CPHA Canvax

Addressing the Polarization of Vaccine Opinions

Marie-Eve Trottier, Noni E MacDonald, Lucie Bucci, Eve Dubé

Opposing viewpoints on the importance and benefits of vaccines are not new. However, the COVID-19 pandemic has exacerbated the divide between opposing opinions on vaccination, which has had an impact on public perceptions. We performed a literature review of more than 150 publications from different fields of research to understand how polarizing views on vaccination affect acceptance and uptake and contribute to the moral distress among health care professionals caring for patients opposed to vaccination. This CANVax in Brief will summarize the results of this literature review and identify some evidence-informed interventions that may help address this issue. 

Key concepts of polarizing opinions 

Vaccination is often a controversial topic that can divide families, friends, colleagues, and entire societies. Although vaccines are proven as effective public health interventions to control the spread, and reduce the burden, of diseases, there are skeptics in every society who believe that vaccinations are unsafe and unnecessary. Many studies to date have identified a range of concepts (e.g., political, societal) associated with the circulation of opposing or polarized views since the start of COVID-19 vaccination programs1 . Table 1 presents the key concepts and definitions associated with the polarization of opinions.

1. Polarization of opinion in public health and vaccination is a highly multidisciplinary research field. This is why we searched in political, sociological, health, and general science databases such as PubMed, Google Scholar, the PREV website (Réseau des praticiens canadiens pour la prévention de la radicalisation et de l’extrémisme violent), the World Health Organization database, the political science database of the Université de Montréal, and searched Google for other gray literature. We used key words such as: radicalization, polarization, extremism, COVID-19, politicization, climate change, anti-vaccination, misinformation, conspiracy theories, democracy, far right, medical populism, depolarization, misinformation economy, engagement, population science/climate change, post-truth era, declining trust in science, declining trust, populism and health, guidelines, counter misinformation, intervention to counter extremism, pre-debunking, debunking myths, opinions health, opinions vaccines, radicalization.

Table 1: Definitions of concepts linked to polarization of opinions on vaccines
Concepts Definitions
Echo chambers An environment in which a person encounters only beliefs or opinions that coincide with their own, so that their existing views are reinforced and alternative ideas are not considered(1).
Anti-establishment Against the establishment or established authority(1).
Far-right The extreme right wing of a political party or group(1).
Moral injury Psychological distress that results from a person having taken part in events that go against their moral beliefs or values.  For example, moral injury might have been experienced by frontline workers during the height of the COVID-19 pandemic when a lack of protective equipment, a perceived lack of support from employers or the public (e.g. picketing of vaccine opponents), and a high workload resulted in frontline workers’ inability to deliver the standard of care they were trained for, leading to feelings of guilt and shame. According to a study, in Canada, the moral injury rate associated with COVID-19 among healthcare workers was around 13%(2).
Misinformation Giving wrong information about something; the wrong information that is given(1).
Disinformation False information which is intended to mislead(1).
Backfire effect Also known as the “boomerang effect”, which happens when the correction of misinformation creates a reaction where opposite beliefs are reinforced and can predispose people to reject further similar information(3).
Key correlations of polarizing vaccine opinions 

Political ideology has been found to be a key link to polarized views on vaccines. According to the literature, people with apolitical beliefs or right-wing/conservative political beliefs are more likely to be opposed to vaccines than those who do not share their political beliefs(4,5). A study in the United States revealed that 16% of respondents who strongly identified with the Democratic Party had no intention of getting immunized against COVID-19 during the pandemic compared to 53% of those who strongly identified with the Republican Party (6). During the COVID-19 pandemic, governments around the world implemented measures to contain the virus that severely infringed on personal freedom, leading  to the rise of far-right organized movements, protesting violently against vaccine policies and other preventive measures(7). Policies, outcomes and reactions varied from country to country(8,9). Some governments were more coercive, while others achieved consensus with their populations.   

People whose beliefs are aligned with a more right-wing political party were found to be more skeptical towards scientific evidence (and even science deniers(10)) and more prone to align with “anti-establishment” values(4,7). Negative and uncertain feelings towards vaccines were also exacerbated due to a perceived lack of transparency and communication on the part of public health authorities. Government decisions were perceived as confusing because they changed accordingly to the publication of new data and the evolution of the pandemic and immunization strategies(11). This not only deflated trust in public health and government, but may have worsened polarization, especially during the implementation of mandatory vaccination policies (e.g., vaccination passports)(12).

Many studies also pointed to the role of social media in perpetuating vaccine polarization, especially the impact of the echo chamber effect(13). The echo chamber effect increases polarization because people are not in contact with different views about a topic, and their own opinions and views are reinforced by others with similar viewpoints. Echo chambers also align with human tendencies to seek information that confirms their pre-existing views, challenging social media campaigns that provide accurate information(3). Polarized viewpoints can also be very convincing to people with access to inaccurate, or not enough, information In some cases, especially on social media, opinions can shift entirely because of the convincing nature of some polarized views (e.g., personal stories) despite clear evidence to the contrary(14).

Consequences of opinion polarization on vaccines 

Consequences of opinion polarization are vast. Polarization can lead to division among communities, lead to negative health outcomes in populations, and erode democracy. It can also lead to extremism and violence(15). Vaccination polarization is often associated with mistrust in health authorities and lower adherence to public health measures(16). Through the spread of vaccine misinformation, polarized views can spread easily and quickly online, reaching large audiences. The expanded sharing of polarized views is associated with an increase in vaccine hesitancy and a decrease in vaccine uptake(17).

Polarized viewpoints can also negatively impact the ability of health care providers to provide optimal care. They face the risk of backlash from patients to whom they recommend vaccination. Dealing with angry and hostile patients has contributed to worsening working conditions for health care providers.  Emotional exhaustion, anxiety and work-related stress is contributing to feelings of inadequacy and moral injury(18). Hospitals and community health services have experienced patient surges and the possibility of other health crises arising threatens an already fragile health system where resignations among health care staff may become more common(19,20). A recent Canadian study conducted with critical care nurses found that 22% intended to quit(21).

Possible solutions to reduce opinion polarization on vaccines

Few evidence-based strategies to decrease opinion polarization were identified in our review. Most of the literature on this topic emphasizes the importance of preventing polarization through education, science literacy, and mitigating social exclusion to avert extremism and violence (refer to Table 2). A variety of approaches can be used to engage the public toward science, such as seeking out communication training, partnering with organizations, supporting post-secondary school to encourage students to study science communication, partnering with their institutions to broaden their reach, seeking out other scientists to learn strategies, and seeking information on how to communicate science to the public(22). Some studies have pointed out that to engage populations toward science, scientists engagement in communication is key(23). For instance, scientists should prioritize “informing the public about science, exciting the public about science, strengthening the public’s trust in science, tailoring messages about science, and defending science from misinformation”(24). 

The “public deficit models for mistrust in science” help us to understand many dimensions of the public’s lack of trust that could be worked on for better engagement : 1) deficit of knowledge, 2) deficit of trust (providing more information and being more transparent), 3) lack of understanding of the scientific process (explaining that science does not equal zero risk or that it does not deal in absolute certainties), 4) public deficit in understanding that science has no ethical or social responsibility for its application and its impacts (e.g., political decisions), 5) public deficit in understanding the benefits of science (e.g., knowledge about preventive measures during COVID-19 to avoid spreading the virus and several hospitalizations and deaths)(25) (Table 2). 

Table 2 : Dimensions to address with the public to maintain trust in science(25)
Deficit Areas Solutions
1) Public deficit in understanding scientific knowledge Upgrade knowledge with education
2) Public deficit in trust in science Give more information, and more nuanced information, and be more transparent.
3) Public deficit in understanding scientific process  Explain that science does not mean zero risk for vaccination, and that there are some uncertainties. 
4) Public deficit in understanding that science has no ethical or social responsibility for its application or impacts Other instances, such as governments, will implement information given by science, based on their ideology. Political decisions are not science. 
5) Public deficit in knowledge in the benefits of science Explain the motives behind science and discuss the benefits from science. 


Addressing online misinformation and disinformation about vaccination with debunking and pre-bunking strategies could help to prevent polarization, but so far, results of the efficacy of debunking and pre-bunking remain uncertain(26). Once polarization exists, communication strategies such as motivational interviewing (which aims to inform people about vaccinations according to specific needs and levels of knowledge, with respectful acceptance of beliefs between care workers and patients), can help to restore trust and reduce extreme views(25,27). On a broad level, drawing on lessons learned from climate change, coordination between scientists, journalists, advocacy groups, and political leaders appears to be essential to shift the public toward a common goal(28). Framing normative messages across ideological spectrums can be effective (e.g., messages linked to partisan values and beliefs). For example, if the economy is an important value for more conservative people, messages can highlight the societal costs of non-vaccination. Diversifying messengers by choosing people from different political affiliations or scientific/academic backgrounds, and avoiding ostracizing others in communication interventions, are also key.

In conclusion, opinion polarization about vaccination can have dramatic consequences, leading to vaccine refusal, disease outbreaks, suffering, and death among populations, in addition to moral injury among health care professionals. Although it is not possible to eliminate polarization, better collaboration between scientific experts, government, and media can play a major role in preventing or mitigating the polarization of opinions. 


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