According to our research conducted in April 2021, 62% of Poles, 33% of Romanians, and 40% of Slovenians who were unvaccinated had the intention to get vaccinated. Combining this with vaccination data in April 2021 [16], this indicates that 5 months later we could expect Poland to reach a vaccinated population (with at least one dose of COVID-19 vaccine) level of 40%, Romania at 28%, and Slovenia at 27%. For Poland, this is almost 12 points below the actual vaccination rate (52%), and for Slovenia, it is 24% points below the actual vaccination rate (51%), while for Romania, it almost exactly matches the vaccination rate five months later (28%).

These results could be explained by the changes in vaccination attitudes after April 2021, which might indicate that Poland and especially Slovenia have had a vaccination campaign that, to some extent, affected public opinion. However, there was a constant struggle to combat misinformation while focusing on preventing the transmission of the virus. Even in April 2021, based on the results of our vaccination intention survey, it was anticipated that the herd-immunity goal would not be reached by the upcoming autumn COVID-19 wave without a more target-focused and effective vaccination strategy, especially in Romania. Hence, our study aimed to offer insights into the factors influencing COVID-19 vaccination intention in the Central and Eastern European context. Subsequently, we aimed to derive practical implications to inform region-specific health campaigns in Central and Eastern European countries.

In line with our assumptions, some of the negative attitudes towards vaccination negatively predicted the intention to receive the COVID-19 vaccine (H1a supported). Specifically, mistrust of the vaccine’s benefits was a significant predictor in all three countries, while concerns about commercial profiteering only had a significant effect in Poland. No effect could be demonstrated for concerns about possible unforeseen effects or the preference for natural immunity. The study shows that at the onset of the pandemic, the fear that vaccines do not bring benefits, and, on the contrary, they can be potentially harmful seems to be one of the most influential factors for the vaccination decision. The fact that Poland was the only country where concerns about commercial profiteering were a significant predictor may be the result of the general distrust of pharmaceutical companies and their activities. According to Ipsos, only 28% of Poles think that pharmaceutical companies are trustworthy [41]. Regarding hesitance towards COVID-19 vaccination, their main concern was a lack of trust in pharmaceutical companies related to the too rapid introduction of a product to the market [42].

We did not confirm the relationship between a conspiracy mentality and the intention to take the COVID-19 vaccine (H1b not supported). The absence of a relationship may stem from our assessment of this phenomenon as general beliefs not specifically associated with theories related to COVID-19 and vaccination. Some research also suggests that, rather than the direction proposed by us, the relationship may be the opposite. Initial hesitancy about being vaccinated may motivate people to seek reasons not to get vaccinated, which they may find in COVID-19 conspiracy theories [43, 44].

We confirmed that a preference for mRNA vaccines positively predicts the intention to vaccinate in a general group (H2 supported). However, we also discovered that countries differed in terms of preferences for the type of vaccine. Only in Poland, the exclusive preference for mRNA vaccines positively predicted the intention to vaccinate. This aligns with previous Polish studies that revealed Poles widely accepted mRNA vaccines [17]. In Poland, mRNA vaccines received more attention from the media and expert groups, shedding light on their mechanisms of action. This likely contributed to a higher level of acceptance of this type of vaccination. On the contrary, AstraZeneca (vector vaccine) received a less favourable reception among the Polish population due to emerging information about possible side effects occurring after the first dose (with mRNA vaccines, these effects were also present but tended to occur more frequently after the second dose) [17]. In Romania, only the mixed vaccine preference had a significant effect, while in Slovenia, neither effect (for mRNA preference nor mixed preference) was significant. The lack of effect in Slovenia might be due to the fact that at the start, mRNA vaccines were exclusively administered to individuals aged 65 and over, with the AstraZeneca vaccine being limited to those aged between 18 and 64 [45]. Official recommendations for mRNA vaccines in Slovenia only began in October 2021 [46].

Regarding trust in information sources, consistent with findings from some prior studies [22], we did not confirm the relationship between family and friends’ opinions and vaccination intention (H3a not supported). Additionally, religious sources did not seem to exert a significant impact on vaccine intention in this setting (H3c not supported). These results suggest that at the onset of the pandemic, other information sources may be more influential in shaping vaccination intentions. In line with that, we discovered that trust in medical professionals and scientific sources in all three countries positively predicted vaccination intention (H3b supported). However, the lowest coefficient was observed in Poland. In 2021, a YouGov international survey revealed that Poland is the only country where healthcare professionals are not the most trusted group for COVID-19 information [47]. Research on the impact of trust in medicine on Polish citizens’ adherence to recommended behaviors showed that 63.8% of Poles express low or moderate trust in healthcare professionals, vaccines, and medicines [48]. Conversely, the highest coefficient was observed in Slovenia, where trust in doctors is high, as confirmed by studies conducted during the pandemic, in which respondents expressed the most trust in doctors and pharmacists (76%) [49].

What is more, trust in information from official sources also positively predicted intention to vaccinate (H3d supported). This is consistent with previous studies showing that trust in governmental authorities positively predicted various positive health behaviors [50, 51]. However, in Poland, this effect was not significant. Polish society appears to distrust official sources, a trend supported by YouGov studies where Poland showed one of the lowest levels of trust in COVID-19 information from official sources [47]. In our study, the highest coefficient was observed for Romania, which is consistent with other studies indicating that government websites were the most trusted source of information for Romanians during the period studied [52].

Regarding media, our research indicates that individuals who trust information from traditional media are more likely to receive the vaccine (H3e supported). These findings align with previous studies [34], emphasizing the crucial role of traditional media, including television, radio, and the press, in disseminating essential information about the pandemic. Traditional media is generally perceived as more reliable due to its higher level of control and oversight, often in collaboration with official authorities [53]. However, the effect of traditional media did not manifest in Slovenia, which can be attributed to a general distrust of mass media among Slovenians. As studies suggest, this scepticism during the pandemic may stem from contradictions among different media outlets in Slovenia, partly attributed to their diverse political backgrounds [54].

We also demonstrated that trust in digital media negatively predicts the intention to vaccinate (H3f supported), highlighting the capacity of the internet and social media to disseminate misinformation and amplify vaccine hesitancy [34]. However, this was true only for Slovenia. Studies suggest that an important factor in protecting from misinformation on social media is media literacy, and other research shows that Slovenia belongs to of well-performing countries in terms of media literacy [55].

However, after including attitudes and beliefs in the model, the effect of all information source variables on the intention to vaccinate was not significant. It appears that a general mistrust of vaccines is the key factor influencing vaccination intention. This is supported by other research indicating that trust in vaccine effectiveness is strongly associated with the intention to be vaccinated against COVID-19 [56].

There are important limitations to this research. The study concerned three selected countries in Central and Eastern Europe. Future research should be extended to other countries in the region. The study was conducted on a group of previously unvaccinated people. This made it impossible to investigate the motives of those who had already been partially or fully vaccinated during the period considered. Future research may include both vaccinated and unvaccinated respondents for a better understanding of the hesitancy towards vaccination.

Another limitation is the divergences in the methodology due to the country-specific sampling approaches, specifically for Romania, where convenience sampling was used, which can induce a large selection bias. Moreover, we should consider language specifics and differences in the online software tools used for data collection. In addition, the sample sizes in Poland and Romania were much lower than those in Slovenia, which means a larger margin of error in the estimates. The results of multivariate analysis are based on a cross-sectional design and thus should be taken as exploratory and correlational.

Based on previous research, we included numerous control variables to ascertain the net effect of the key variables under investigation; however, we cannot exclude the possibility of any remaining common factor. Additionally, without longitudinal or experimental data, the causal order of the variables cannot be ascertained.

Based on the results and conclusions of our study, we provide some practical implications to assist in implementing more effective and efficient health messaging strategies and campaigns targeting groups reluctant to receive the COVID-19 vaccine in Poland, Romania, and Slovenia. Since the attitude based on mistrust of vaccines has proven to be a strong predictor of the intention to get vaccinated, communication campaigns about vaccinations should focus on presenting the benefits of vaccination. Various recent studies also support this notion [56]. Instead of combating conspiracy beliefs to increase vaccine acceptance, our results suggest focusing on disseminating positive information about the effectiveness of vaccines and their benefits. However, as for Poles concerns about commercial profiteering predict vaccination intention, it is also important to present messages aiming to reduce the distrust of pharmaceutical companies and their activities. This involves showing transparency in the operations of these companies and promoting and informing about therapeutic successes. This is also consistent with another finding from our study regarding the preference for a type of vaccines, indicating that effective communication about producers and vaccine types is also crucial in shaping public attitudes, especially at the beginning of the pandemic. When new drugs preventing the spread of a pandemic emerge, a lack of proper information and appropriate promotion can deepen vaccine hesitancy [57].

In terms of social influences our study demonstrates the importance of medical professionals and scientists information. It is crucial to promote scientific evidence and present educational campaigns by professionals, as they are considered the main source of influence on the key determinants of vaccination. Also, official sources are influential for obtaining reliable information [31, 32]. However, in Polish society, there is no relationship between trust in official sources and the intention to vaccinate. This lack of trust in official sources might suggest a danger to health behaviors. Therefore, it is important to work on building trust in the government and identifying communicators within the government who are socially trusted, especially in Poland.

Additionally, public health communicators must decide which media platforms to use for sharing information on COVID-19, considering their credibility. Traditional media appears to be a better choice than social media, given the spread of misinformation and the influence of filter bubbles, which can affect people’s opinions [34]. Nonetheless, in the context of Slovenia, with no significant effect on traditional media and a significant negative effect on digital media information, the communication dynamics present an intriguing case with distinctive patterns. The results suggest that relying on official sources for communication, extending beyond the scope of digital media alone, emerges as the optimal current strategy for vaccination in Slovenia.

To sum up, considering the array of solutions implemented worldwide in response to the pandemic threat, it is imperative to direct attention primarily towards public health services. The crucial aspect of health policy guidance involves the necessity to tailor the solutions implemented, and more importantly, the narrative and communication with society, to the prevailing social, cultural, and historical conditions in each country. In order to achieve this, it is essential to delve into the factors influencing COVID-19 vaccination intention, which, as indicated by our research, could provide insights for communication strategies.