Vaccination is the most effective way to prevent diseases. Currently, immunization prevents 2 million to 3 million deaths per year, and, if vaccination coverage improves, another 1.5 million deaths could be avoided [1]. A decrease in vaccination represents a threat to the collective immunity acquired in recent years thanks to the efforts of health professionals [2].

The COVID-19 pandemic has drastically affected people and health systems worldwide. It has become a catalyst for many scientific advances, including the conception of a vaccine against COVID-19 [3]. This vaccine is considered one of the most important instruments to limit the spread or eliminate the pandemic, but its success is related to its acceptance worldwide [4-6].

According to the definition proposed by MacDonald and the SAGE Working Group on Vaccine Hesitancy [7], vaccine hesitancy is situated on a continuum from acceptance of all vaccines to total rejection. People who are hesitant about vaccination represent a heterogeneous group between these 2 extremes.

In 2019, the World Health Organization (WHO) rated vaccination hesitancy caused by antivaccine movements as one of the top 10 threats to global health [8] and warned of the dramatic growth of antivaccine theses and “fake news” in western Europe [9,10]. Vaccine hesitancy can be fueled by health information obtained from a variety of sources, including new media like the internet and social media platforms [2,4,11-13]. In particular, social networks have become a new paradigm for medical care, where power has passed from health professionals to patients and the legitimacy of science is questioned [2,14].

The antivaccine infodemic (misinformation and unfounded rumors about infection and vaccination) increased during the COVID-19 pandemic. It appeared on social networks long before the arrival of an effective vaccine, eroding confidence in vaccination among the community and making the job of health professionals difficult [4,10,11,15-17].

Globally, 63.1% of the adult population has received one dose of the COVID-19 vaccine, and 55.7% has received the complete regimen [18]. At the beginning of 2022, the Spanish Ministry of Health published that, in Spain, 80.5% of the total population and 90.4% of the population older than 12 years had been fully vaccinated against COVID-19 [19]. On the same dates, the Statistical Institute of Catalonia published that, in this region, 79.5% of the total population and 85.4% of the population over 12 years of age had been fully vaccinated against COVID-19 [20,21].

In this context, our study sought to assess the impact of the pandemic on the decision to get vaccinated against COVID-19, on the possible increase in doubts about vaccines in general, and on the decision to get vaccinated against other diseases. We also wanted to describe the potential influence exerted by gender and sociocultural characteristics.

The objective of our study was to evaluate the impact of the pandemic on public opinion about the decision to get vaccinated against COVID-19, doubts about routinely recommended vaccinations, and the final decision about vaccination. Also, we wanted to determine if sociodemographic and socioeconomic factors influenced decision-making about vaccination.

Of the surveyed population of residents of Catalonia aged at least 18 years in 2021, 90.8% showed a predisposition to get vaccinated against COVID-19, a lower percentage than that published in a serial survey conducted during the COSMO-Spain study promoted by the WHO (round December 9, 2021). According to the latter, 96% of the surveyed population stated they had received at least one dose of COVID-19 vaccine [23]. Similarly, in December 2021, the barometer of the Spanish Centre for Sociological Research showed that 96.5% of people surveyed had already been vaccinated against COVID-19, 3.2% had not, and 0.3% did not respond. Of the latter, 59.5% were not willing to be vaccinated, 4% had doubts, 3.1% would only do so under certain conditions, 21.7% would be vaccinated, and the rest did not respond [24]. Data from 2020 published by the Ministry of Health showed a primary vaccination coverage of 97% and a coverage for the 2 doses of the measles, mumps, and rubella (MMR) vaccine of 94.2% [25]. Finally, recent data showed coverage of the vaccine against COVID-19 of 90.4% and 85.4% of the population over 12 years of age in Spain and Catalonia, respectively [19,20]. This represented good vaccination coverage in Spain for both routinely recommended vaccines and the vaccine against COVID and exceeded the Spanish coverage for the 2020-2021 flu campaign, which was 67.7% for people older than 65 years of age and 72.0% for people older than 75 years of age [25].

In our study, 30.3% of people surveyed stated that, as a result of the COVID-19 pandemic, their doubts regarding recommended vaccinations had increased. Such doubts could imply a decrease in vaccination rates in general, such as the primary vaccination coverage, which is currently 97%. This effect could be mitigated by the evolution of the predisposition to vaccination during the pandemic. Indeed, the willingness of the Spanish population to get vaccinated against COVID-19 has been evolving with the progress of the vaccination campaign, as shown by the serial surveys carried out by the COSMO-Spain study. In this study, in the surveys prior to the start of the vaccination campaign, the percentage of people willing to get vaccinated against COVID-19 was 39% in November 2020. In the December 2021 survey, 96% of those surveyed reported having received some dose of the vaccine, and only 2% said they did not want to be vaccinated [23].

A study conducted in the United States during the pandemic also found that parental doubts about vaccinating children and the perception of risk about vaccines had increased. However, these doubts did not translate into less intention to administer routine vaccines to children [26]. This observation coincides with our results showing an increase in doubts about vaccination but an unchanged decision about vaccines by 87.0% of this population. However, 13.0% of the participants in the survey stated that, as a result of the COVID-19 pandemic, their decision on recommended vaccines had changed. This last group is related to antivaccination profiles, which could make it difficult for health professionals to maintain high vaccination coverage.

As for the sociodemographic variables, in contrast to other articles, we detected a greater predisposition to get vaccinated against COVID-19 or other vaccine-preventable diseases in women than in men [27,28]. Interestingly, as a result of the pandemic, women with children younger than 15 years of age were less likely to get vaccinated against COVID-19. Similarly, a review by Joshi et al [6] in 2021 showed that women and parents manifest less acceptance of the COVID-19 vaccine, which is why improving confidence in vaccines is recommended, especially in mothers. Other studies conducted with the UK and US populations indicated that women with young children are more concerned about vaccinating their children [28,29]. This could explain the high participation of women in our study, and we could deduce that, at certain socioeconomic levels, decision-making about the vaccination of children could be predominantly made by mothers. This observation is in agreement with data published by the Spanish Ministry of Health and Social Policy in 2009, showing greater maternal involvement in the care of other people in the family; moreover, in 2020, the European Commission ratified this situation [30,31]. In the same line, the dissemination through mommy blogs of the ideology of intensive motherhood, which is a cultural model of appropriate childrearing according to which mothers should unselfishly make a tremendous investment in their child, maintains the persistence of gender inequality and allows the dissemination of erroneous information about vaccines [32,33].

In agreement with other studies, we found a greater predisposition to get vaccinated and fewer doubts about vaccination as a result of the COVID-19 pandemic among older adults. Indeed, it is argued that older people are more likely to get vaccinated than younger people, since they are more concerned about their health and are more susceptible to getting sick [3,27,34,35].

Despite the high participation of people who had completed university studies, no relationship was found with attitudes for or against vaccination. Some studies have shown that the higher the level of education, the greater the acceptance of vaccines and the predisposition to prioritize vaccination [36-40]. On the contrary, there are also studies that found that sociodemographic levels do not influence the decision to vaccinate [41] or that a higher level of education coincides with greater doubts about vaccination [42].

Our study shows that cultural, religious, and family beliefs are associated with doubts and decision about vaccination, with a greater predisposition to get vaccinated against COVID-19 if the sociocultural environment is provaccine. These results support data published in previous studies [43,44].

We found that people who were not predisposed to get vaccinated against COVID-19 also stated that their doubts about vaccination increased as a result of the pandemic or reported having refused vaccines sometimes. This could indicate that there may be other factors, apart from sociodemographic and sociocultural factors, that can influence vaccine hesitancy: accessibility and cost, personal responsibility and risk perception, precautionary measures taken to vaccinate people, trust in health authorities and in vaccines, safety and efficacy of a new vaccine, and lack of information or misinformation about vaccines [3,6,44,45]. These factors cannot be interpreted either causally or independently of each other. It is much more plausible that several of the factors interrelate in a complex and dynamic way to influence individuals, confirming the WHO 3C Model (confidence, complacency, and convenience) of the factors influencing the decision to get vaccinated [3,46].

There is extensive literature showing that information from social networks can be a source of vaccine hesitancy; however, in this study, it was not possible to establish this association since only one-quarter of the respondents consulted social networks about COVID-19 vaccines [2,4,11-13]. This low level of searching on social networks could be explained by the results of other studies, such as the study by Hunt [47], which showed that people passively receive information from networks and are not aware of it [48], such as being a follower of mommy blogs and passively receiving erroneous information about vaccines [32]. However, we think that social networks provide an opportunity to directly communicate medical information to the public and that health systems should work on building disease detection and surveillance systems through the monitoring of social networks [49].

One of the limitations of this study is recruitment bias since people without access to the online survey could not participate. However, 97% of Catalan households have internet access, and 70.4% of Catalan internet were users of social networks in 2020 [50,51]. Another limitation is the impossibility of detecting if anyone repeated the survey; however, it was expected that few respondents would repeat it and therefore it would not influence the final result of the total sample. In the population surveyed, there was a predominance of women and people with a university education. This fact could result in not being fully representative of the Catalan population and could limit the interpretation and generalization of our study. The difficulty of reaching the antivaccine population using this survey was also known due to the difficulties in interacting with these groups. Therefore, to limit eventual bias deriving from this, in the sample size calculation, we considered that the proportion of antivaccine responses would be much lower than the provaccine responses.