Discussion
In our study, a high IBV with the booster dose has been observed (88.1%). This figure aligns with similar findings in other parts of the world, where participants have a strong willingness to receive the additional dose with values of 87% of adults in Denmark ( Jørgensen, Nielsen & Petersen, 2022 ), 82.5% of adults in Iran ( Askarian et al., 2023 ), 84.6% of adults in Bangladesh ( Roy, Azam & Islam, 2023 ), 81.2% individuals with chronic diseases in Malaysia ( Abdullah, Ching & Ali, 2023 ) and 82.8% in elderly individuals in China ( Qin et al., 2022b ). Furthermore, our results are comparable to those reported in Chile (88.2%). However, this result contrasts significantly with the situation in Ghana, where only 46.2% of adults have a high intention to be vaccinated (IBV) ( Storph et al., 2023 ). However, a systematic review indicated that the IBV of the booster dose is different from the actual vaccine uptake ( Abdelmoneim et al., 2022 ) . Furthermore, rates of acceptance and hesitation can exhibit variability depending on contextual factors and the dynamics of epidemic waves ( Noh et al., 2022 ). The high IBV in our study probably has two reasons. First, the positive IBV included those who responded in the survey as “definitely yes” and “probably yes” to be vaccinated, indicating a range of willingness rather than absolute acceptance of the booster dose. Secondly, the high IBV may be attributed to the timing of our data collection, occurring one week after the onset of the fourth wave of COVID-19 in Peru ( Salud Con Lupa, 2022 ).

Our results indicate that having a good perception of the effectiveness of the booster dose is strongly associated with a higher IBV (PR:3.69). Studies conducted in China ( Qin et al., 2022b ; Tung et al., 2019 ; Hu et al., 2022 ), Malaysia ( Abdullah, Ching & Ali, 2023 ) and Czech Republic ( Klugar et al., 2021 ), as well as a systematic review ( Abdelmoneim et al., 2022 ), indicated that the perceived efficacy or effectiveness of vaccines was associated with IBV of the booster dose. On the other hand, studies conducted in China ( Lai et al., 2021 ; Qin et al., 2022 ) and countries such as Poland ( Rzymski, Poniedziałek & Fal, 2021 ), Italy ( Folcarelli et al., 2022 ), Greece ( Galanis et al., 2022 ), and Algeria ( Lounis et al., 2022 ) reported that the reasons for refusing to receive the booster dose were uncertainty about its efficacy and the perception that an additional dose was not necessary. It should also be considered that these studies were conducted at different times during the COVID-19 pandemic, which could result in variations in the results, as the perception of the population may have changed over time.

On the other hand, the crude regression analysis indicated that fear of adverse effects of the vaccine is one of the reasons for a lower IBV. This aligns with many studies that concluded that concern about adverse effects was the main factor for refusal or hesitancy to receive a booster dose ( Qin et al., 2022 ; Rzymski, Poniedziałek & Fal, 2021 ; Folcarelli et al., 2022 ; Galanis et al., 2022 ; Lounis et al., 2022 ). However, in the adjusted model, no such association was observed, possibly because this effect may have been overshadowed by the recommendation of physicians and other health professionals. It seems that these recommendations may carry more weight than the fear of adverse effects of the vaccine. Despite various studies supporting the efficacy and safety of the booster dose in preventing COVID-19 ( Bar-On et al., 2021 ; Bar-On et al., 2021 ; Barda et al., 2021 ; Moreira et al., 2022 ) and its variants ( Chenchula et al., 2022 ), achieving good communication and literacy in the population is crucial. This is particularly important when considering the situational context of each country and locality, addressing their main doubts and concerns about the booster vaccine ( Dubé & MacDonald, 2022 ; Lazarus et al., 2021 ). Such efforts are vital for improving vaccination rates in many parts of the world. Our study showed that being a man, compared to being a woman, was associated with a higher IBV. These results are similar with findings in Italy ( Miragliadel Giudice et al., 2023 ), Iran ( Askarian et al., 2023 ) and in a meta-analysis ( Abdelmoneim et al., 2022 ). This could be explained by the higher morbidity and mortality against COVID-19 that men had in Peru ( Ramírez-Soto, Ortega-Cáceres & Arroyo-Hernández, 2022 ), also because women are more susceptible to vaccine conspiracy beliefs ( Sallam et al., 2021 ). However, other studies have shown even higher IBV in women, probably because they are more tolerable to “pandemic fatigue” ( Urrunaga-Pastor et al., 2022 ; Bendezu-Quispe et al., 2022 ; Rzymski, Poniedziałek & Fal, 2021 ; Miao et al., 2022 ).

Regarding age, the only category that was associated with IBV was age 45 years and older, obtaining a lower prevalence compared to age 18 to 29 years. This aligns with findings from other studies that indicate a higher IBV with booster dose as evidenced in Australia ( Allen et al., 2022 ) and Algeria ( Lounis et al., 2022 ). Perhaps, these results can be attributed to a preference bias, as older adults saw early efficacy to early vaccine exposure, because they were prioritized with primary vaccination for having been the most affected at the beginning of the pandemic ( Valladares-Garrido et al., 2022 ). Additionally, another study notes that middle-aged and older age groups may have greater concern for adverse events with an additional dose and thus a lower IBV ( Qin et al., 2022 ). However, other research has reported that older adults have the highest IBV with the booster dose because they are a risk group ( Rzymski, Poniedziałek & Fal, 2021 ; Folcarelli et al., 2022 ).

Additionally, in the multiple regression, we unexpectedly found a slightly higher probability of IBV was found in those who reported some mild-moderate ESAVI compared to those who did not report any. Although this may be due to the fact that people with mild-moderate ESAVI that is not life-threatening and does not cause major harm (such as fever, malaise, headache, muscle aches, etc .), have a better perception of vaccine efficacy because of the same side effects they suffer. However, our measurements may not be entirely correct, as the presence of ESAVI must be rigorously evaluated by a physician or qualified health personnel ( Anonymous , 2023a ). In contrast to a previous study that evaluated primary vaccination ( Herrera-Añazco et al., 2021b ), we found no association between suspected COVID-19 symptomatology and increased IBV with the booster dose, however, it is possible that our results are consistent, since, despite being at the beginning of the fourth wave ( Salud Con Lupa, 2022 ), we only observed an increase in the number of cases, but no hospitalizations or deaths, which may have generated a sense of security and may have overlooked the suspected COVID-19 symptomatology ( Ascarza, 2022 ).

The present study indicated a higher probability of being vaccinated with the booster dose in people related to health sciences same results as Iran ( NeJhaddadgar et al., 2023 ), possibly explained by a better handling of information about vaccines ( Bartoš et al., 2022 ; Paterson et al., 2016 ), or by the higher risk of getting sick from COVID-19 ( Ing et al., 2020 ), however, studies in this population are variable; there are some that mention that health personnel are willing to be vaccinated with the booster dose, while other studies show that there is a group of people related to the health area who are reluctant or unwilling to accept a booster dose ( Lounis et al., 2022 ; Dzieciolowska et al., 2021 ; Verdú-Victoria et al., 2022 ). Our results are important in vaccination since it has been shown that a higher IBV with the booster dose in health personnel has been associated with a higher recommendation to their patients ( Paterson et al., 2016 ; Della Polla et al., 2022 ).

Third, it is important to note that the results of the survey show the sources of information to know about the COVID-19 booster dose. Our study also reports a high likelihood of IBV with the booster dose on the recommendation of health care professionals such as physicians, a result that is consistent with other research that evaluated the acceptability of COVID-19 vaccination on the recommendation of physicians and health care providers ( Herrera-Añazco et al., 2021a ; Folcarelli et al., 2022 ; Goldman et al., 2020 ; Reiter, Pennell & Katz, 2020 ). A systematic review mentions that the influence of physicians are the most important factors for the population to accept vaccination with the booster dose, because health personnel are best placed to disseminate standardized, evidence-based messages ( Lin, Tu & Beitsch, 2021 ). Additionally, a study conducted in China reported that 80.6% of its respondents reported that their physicians had an influence on them in making the decision to accept the vaccine ( Wang et al., 2020 ). Likewise, the Ipsos report that evaluated the 2022 trust ranking in urban population with internet access between May and June, indicated that doctors and scientists are the most trusted professionals for Peruvians ( Ipsos Perú, 2022 ). Therefore, it is very likely that the promotion of vaccination and IBV with the booster dose against COVID-19 falls mainly on health professionals. We also analyzed the recommendation of governmental health authorities such as MINSA, which is the entity in charge of directing health policies and actions in Peru ( Government of Peru, 2023 ), finding a higher probability of IBV with the recommendation of this agency; however, in the adjusted analysis it was not statistically significant. These findings are particularly important because government health authorities are key players in achieving optimal vaccination and adequate literacy ( Lazarus et al., 2021 ; Biasio, 2017 ). Several studies, including a survey that evaluated 19 countries in various regions of the world, indicate that people are more likely to be vaccinated if they trust their government authorities ( Folcarelli et al., 2022 ; Lazarus et al., 2021 ; Siegrist & Zingg, 2014 ; Lazarus et al., 2020 ). In this way, we can notice the great impact generated by physicians, who can influence the decisions of the population as well as their work as an indispensable entity in the prevention and promotion of health. Therefore, we recommend paying close attention to these results to use their influence on the diffusion of the vaccination not only against COVID-19, but even on other vaccines such as yellow fever, hepatitis B, or influenza ( Government of Peru, 2022 ).

The results of our study indicate a greater acceptance of IBV in the face of the recommendation of politicians. This finding is significant, as Herrera-Añazco et al. (2021a) said, the media usually give a lot of advertising space to politicians, which could be used to promote vaccination. In addition, a high influence of politicians on IBV has been reported in several studies ( Urrunaga-Pastor et al., 2021 ; Lazarus et al., 2021 ), however, this influence can be altered by several factors such as infodemic, doubts about vaccination, political instability, as well as the messages that politicians themselves post on their social networks ( Garcia et al., 2020 ; Borgesdo Nascimento et al., 2022 ; White et al., 2023 ; Malik et al., 2020 ). Therefore, it is suggested that politicians transmit information based on scientific evidence and promote vaccination campaigns adapted to the different realities of health access in each country.

No differences were found in IBV in people of rural and urban residence. It is possible that the difference between the percentage of respondents living in urban areas (87.3%) with respect to those living in rural areas (12.7%) did not allow a true comparison. However, other studies have reported that living in a rural area is associated with lower IBV, such as in Guatemala and marginalized communities in the United Kingdom and the United States, with access to vaccination sites and language being factors that negatively influenced vaccination progress and thus booster dose ( Taylor, 2022 ; Halvorsrud et al., 2022 ; Dong et al., 2022 ). Given that Peru is a country with a marked geographic variation, with many of its rural communities challenging access to health care ( Gozzer Infante, 2020 ) and limited access to information and communication technologies ( Calderón, 2022 ), a constant evaluation of vaccination in these sectors is recommended, especially in the departments of Huancavelica, Huánuco, Cajamarca, San Martín, Amazonas, Puno, Loreto, Madre de Dios, Ayacucho, Cusco, San Martín and Ucayali. As of February 12, 2023 they have the lowest vaccination coverage with the booster dose ( Ministry of Health of Peru, 2023a ).

Our research has certain limitations and there may be some biases, on the one hand, it is possible that there was a social desirability bias in the physical surveys, however, the staff tried to minimize this bias, ensuring their anonymity in each survey, having a friendly treatment with the person, asking in a neutral way when required or a little more indirectly when evaluating, for example, depressive symptoms. On the other hand, self-report bias, common in questionnaires of this type, could occur in virtual surveys; however, questions from validated questionnaires previously used in virtual surveys were used. As mentioned above, there were no statistically significant differences in the IBV between the physical and virtual surveys. Since we used non-random convenience sampling, it is likely that there was a selection bias that makes the results not extrapolated to the entire Peruvian population, so the results of the study should be taken with caution. In addition, there is a risk of representativeness in rural areas, since they represent only 12.8% of the respondents, as well as in age, since 86.5% of our sample was under 45 years of age. Although the number of people who entered the final analysis is known, it was not possible to quantify the response bias because it was an open invitation and we did not know how many people in total received the survey. On the other hand, the depressive symptoms subscale of the DASS-21 instrument has a sensitivity of 88.5% ( Román, Santibáñez & Vinet, 2016 ) and provides only a snapshot of recent mental health symptomatology, so depressive symptoms scores may not fully correlate with the clinical diagnosis made by a mental health professional. Additionally, the variables comorbidities and ESAVI were not adequately measured, as they were self-reported, likewise, COVID-19 suspicious symptomatology does not indicate disease, but symptoms compatible with the disease that were reported by the participant. Despite the limitations, this study establishes the association between sociodemographic variables and those related to the perception of the COVID-19 booster dose, which may contribute to the development of future strategies and improved immunization programs.