vaccination and its benefits. Subsequently, they will use pay-it-forward program leaflet (Additional file 2) to explain the purpose of the program, access to the PPSV-23 vaccination subsidy (20.7 USD), the opportunities to donate, and to write a postcard encouraging the next pay-it-forward recipients to get PPSV-23. Participants in this group will be informed the standard cost of the PPSV-23 vaccination (US$29·5–30.0) and the previous pay-it-forward recipients' donations, as well as the hand-written postcards with encourage message for PPSV-23 vaccination. After watching the PPSV-23 promotional video, participants will be surveyed by a research assistant using questionnaire A. They will be asked if they are willing to be vaccinated and if they are willing to make a donation or write a postcard with a message to encourage the next pay-it-forward recipients to get vaccinated with PPSV-23. Participants can donate at the vaccination clinics or online with their enrolled number (The envelope number). The participants will also be informed that their decision to donate, as well as the donation amount, will not affect their eligibility for vaccine subsidies and access to PPSV-23. Participants willing to be vaccinated will be evaluated for vaccination eligibility and scheduled for an appointment. Donations received will be used to help the next pay-it-forward recipients, and the amount and use of donations will be regularly updated on WeChat official account. The CHWs will conduct follow-up surveys using questionnaire B and questionnaire C during the second and the fourth week after enrolment. Each participant will receive a total of 100 RMB (13.8 USD) for completing the three surveys.

Self-pay group

Participants in this group will also receive the same leaflet on vaccination with PPSV-23, a promotional video and a questionnaire (not including questions on pay-it-forward) similar to the pay-it-forward group. They will also be informed of the standard cost of the PPSV-23 (US$29·5–30.0). After watching the PPSV-23 promotional video, participants will be surveyed by a research assistant using Questionnaire A and be informed that they will need to pay for the vaccination at the standard market price. Participants willing to be vaccinated will be assessed for vaccination eligibility and make an appointment for vaccination. Additionally, participants will also be followed up by the CHWs in the second week and the fourth week after enrollment. Participants will receive a total of 100 RMB (13.8 USD) for completing the three surveys. Participants in the self-pay arms will not receive any information about the pay-it-forward.

Sample size

The sample size is calculated by PASS 2021 software after conducting a pilot trial. In the pilot trial, 23 (88. 5%) out of the 26 participants in the pay-it-forward group and 3 (11. 5%) out of the 26 participants in the standard-of-care group received the pneumonia vaccine. Based on the results of the pilot trial, we have calculated the sample size to be 16. However, this sample size was determined too small to detect the desired effect size for the trial. To address this, we looked into previous data on vaccination rates and estimated the difference in rates between the two groups based on prior experience. A previous review indicated that the vaccination coverage of PPSV-23 among old adults in China ranges from about 1.23% to 42.10%[10]. Additionally, our previous pilot showed that pay-it-forward intervention increased influenza vaccination coverage in old adults by approximately 30%[17]. Taking these into account, we estimated a 10% PPSV-23 vaccination coverage in older adults and projected that pay-it-forward intervention would increase this by 20%. The power of the test was taken as 90% using a two-sided test with a significance level of 0.05. The minimum sample size calculated was 158. Considering the 20% dropout rate, the minimum sample size required was adjusted to 198. To accommodate a block-randomized design, the minimum sample size was increased to 204. Consequently, at least 204 samples are needed for the trial.

Data collection and management

When participants are enrolled, the research assistants will record their enrollment time, envelope number, name, identification number, and group. Data will be collected on the professional Chinese questionnaire website Wenjuanxing (https://www.wjx.cn/) using self-designed questionnaires, including the baseline questionnaire A and the follow-up questionnaires B and C. The information collected is presented in Table 2. We will collect the following information: (1) Sociodemographic characteristics (e.g. gender, marital status, education levels, monthly income and employment). (2) Knowledge of PPSV-23 (e.g. age limits, reduced risk of hospitalization and death, reduced medical costs due to pneumonia). (3) Attitudes to PPSV-23, including the use of a standardized scale[23] to assess vaccination confidence among participants in the vaccine (e.g., safety, efficacy, and importance of the vaccine). (4) Education and sensitization related to PPSV-23 (e.g. recommendation of PPSV-23 by healthcare workers or friends). (5) Using the most widespread Gratitude Questionnaire - Six-Item Scale (GQ-6)[24] to measure participants’ tendency to gratitude. (6) Participants in the pay-it-forward group will be asked about the reasons that facilitated and discouraged donations. Besides, the feasibility, appropriateness and acceptability of pay-it-forward interventions will be assessed with previously well evaluated scales[25]. (7) For participants who receive vaccination, we will investigate the incidence of adverse reactions (e.g., fever, redness, swelling, pain, itching) or adverse events (e.g., pneumonia, bronchitis, ear infections). For those participants who will not be vaccinated, we will collect the reasons for declining vaccination. (9) Recommended others to receive PPSV-23.

The uptake of PPSV-23 will be verified using the immunization program's information management system. Separate questionnaires will be conducted for the self-pay group and the pay-it-forward group. Quality control questions have been included to ensure the accuracy of questionnaire completion. Two similar questions will be included in different sections of the questionnaire to assess the consistency of responses (a. Whether vaccination with PPSV-23 reduces hospitalization and deaths? b. Vaccination with PPSV-23 reduces hospitalization and death). If participants gave different responses to these two similar questions, the questionnaire was considered invalid and they will have to complete it again. Once participants are enrolled, personally identifiable information and survey data will be entered into an electronic Excel form. The form will be encrypted by the study designer using a digital password and only the study designer and researcher performing data analysis will have access to it. A Data Safety and Oversight Committee (DSOC) will be established, comprised of two clinicians, an epidemiologist and statistician, and a representative of the Medical Ethics Committee, who will operate independently of the research team. The DSOC will review the process of the study, data collection, management, and analysis process.

Outcome measures

The primary outcome of this study will be to assess the uptake of PPSV-23 in each arm after one month of intervention. Secondary outcomes will be included vaccine confidence, cost per person vaccinated, cost-effectiveness, vaccine knowledge between the two groups, attitudes toward vaccination, willingness to vaccinate, gratitude, recommendation of others for vaccination, and adverse events.

Statistical analysis

Descriptive analysis will be employed to describe the sociodemographic characteristics, knowledge, attitudes, and behaviors of the participants in each arm. Cronbach's alpha test will be used to test the reliability of the scales in the questionnaire. To address missing follow-up data, we will use the last observation carried forward method and multiple interpolations for missing values for categorical and continuous variables. For the primary analysis, we will conduct an intention-to-treat analysis to compare vaccination rates between the two groups. In addition, we will stratify income, presence of chronic disease, and distance from residence to the vaccination site to compare pneumonia vaccination rates between the pay-it-forward group and the standard-of-care group. We will also adjust for sociodemographic information such as age, sex and educational level and use logistic regression to compare vaccination rates between the pay-it-forward group and the standard-of-care group. The results will be reported as crude odds ratios (cORs) and adjusted odds ratios (aORs), along with 95% confidence intervals (95% CI). For secondary analyses, we will perform an economic evaluation by constructing a Markov-based model to assess the cost-effectiveness. Cost for each program element will be collected and a micro-costing approach will be used to evaluate the costs of the self-pay arm and pay-it-forward arm. Other secondary outcomes will be summarized using descriptive statistics and compared between the two arms. All statistical tests will be two-sided tests with a test level of p<0.05.

The prevalence of pneumococcal diseases among elderly adults in China is still high, yet the coverage rate of PPSV-23 in China(1.23%~42.10%)[10] is significantly lower compared to developed countries(52%-75%)[26–28]. In some economically developed cities, such as Beijing, Shanghai, and Guangzhou City, free pneumococcal vaccinations have been implemented for community residents[29]. However, in underdeveloped areas with limited health resources, the government faces challenges in providing free pneumococcal vaccines to community dwellers due to insufficient funding. Therefore, it is imperative to implement effective and feasible interventions to promote vaccination uptake. Previous studies have demonstrated the effectiveness of the pay-it-forward intervention, targeting influenza vaccination or testing for gonorrhea and chlamydia in developed areas of China[14, 17]. However, the effectiveness of this intervention in resource-limited areas has not been studied. This trial will be the first to assess the effectiveness of pay-it-forward intervention in promoting the uptake of PPSV-23 for older adults in low-income areas in China. Additionally, a self-designed questionnaire will be used to assess the differences in cost-effectiveness, knowledge, attitudes, willingness to vaccinate, and perceptions of gratitude between the intervention and control groups. This study may provide insights into the development and optimization of pneumonia immunization strategies in regions with limited resources.

We anticipate this study will provide evidence supporting the feasibility of the “pay it forward” intervention in vaccine services and offer valuable insight for evidence-based practice in future vaccine programs. Currently, PPSV-23 is not included in China's National Immunization Program, requiring individuals to bear the cost of vaccination, which in turn limits the uptake of the PPSV-23 in less developed areas. The “Pay it forward” approach offers the potential to promote vaccination in less developed areas. In the absence of government funding for vaccination, pay-it-forward may effectively pool small donations to support more individuals in accessing pneumonia vaccine services, which is of significant importance for improving vaccination in underdeveloped areas with relatively insufficient health resources. Moreover, the “pay it forward” strategy has demonstrated high cost-effectiveness in promoting influenza vaccination[30]. By evaluating the cost-effectiveness, this study may inform decision-making regarding expansion strategies, enabling stakeholders to make informed resource allocation decisions.

Previous studies have shown that implementation of free vaccination policies has enhanced coverage of PPSV-23[31, 32]. However, implementing free vaccination strategies remains in low-income areas with limited health resources remains challenging. Prior randomized control trials have explored the use of educational information interventions to increase vaccination[33, 34], yet immediate improvements in knowledge and risk perception did not lead to an immediate increase vaccination behavior. Vaccine price, vaccine accessibility, and confidence in vaccines are additional factors influencing vaccination behavior. This study is the first to use a randomized controlled trial to evaluate the effectiveness of the pay-it-forward intervention for PPSV-23 vaccination. Through community engagement, subsidizing of vaccination, and public education, the intervention aims to enhance knowledge about the vaccine, bolster confidence in its safety and efficacy, attract financial contributions, and ultimately promote vaccination.

Some limitations are existed in this study. First, the questionnaires rely on self-reported, which may introduce biases in certain responses. However, this should not impact the vaccination rate, as they will be verified through the vaccination information management system of CHCs. Second, the sample size for exploring factors associated with willingness to vaccination is insufficient, and additional cross-sectional studies with rigorous sampling and a larger sample size are necessary to determine these factors. Third, conducting two follow-up surveys within a month may improve participants’ knowledge of vaccines to some extent, but it may not be sufficient to change their attitudes and behaviors toward PPSV-23 in a short period. Lastly, further qualitative interviews are required to delve into people's perceptions and attitudes towards the “pay it forward” strategy, the mechanisms that promote acceptance of the pay-it-forward strategy, as well as the barriers and facilitators to its implementation.

In summary, this study aims to assess the effectiveness and cost-effectiveness of the “pay it forward” intervention in the vaccination of PPSV-23 among old adults. This innovative payment model may offer a new approach to enhance vaccination uptake in resource-limited regions, ensuring accessibility to vaccination services, especially in settings with limited healthcare resources. Additionally, the pay-it-forward strategy may act as a transitional step towards gradually shifting from individual payment-based vaccination policies to publicly funded ones.

CHCs

Community health centers

CHWs

Community healthcare workers

DSOC

Data Safety and Oversight Committee

GQ-6

Gratitude Questionnaire - Six-Item Scale

PPSV-23

23-valent pneumococcal polysaccharide vaccine

SMS

Short message service

SPn

Streptococcus pneumoniae

Ethics approval and consent to participate

This study was approved by the Medical Ethics Committee of Guangxi Medical University (KY0261) on 5 December 2023. The trial will be conducted by the principles of the Declaration of Helsinki and the regulatory requirements of China. The trial has been registered on the China Clinical Trial Center Website (https://www.chictr.org.cn) with registration number ChiCTR2400079410. Eligible older adults will be required to provide written informed consent for their participation in the study.

Consent for publication

Not applicable.

Availability of data and materials

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Funding

The work was supported by funding by the Guangxi Bagui Young Top Scholar(To Bingyu Liang), Thousands of Young and Middleaged Key Teachers Training Program in Guangxi Colleges and Universities (To Bingyu Liang), the China Scholarship Council (To Bingyu Liang), and the National Natural Science Foundation of China (Grant Nos. 81960615).

Authors’ contributions

BY L, JT co-led the conception and design of this trial. JQ, LJ W, and CX T drafted the manuscript and participated in the study design. JF H, ZF L, and SY Q participated in the design of the questionnaire. QQ S, TH, SM C, and GQ W contributed to the recruitment of participants and the collection of the data. DW, YX G, CY N, WM T, HL, LY made important contributions to the design of the trial and the evaluation of the intervention. All authors contributed to the editing of the manuscript. All authors read and approved the final manuscript.

Acknowledgments

We would like to thank the four community health centers we partnered with, which were integral to the recruitment of study participants for this trial and will be critical to its success.

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The authors declare no competing interests.

Pay-it-forward 23-valent Pneumococcal Polysaccharide Vaccination Among Older Adults in China: A Two-arm Parallel Randomized Controlled Trial Protocol

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Abstract

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Introduction

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Discussion

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