Caregivers and HCPs who met the study inclusion criteria were recruited from pre-existing internet market research panels to participate in a cross-sectional online survey. The markets of Germany, France, Spain, and Greece were chosen to represent a diverse sample of countries within the European Union in lieu of the ability to conduct the study in every country. This is a descriptive study only, and no a priori hypothesis was defined. Therefore, no formal sample size or power calculations were conducted for the study. All eligible participants that met the study inclusion criteria were included in the research and analysis. The target sample size was deemed robust and representative within funding constraints. The request to participate in research was sent via email to members of the panels who had expressed a willingness to participate in research studies. The interview request included a statement of informed consent and the set of screening questions to determine eligibility.

Caregivers and HCPs who expressed interest and were eligible to participate were directed to complete a 10-min online survey. The respondent could choose to quit the survey at any point without penalty. Upon completion of the survey, participants were compensated through their panel with a modest honorarium in line with current fair market values as determined by the study sponsor. Respondents remained blinded to the study sponsor until all questions had been answered, at which time participants were able to request details on the study sponsor, in line with local regulations.

The study (protocol # 2023-0381) was approved by Pearl Institutional Review Board (IRB) of Indianapolis, Indiana, on October 27, 2023. Informed consent was obtained from all participants prior to participating in the study. This article is based on primary data collected from human participants who consented to the study.

Pediatricians in all countries, primary care physicians (PCPs) in France, and nurses in Greece involved in the recommendation and/or administration of vaccines to children aged 0–5 were recruited to participate in the study. PCPs were included in France and nurses in Greece due to their greater involvement in pediatric vaccination in these countries compared to other countries included in the study.

The inclusion criteria for HCPs included: (1) a practicing pediatrician (in all markets) or PCP (in France) or nurse (in Greece); (2) in practice for 3–30 years in an office-based practice; and (3) administered or recommended vaccines to patients.

Exclusion criteria included: (1) unwilling to provide informed consent or to have potential adverse events reported anonymously; (2) required consent from an employer, organization, or professional association to participate in this research, which they had not yet obtained; (3) practiced in a hospital or private clinic; (4) spent less than 75% of their professional time in direct patient care; (5) saw less than 300 pediatric patients per month as a pediatrician or less than 200 pediatric patients per month as a PCP; (6) patients aged 0–5 made up less than 20% of their patient population as a pediatrician or less than 10% of their patient population as a PCP; (7) they had not prescribed or recommended specific pneumococcal vaccines; and (8) they were affiliated with any pharmaceutical company or healthcare manufacturer, serving as a clinical investigator, conducting clinical research, or providing consulting services in any capacity.

Caregivers of children aged 0–5 and expectant mothers were recruited across the four European countries, as per the criteria outlined below.

The inclusion criteria for caregivers were (1) aged 18 to 55 years old; (2) residing in Germany, Spain, France, or Greece; (3) parent or legal guardian of at least one child aged 0–5 or a female currently in the third trimester of pregnancy; and (4) responsible (or shared responsibility) for making decisions concerning the health of their child. Of note, 80% of the participants were required to be aware of the existence of pneumococcal disease (e.g., pneumonia, ear infection, etc.).

Exclusion criteria for caregivers included: (1) unwilling to provide informed consent or to have potential adverse events reported anonymously; (2) consider themselves not at all supportive of vaccines (excluded because questions would not be relevant for these respondents); and (3) currently employed in the advertising/market research, public relations, pharmaceutical, or medical industry.

The following measures were collected from study participants and are included as supplementary material. Survey instruments were translated into local languages, and all respondents completed the survey in their local language. Whereas both HCPs and caregivers responded to the same schedule statements, each group then responded to questions tailored to their role.

HCPs provided basic demographic information, including specialty, involvement in the administration of the vaccination, regional location and setting of practice, gender, years in practice, and monthly patient volume.

HCPs were surveyed concerning the perceived importance of protection from pneumococcal diseases, the level of agreement with pneumococcal disease vaccination, the importance of attributes when considering the PCV dosing schedule, their opinion and perceptions of a 3 + 1 PCV dosing schedule, their likelihood of supporting a 3 + 1 PCV dosing schedule as a national recommendation, their opinion of parent support of a 3 + 1 PCV dosing schedule, the perceived level of burden induced by an extra dose/doctor visit for pneumococcal disease vaccination, and the sources typically relied on for childhood vaccine information.

In the HCP survey, a four-point Likert scale was used to force respondents to have positive or negative opinions. As the HCPs in this survey had all prescribed pneumococcal vaccines, they were familiar with the subject matter, and therefore a neutral option was deemed unnecessary.

Caregivers provided basic demographic information, including gender, type of area in which their primary residence is located (urbanicity), educational attainment, current employment status, household income, and age.

Caregivers responded to survey questions regarding the perceived seriousness of pneumococcal diseases, the importance of vaccination, their agreement on aided statements about pneumococcal diseases, their opinion on PCV schedules that include an additional dose/doctor visit, and their overall agreement with and perceptions on childhood vaccinations and sources typically relied on for childhood vaccine information. In the caregivers survey, a five-point scale was used when measuring to allow a neutral option. As such, direct comparisons between the HCP survey and caregiver survey should be viewed with caution, as the presence or absence of a midpoint option may impact the overall percentage of positive or negative responses.

This study primarily utilized Likert scales to assess respondent agreement with and support for the questions and statements posed. Data for these questions are reported as the percentage (%) of respondents who somewhat or strongly agree with/support the question/statement. Descriptive statistics are presented for study respondents. Data for continuous variables (e.g., age) include the mean and standard deviation (SD). For categorical variables (e.g., gender and employment status), frequencies and percentages are presented.