Public willingness to receive chlamydia, gonorrhea, syphilis, and trichomoniasis vaccines: a scoping review

We collected 2,259 texts of interest from our database searches. 803 were excluded because they were duplicate copies, and another 1,387 were excluded after the title and abstract review process. Of the 69 texts that went through full-text reviews, eight met inclusion criteria (Fig. 1).

Most texts were excluded because they did not meet inclusion criteria, usually because they did not examine at least one of the diseases of interest, did not examine vaccine acceptability, or did not examine the vaccines of interest in human populations. One-hundred additional texts were excluded because they were not published in English. Two texts were excluded because they presented the same results as other included texts in the form of pre-publication conference abstracts [29, 30]; in both instances, the abstracts were excluded while the full articles were included. Two more texts were excluded because they did not specify an STI but instead referred more abstractly to overall STI vaccine acceptability [31, 32]. One other paper was excluded because it assessed the perceived “importance” of a vaccine rather than participants’ “willingness” to receive the vaccines [33].

The majority of included studies were conducted and published in either the United States or Canada, though the country of investigation was unclear in three studies (Table 2). The authors of each of those three studies were affiliated with institutions in the United States (Table 2). The texts’ survey populations included parents of children or parent-adolescent pairs [36, 40, 41], men who have sex with men (MSM) [34], adolescents and young adults from a Pelvic Inflammatory Disease (PID) trial [35], incarcerated women [37], HPV-vaccinated women [38], and STI clinic users [39]. The participants for all of the included studies were either sampled from healthcare settings, participant pools from larger health-related studies, or both (Table 2). For example, Bonny et al.’s 2007 study on incarcerated women’s willingness to receive gonorrhea vaccines was nested in a alcohol use and Human Immunodeficiency Virus (HIV) risk behavior reduction trial [37].

We conducted critical appraisals concurrently with abstraction. Criteria included whether or not inclusion and exclusion criteria for participants were clearly defined; whether or not the study setting and participants were well described, including study time and location; whether or not it was clear how vaccine acceptability was measured and whether or not information on the survey tools’ sources or development were provided; and whether or not appropriate statistical analysis were used, including a probability measure of a Type I error (e.g., p-value or confidence interval) [Additional File 2] [27]. While most texts were missing at least one assessment component, no text had to be excluded because it did not meet any of our assessment criteria [Additional File 2]. Texts most often omitted an explanation of what survey tool they used to assess vaccine acceptability or how they developed their acceptability question(s)–thus not speaking to their tools’ validity–or they did not provide a precision or dispersion measure for their vaccine acceptability estimates [Additional File 2].

Each of the eight included texts describe cross-sectional studies [34‐41]. Six are journal articles [34, 37‐41] while two are abstracts [35, 36], and all of the studies were published since 2000 (Table 2). Interestingly, the papers seem to be clustered at different time intervals, with half published between 2002 and 2007 and half published between 2016 and 2022. This is likely due to the fact that several of the papers have overlap in authorship or come from related studies. Zimet et al. (2002)’s population [36], specifically, is a subset of Zimet et al. (2005)’s population [41], which includes both Zimet et al. (2002)’s participants as well as additional participants recruited afterwards. After deliberation, the review team decided that because their results were distinct, both were eligible for inclusion.

The majority of included studies examined gonorrhea vaccine acceptability, three examined chlamydia, and two examined syphilis (Table 2). None of the included texts presented trichomoniasis vaccine acceptability in their results, though both de Waal et al. (2022) and Plotnikoff et al. (2020)’s supplemental materials showed questions about trichomoniasis in their survey materials [38, 39].

The presentation of results varies between studies, with some reporting percentages of the participants who would accept a vaccine or not, the percentages of the participants who fall in different willingness categories, the average vaccine acceptability scores across participants, or a combination of these indicators (Table 2). All of the studies indicated relatively high acceptability for their respective vaccines, though most do not present variance or confidence estimates (Additional File 2).

Abara et al. (2022) found that 63.6% of MSM respondents were very willing to accept a gonorrhea vaccine, 19.9% were somewhat willing, 7.5% were neither willing nor unwilling, 5.1% did not know, 1.5% were somewhat unwilling, and 2.4% were very unwilling (Table 2) [34]. Zimet et al. (2002) reported that both parents’ acceptability of a gonorrhea vaccine for their child and adolescents’ acceptability of a gonorrhea vaccine was, on average, > 4 points on a five point scale where higher scores indicate higher acceptability [36]. Zimet et al. (2005)’s later publication on an expanded participant pool found that 85.3% of parents agreed or strongly agreed they would get their child vaccinated against gonorrhea and 89.0% of adolescents agreed or strongly agreed they would get vaccinated against gonorrhea [41]. Meanwhile, Mays et al. (2004) found that a slightly more modest 76% of parents would accept a gonorrhea vaccine for their child [40]. Bonney et al. (2007) found that among their sample of incarcerated women, 79% were willing to accept a gonorrhea vaccine [37], while 78.3% (95% CI 75.7–80.7) of de Waal’s sample of HPV-vaccinated women [38] and 76% of Plotnikoff et al. (2020)’s STI clinic-users indicated interest in a gonorrhea vaccine [39].

Only Trent et al. (2016), de Waal et al. (2022), and Plotnikoff et al. (2020) reported chlamydia vaccine acceptability. Trent et al. (2016) found that 93% of their adolescent and young adult sample were willing to receive a chlamydia vaccine [35], while 80.3% (95% CI 77.8–82.6) of de Waal et al. (2022)’s sample [38] and 74% of Plotnikoff et al. (2020)’s sample [39] were interested in receiving a chlamydia vaccine (Table 2).

Plotnikoff et al. (2020) and de Waal et al. (2022), which have considerable overlap in authorship and the latter of which adapted the survey used in the former, were the only two studies to examine syphilis vaccine acceptability [38, 39]. Plotnikoff et al. (2020) found that 76% of participants were interested or very interested in receiving a vaccine for syphilis, while 78.2% (95% CI 75.6–80.6) of de Waal et al. (2022)’s participants were interested or very interested in receiving the vaccine.

As shown in Table 3, four of the included studies used either paper or digital questionnaires to assess vaccine acceptability, and four used interviews, one of which was recorded and self-administered [41].

For the studies whose questions were available, most used the terms “willing”, “willingness”, or “interest” to characterize participants’ attitudes towards receiving a vaccine(s) (Table 3). Scales ranged from five-point to twelve-point Likert scales that represented participant willingness, acceptance, interest, or agreement, and several were dichotomized during analysis to create a binary variable that represented willingness and unwillingness to receive vaccines.

Several studies also assessed factors associated with willingness and reasons for acceptance. All of the studies examining parental opinions found that child age did not significantly impact parental willingness to have their children vaccinated against gonorrhea [36, 40, 41]. However, while Zimet et al. (2002) and Zimet et al. (2005) found that parental education did not have a significant impact on vaccine acceptability [36, 41], Mays et al. (2004) found that parents with lower education were more likely to be accepting [40]. Both Zimet et al. (2005) and Mays et al. (2004) agreed that parents utilizing public health clinics were significantly more likely to have their children vaccinated than those using private practices [40, 41].

Abara et al. (2022) reported that among MSM, younger men and men with a high school diploma/GED or higher education were significantly more likely to receive a gonorrhea vaccine, but no significant differences emerged by race [34]. Abara et al. (2022) also found that men who reported condomless anal sex (CAS), preexposure prophylaxis (PrEP) use, having HIV, testing for a bacterial STD, or having a bacterial STI in the past 12 months were more likely to receive a gonorrhea vaccine. Trent (2016) similarly found that adolescents with a history of chlamydia were more likely to receive a chlamydia vaccine [35].

Bonney et al. (2007) found that in their sample of incarcerated women, demographic characteristics like age, race, and education were not correlated with vaccine acceptability, but psychosocial vaccine correlates like a greater perceived severity of gonorrhea, a greater vulnerability to gonorrhea, and lower vaccine fear were positively associated with vaccine acceptance [37]. Both Plotnikoff et al. (2020) and de Waal et al. (2022) found that participants’ desire to protect themselves and their partners were the first a second most important factors driving acceptability [29, 30], while Mays et al. (2004) similarly found that a desire to protect one’s children and others and concern about disease characteristics were frequently cited by accepting parents [31]. Plotnikoff et al. (2020) and de Waal et al. (2022) both also found potential vaccination cost to be the most frequently identified barrier to vaccination [38, 39].

When examining topics around vaccine guidance and receipt, Trent et al. (2016) reported that health care providers were the most significant sources of vaccine recommendation for participants, ahead of parents, friends, and partners [35]. Abara et al. (2022) similarly reported that participants preferred locations to receive a gonorrhea vaccination would be their primary care provider’s office or an STI clinic [34], which is supported by Plotnikoff et al. (2020), who reported that STI clinics were their participants’ preferred place to receive a vaccine [39].