Conspiracy theories are traditionally thought to drive vaccination hesitancy, leading public health campaigns to focus on debunking these myths to increase vaccination uptake. However, recent research published in Social Psychological and Personality Science suggests a more complex interaction.
While conspiracy beliefs about COVID-19 can indeed exacerbate hesitancy toward vaccination, the study provides stronger evidence that vaccination hesitancy itself can lead to an increase in conspiracy beliefs, suggesting a rationalization process that evolved as the pandemic progressed.
“Vaccination is one of the great achievements of science that has enabled humanity to minimize the number of casualties of lethal diseases,” said study author Jan-Willem van Prooijen, an endowed professor of radicalization, extremism, and conspiracy thinking at Maastricht University.
“Yet, many citizens are hesitant to get vaccinated, and this is heavily correlated with conspiracy beliefs. When the worldwide 2021 COVID-19 vaccination campaign took place, there were also a lot of conspiracy theories about the vaccine. I wondered how the relationship between vaccination hesitancy and conspiracy beliefs would unfold over time during this event.”
Previous research has consistently found a correlation between conspiracy theories and reluctance to vaccinate. However, these studies mainly used cross-sectional methods (analyzing data from a single point in time) and left a critical question unresolved: Do conspiracy beliefs lead to vaccine hesitancy, or do individuals use conspiracy theories to rationalize an existing hesitancy?
Van Prooijen and his colleagues aimed to clarify these temporal dynamics using a more robust longitudinal approach. The research was conducted in two separate studies: one in the Netherlands and the other in the United States. The Dutch study was structured around three survey waves spanning from February to July 2021. The initial wave in February started with a large sample of 4,558 participants.
In each wave, participants were first asked whether they had already received a COVID-19 vaccine. Those who had not were then asked about their intention to vaccinate on a scale from 1 (certainly not) to 5 (certainly will). Additionally, the surveys measured COVID-19 conspiracy beliefs through a series of items, which probed beliefs such as the virus being a hoax or financially motivated by interest groups.
The methodology in the U.S. mirrored that of the Dutch study but was condensed into two waves (March and April 2021) and involved a smaller initial sample of 602 participants.
In the Dutch study, the researchers found that participants who initially held stronger conspiracy beliefs were likely to show a decrease in vaccination intentions over time. This supports the hypothesis that conspiracy beliefs can erode trust in medical advice and discourage individuals from getting vaccinated.
On the other hand, the analysis also revealed that Dutch participants with lower vaccination intentions at the outset were more likely to embrace conspiracy theories as time went on. This suggests a rationalization process where individuals who are hesitant to vaccinate find and adopt conspiracy theories that justify their reluctance.
“Conspiracy beliefs are correlated with vaccination hesitancy, often leading to the conclusion that conspiracy beliefs decrease people’s willingness to get vaccinated,” van Prooijen told PsyPost. “But correlation is not causation: An alternative possibility is that people use conspiracy theories to rationalize their existing vaccination hesitancy. Our findings provide some support for both ideas (that conspiracy theories shape, or help rationalize, an unwillingness to get vaccinated), but they more consistently support the ‘rationalizing’ idea.”
Interestingly, the findings from the United States diverged somewhat from those observed in the Netherlands. In the U.S. study, the researchers found that participants with lower initial intentions to vaccinate were more likely to endorse stronger conspiracy beliefs in the subsequent wave. However, initial conspiracy beliefs did not significantly predict a decrease in vaccination intentions by the second wave.
“I was surprised that the support for the rationalizing hypothesis (i.e., vaccination hesitancy predicts more conspiracy beliefs over time) was more consistent than for the idea that conspiracy theories shape vaccination hesitancy (i.e., conspiracy beliefs predict more vaccination hesitancy over time),” van Prooijen said.
The researchers controlled for various factors such as age, gender, education, and political ideology, which could influence the outcomes. But like all research, the study has limitations to consider.
“Longitudinal approaches such as in the current study help establish how the relationship between two variables (in this case, conspiracy beliefs and vaccination hesitancy) unfolds over time, but still are not ideal to establish causality,” van Prooijen explained. “Particularly the idea that vaccination hesitancy increases conspiracy beliefs needs to be tested experimentally.”
Future research could explore how these dynamics play out in different cultural or political contexts and whether these patterns hold for other vaccines and public health measures. Further investigation is also needed to understand the underlying psychological processes through which people use conspiracy theories to rationalize their health-related decisions.
“In general, my long-term goal in my research is to establish the role that conspiracy beliefs play in public health, radicalization, and well-being,” van Prooijen said. “The present research was specifically about the COVID-19 vaccines and took place during the 2021 vaccination campaign. But I think it is important to look at the implications of conspiracy theories for people’s attitudes towards medical science, health professionals, and medical interventions more broadly.”
“In many countries dangerous childhood diseases are resurfacing (e.g., the measles). In my country – the Netherlands – recently several babies have died of whooping cough, which appeared due to a decreased willingness of parents to get their children vaccinated. It is quite plausible that conspiracy theories have contributed to this.”
The study, “Do Conspiracy Theories Shape or Rationalize Vaccination Hesitancy Over Time?“, was authored by Jan-Willem van Prooijen and Nienke Böhm.