Preplanned Studies: Willingness of Caregivers to Have Their Children Vaccinated with Pneumococcal Vaccines in the Context of an Innovative Immunization Strategy — Weifang City, Shandong Province, 2021

Pneumococcal diseases (PDs) pose a serious health threat to children (1). Vaccination is the most cost-effective intervention to prevent PDs (2). However, vaccination coverage of pneumococcal vaccines, which has not been introduced into the National Immunization Program (NIP) in China, is rather low among Chinese children (3). The cost of vaccines and the opinions of caregivers toward non-NIP vaccines are important factors that influence vaccination coverage (4). Exploring efficient strategies for increasing coverage of non-NIP vaccines is a crucial initiative for public health.

To improve pneumococcal vaccination coverage and reduce the burden of PDs, starting in June 2021, the government of Weifang City (directly under the jurisdiction of Shandong Province) implemented a policy of providing 1-dose of 13-valent pneumococcal conjugate vaccines (PCV13) at no charge to families for children aged 6 months to 2 years in registered households. Although the free dose does not necessarily have to be the first dose of PCV13, due to the limited financial capacity of the government, the cost of the remaining doses in the series must be borne by caregivers as voluntary vaccination. The Weifang program is the first in the mainland of China for PCV13. Our study investigated caregivers’ willingness to vaccinate their children with pneumococcal vaccines under this one-free-dose policy and explored factors associated with acceptance.

There are 3 PCV13 manufacturers with market authorization in China, 2 of which are domestic. PCV13 is normally given in a multi-dose series in a schedule that varies by the child’s age at the first dose. For example, 4 doses of PCV13 are recommended for full protection when starting at 3 months of age or younger, but only 1 dose is recommended when starting at 2 years of age or older. To avoid the influence of different immunization schedules for PCV13, we restricted the study population to children eligible for the full four-dose series of PCV13. Because our target population was infants younger than 3 months of age, we recruited caregivers as respondents, excluding those who were unable to determine the child’s vaccinations.

The target sample size was determined by the formula, $ \mathrm{N}=\dfrac{{\mathrm{Z}}_{1-\mathrm{\alpha }/2}^{2}\mathrm{p}(1-\mathrm{p})}{{\mathrm{d}}^{2}} $. A previous study showed that the caregivers’ willingness to vaccinate children with pneumococcal vaccines was between 37.9% and 89.1% in China (5), which is a large range. We conservatively assumed P=50%, the allowable error at 3%, and α=0.05. To allow for attrition, we increased the sample size by 10%, yielding a target sample size of 1,174.

The research team designed the questionnaires after discussing with project members and experts in related fields, and revised them after the pilot investigation. We obtained data on demographics, perceptions of the safety and effectiveness of vaccines, perceptions of the risk and seriousness of pneumonia, whether health workers (HWs) recommended pneumococcal vaccines, and whether caregivers trusted HWs. The questionnaires were administered by trained interviewers using portable Android devices to reduce input errors and missing values. We selected at random 30% of completed questionnaires for review each survey day.

Face-to-face and telephone interviews were conducted. During one working day in a clinic, caregivers who met the inclusion criteria were invited to participate in the interview. If the day’s sample size target was not finished, we conducted a telephone survey of the children’s parents with consent. Due to the impact of COVID-19, some vaccination clinics were unable to enroll the target sample size. To reach the overall target sample size, we increased survey sites based on the geographical location of each vaccination clinic and the number of children it served.

The study analyzed all data using SAS software (version 9.4, SAS Institute, Inc. Cary, NC, USA). Counts were expressed as n (%), and Chi-square tests and the Wilcoxon rank-sum test were used for comparisons. A multivariable logistic regression model was used to identify factors related to the caregivers’ willingness. We chose independent variables using stepwise regression. Statistical tests were two-tailed; P<0.05 was considered significant.

Between July 17 and August 3, 2021, we conducted a survey in 57 vaccination clinics across 12 counties/districts. During this time, 1,195 caregivers were surveyed; 90.79% (1,085/1,195) of the questionnaires were completed and considered valid. Among the valid questionnaires, 72.35% (785/1,085) were face-to-face and the rest were via telephone. We conducted Chi-square analyses comparing caregivers’ willingness and demographics by whether the survey was face-to-face or over telephone, and found no statistically significant differences Supplementary Materials.

Mothers, fathers, and grandparents were 62.58% (679/1,085), 36.31% (394/1,085), and 1.11% (12/1,085) of the participants. The average age of the parents was 31.26±4.88 years old. Among all participants, 70.51% (765/1,085) were willing to have their infants receive pneumococcal vaccines. Factors associated with greater willingness included perception of the importance of vaccination, having an HWs recommendation for vaccination, trust in the vaccine information provided by HWs, awareness of the PCV13 policy in Weifang, and other significant factors (Table 1).

According to Table 2, caregivers who believed that vaccination was important (OR=3.96, 95% CI: 1.92–8.20), who received vaccination recommendations from HWs (OR=2.09, 95% CI: 1.11–3.93), and who trusted vaccine information provided by HWs (OR=1.92, 95% CI: 1.08–3.41) were more likely to have their infants vaccinated.

Table 3 shows factors related to hesitancy or refusal to accept pneumococcal vaccines. The top three factors were being unfamiliar with pneumococcal vaccines, lacking confidence in the effectiveness of pneumococcal vaccines, and worrying about adverse reactions.