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Introduction
Previous studies have demonstrated the negative impacts of misinformation related to Covid-19 and dengue on general population beliefs (e.g., vaccine trust: Allington et al., 2023; Del Riccio et al., 2021; Gagnon-Dufresne et al., 2023) and behaviors (e.g., vaccine hesitancy: Allington et al., 2023; Gagnon-Dufresne et al., 2023; Roozenbeek et al., 2020). Consequently, the spread of health-related misinformation has been recognized as a critical global health challenge, often referred to as an "infodemic" (World Health Organization, 2024; Ricaurte, 2021) . This phenomenon is prevalent in Brazil, with several studies indicating a high prevalence of health-related misinformation spread by both the public and health authorities/professionals during the Covid-19 pandemic (Martins-Filho et al., 2022; Paumgartten et al., 2020; Salvador et al., 2023; Silva et al., 2023).
Moreover, it is well-established that some sociodemographic (e.g. , political views, age, income, education) and health-related outcomes (e.g. , number of vaccine doses received, intentions to receive or administer vaccines to their children) are associated with susceptibility to Covid-19 misinformation (Del Riccio et al., 2021; Ramos et al., 2022; Roozenbeek et al., 2020; Salvador et al., 2023). However, while the impact of multiple factors on belief in Covid-19 misinformation has been extensively studied, research addressing misinformation about arboviruses, particularly dengue, remains scarce (Carey et al. , 2020; Nan et al. ,2022) . A recent systematic review identified only one Brazilian study addressing misinformation about Zika and yellow fever (Nan et al. , 2022). This gap is concerning given Brazil's history of dengue outbreaks and epidemics (Xavier et al., 2017), including the current record-breaking outbreak in Rio de Janeiro (Secretaria Estadual de Saúde do Rio de Janeiro [SES-RJ], 2024), which may be exacerbated by beliefs in misinformation about false prevention and treatment measures (e.g., use of vinegar and ivermectin - Estadão, 2024; Ministério da Saúde [MS], 2024; Uol, 2024).
Previous research has suggested potential connections between Covid-19 and dengue outbreaks, with lockdowns and social distancing possibly contributing to increased dengue cases in several Asian countries due to reduced prevention efforts and misdiagnosis because of the similarity of symptoms (Wiyono et al., 2021). Nevertheless, to our knowledge, no studies have directly investigated the possible similarities or differences between reasons to believe, sociodemographic, and health-related outcomes of individuals who believe in misinformation about dengue and Covid-19 in Brazil. Given the ongoing dengue epidemic in Rio de Janeiro and the dissemination of health-related misinformation, this study aims to: 1) compare levels of belief in misinformation about Covid-19 and dengue; 2) investigate associations between sociodemographic factors, health-related outcomes, and beliefs in misinformation; 3) explore the reasons underlying these beliefs among residents of Rio de Janeiro State (RJ).
Method
Design and sample
A cross-sectional online opinion study, using the Qualtrics platform to retrieve quantitative and qualitative, and a 20-minute questionnaire, was conducted in February 2024. This study was conducted by researchers from the Federal Fluminense University, with funds from the Rio de Janeiro State government. Participants were recruited only in the Rio de Janeiro State through snowball sampling technique (i.e. , via dissemination in WhatsApp groups of the researchers' network) and boosting publications with information about our research on Facebook. The only target used during boosts was the location (i.e. , Rio de Janeiro state). The initial sample was 196 adults, 16 cases were removed because participants answered only the sociodemographic or health-related questions (i.e. , independent variables). The final analytic sample comprised 180 adults who answered at least one of the misinformation questions (i.e., dependent variables). This study followed the Brazilian National Health Council guideline 510/2016, which dispenses the submission and registration of public opinion surveys to ethics committees.
Variables and research questionnaire descriptions
All variables assessed were collected with an ad hoc questionnaire divided into two parts: 1) sociodemographic and health-related outcomes; and 2) misinformation outcomes. The survey questionnaire used skip logic to improve the participant experience. For example, if the participant answered that he/she does not search for health information on social media, the question about which social media was most used to consult such information was not displayed. Consequently, variations in response rates across questions should be interpreted cautiously, as they reflect sub-sample differences rather than missing data.
Sociodemographic and health-related variables (independent variables)
The first part of the questionnaire employed a structured format to collect data on sociodemographic and health-related variables. These included age, family income, religious belief level, number of Covid-19 vaccine doses received by the participant, and number of doses given to their children (continuous variables); gender (1 = Male; 2 = Female), education level (1 = Elementary school; 5 = Postgraduate), political view (left-wing, center, right-wing, no political preference), search for health information in social media, most used social media for health information (YouTube, Facebook, Instagram, Twitter/X, WhatsApp, Telegram, TikTok, Kwai), have children under 18 years old, intends to receive new Covid-19 and dengue vaccines, intends to vaccinate child with new Covid-19 and dengue vaccines (0 = No; 1 = Yes). To account for potential biases, two additional dichotomous questions were included at the end of the online survey. Participants were asked whether they consulted external sources (e.g., Google) to answer the questions related to misinformation. Participants were also asked to indicate if they were health professionals.
Misinformation outcomes (dependent variables)
Following the assessment of sociodemographic and health-related outcomes, participants assess the veracity (0 = False; 1 = True) of six statements about Covid-19 and dengue (table 1). These statements were derived from mainstream media and Brazilian government anti-misinformation campaigns (#Brasilcontrafake). Subsequently, participants were asked to justify their belief or disbelief in each statement. A predefined list of potential reasons was provided (e.g., Perceived vaccine reliability, and information from healthcare professionals -HCPs), allowing participants to select more than one option. An 'other' category was also available for specifying alternative justifications.
Table 1 Misinformation rated as false or true by the participants
Note. 1All the statements were false; GMO = Genetically modified organisms.
Source: own elaboration.
Data analysis
Binary logistic regression was used for ordinal independent variables, given the dichotomous nature of the dependent variables. Chi-squared or Fisher's exact test (when expected count < 5 in one of the response categories) was employed for categorical independent variables (Tabachnick et al., 2013). To assess multi-collinearity between independent variables, variance inflation factor (VIF) values were calculated, with results indicating low collinearity (VIF < 4; Kim et al., 2019). The pairwise deletion was applied to handle missing data in Chi-square and Fisher's exact tests, while listwise deletion was used for logistic regression. All quantitative analyses were performed using SPSS version 26 and the software JASP version 0.17.2.1.
Qualitative data on reasons for belief or disbelief in misinformation were analyzed using Bardin's content analysis (1977/2016). Data were organized and synthesized based on thematic similarities and wording, adhering to Bardin's criteria of mutual exclusivity, homogeneity, and pertinence. Analyses were performed using MS Excel and SPSS version 26.
Results
Sample characteristics
The mean age of the sample was 56.65 (SD = 12.99), and most are Female (66.45%). The mean family monthly income was R$ 9.963,64 (SD = 7.680,71), which is equivalent to $ 1.992.73 (SD = 1.536.14)1. Most participants did not have children (64.43%), were attending, or had already completed an undergraduate degree (35.6%), followed by individuals with postgraduate degrees (32.2%) and high school diplomas (28.1%). The sample leaned left politically (45.2%), with a quarter (26.03%) reporting no political preference and 21.92% identifying as right-wing. Approximately half (48.9%) of participants sought health information related to Covid-19 and dengue on social media, primarily YouTube (41.4%), followed by Facebook (33.33%) and Instagram (12.64%).
Participants reported receiving a mean of 3.55 Covid-19 vaccine doses (SD = 1.5). Vaccine acceptance for future Covid-19 and dengue vaccinations was high, with 65.7% and 80% of participants expressing interest, respectively. A mean of 2.33 Covid-19 vaccine doses (SD = .96) was reported for participants' children, and 71% and 86.5% of participants intended to vaccinate their children against Covid-19 and dengue, respectively. These findings suggest a potentially higher confidence in the safety and efficacy of the dengue vaccine compared to the Covid-19 vaccine. They may also indicate more concern about dengue than Covid-19.
To mitigate potential biases, we assessed participant reliance on external information sources and healthcare professional status. Results indicated that 92.62% of participants did not consult any external information (e.g., google) while answering our questionnaire, and 85.81% were not health professionals. Detailed descriptive statistics for sociodemographic, health-related, and misinformation outcomes are presented in table 2.
Table 2 Descriptive statistics for sociodemographic, health-related, and misinformation outcomes
| Variable type | Variables | Groups | N (%) | Mean (SD) | Min- Max |
|---|---|---|---|---|---|
| IV | Age | 180 | 56.65 (12.99) | 18-80 | |
| Family income (R$) | 179 | 9967,64 (768O,71) | 0-30.000 | ||
| Religious belief level | 146 | 1.38 (.87) | 0-3 | ||
| Vaccine doses N° | 149 | 3.55 (1.5) | 0-6 | ||
| Child vaccine doses N° | 52 | 2.33 (.96) | 0-3 | ||
| Gender | Male Female | 51 (33.55) 101 (66.45) | |||
| Education | Elementary school High school Undergraduate Postgraduate | 6 (4.02) 42 (28.18) 57 (35.57) 48 (32.21) | |||
| Political view | Left-wing Center Right-wing No political preference | 66 (45.2O) 1O (6.85) 32 (21.92) 38 (26.O3) | |||
| Have child (< E8 years) | Yes No | 53 (35.57) 96 (64.43) | |||
| Health Info. in social media | Yes No | 88 (48.89) 92 (51.11) | |||
| Most used social media for health info | YouTube Facebook Instagram Twitter (X) WhatsApp | 76 (41.78) 29 (33.33) 11 (12.64) 7 (8.04) 4 (4.6) | |||
| Intends to receive new Covid-E9 vaccines | Yes No | 98 (65.77) 51 (34.23) | |||
| Intends to receive dengue vaccine | Yes No | 119 (79.87) 3O (16.67) | |||
| Intends to vaccinate child with new Covid-E9 vaccine dose | Yes No | 37 (71.15) 15 (28.85) | |||
| Intends to vaccinate child for dengue* | Yes No | 45 (86.54) 7 (13.46) | |||
| Information search during survey | Yes No | 11 (7.78) 138 (92.62) | |||
| Health professional | Yes No | 21 (14.19) 127 (85.81) | |||
| DV | Covid-E9 super virus | False True | 142 (8O.27) 35 (19.77) | ||
| Covid-E9 vaccine side- effects in children | False True | 113 (67.26) 55 (32.74) | |||
| Ivermectin for Covid-E9 prevention and treatment | False True | 118 (71.95) 46 (28.O5) | |||
| Dengue GMO (mosquito) | False True | 135 (85.99) 22 (E4.01) | |||
| Dengue Vinegar | False True | 113 (75.33) 37 (24.67) | |||
| Ivermectin for dengue prevention and treatment | False True | 139 (97.29) 10 (6.71) | |||
Note. *During this study, Rio de Janeiro had not started dengue vaccination; DV = Dependent variable; GMO = Genetically modified organisms IV = Independent variable; R$ = Brazilian real; SD = Standard deviation.
Source: own elaboration.
Difference in levels of belief in misinformation about Covid-19 and dengue
Participants exhibited higher levels of belief in Covid-19 misinformation (M = 26.85%) compared to dengue misinformation (M = 15.1%). This difference is more noticeable between the misinformation about ivermectin as prevention/treatment, with 28.05% endorsing the misinformation about Covid-19 versus 6.7% for dengue. Furthermore, a significant proportion of the participants believed in the Covid-19 children's vaccine side effects (32.74%), and in the Covid-19 supervirus (19.77%) misinformation. Regarding dengue, 24.67% believed the misinformation about genetically modified mosquitoes (GMO) contributing to Zika virus outbreaks during an attempt to combat dengue, while 14.01% believed in vinegar as a dengue prevention strategy.
Associations between sociodemographic, health-related outcomes and beliefs in misinformation
Logistic regressions were performed to assess whether ordinal variables (i.e. age, income, education, religious beliefs, number of Covid-19 vaccine doses received and administered to children) were predictors of belief in misinformation about Covid-19 and dengue. However, model fit information and omnibus test demonstrate that our regression models for the Covid-19 supervirus, vinegar, and ivermectin for dengue prevention misinformation are no better than a null model (p > .05). Therefore, these dependent variables were not further explored in regression results. The findings of the logistic regressions for the remaining dependent variables are presented in table 3.
Table 3 Logistic regression models for predicting belief in misinformation about Covid-19 and dengue between Rio de Janeiro citizens
| Predictors | Covid-19 vaccine side-effects in children1 | Ivermectin for Covid-19 prevention/ treatment2 | Dengue GMO (mosquito)2 |
|---|---|---|---|
| OR (95% CI) | OR (95% CI) | OR (95% CI) | |
| Vaccine doses N° | 3.77 (1.31, 10.81)* | .27 (.09, .78)* | .21 (.05, .86)* |
| Child vaccine doses N° | 2.42 (.72, 8.10) | .73 (.21, 2.44) | 2.11 (.37, 11.95) |
| Age | .95 (.87, 1.04) | 1.06 (.96, 1.16) | 1.10 (.97, 1.25) |
| Religious belief level | .83 (.28, 2.48) | .82 (.26, 2.59) | 1.44 (.41, 5.02) |
| Family income (R$) | 1.00 (1.00, 1.00) | 1.00 (1.00, 1.00) | 1.00 (1.00, 1.00) |
| Education | 1.84 (.57, 5.93) | .40 (.11, 1.47) | .19 (.02, 1.47) |
Note. OR odds ratio; CI confidence interval;* p < .02; 1 The category "False" is the reference; 2 The category "True" is the reference.
Source: own elaboration.
Logistic regression analyses revealed that for each unit increase in the number of received Covid-19 vaccine doses, there are greater 277% times the odds of the individual not believing the misinformation about Covid-19 vaccine side-effects in children (OR 3.77, 95% CI 1.31, 10.81). Similarly, the odds of endorsing misinformation about ivermectin for Covid -19 prevention/treatment decreased by 73% (OR .27, 95% CI .09, .78), and dengue misinformation related to GMO by 79% (OR .21, 95% CI .05, .86) for each additional vaccine dose. No significant differences were found between other sociodemographic or health-related variables and misinformation beliefs.
To examine associations between categorical variables and misinformation beliefs, chi-square or Fisher's exact tests were employed. Significant associations were found between political views and beliefs in the misinformation regarding COVID-19 supervirus, vaccine side effects in children, ivermectin as Covid-19 prevention/treatment, dengue GMO (p < .001), and ivermectin as dengue prevention/treatment (p = .003). Right-wing individuals exhibited a moderate to strong propensity to endorse misinformation claims about COVID-19 supervirus (ф = .47), dengue GMO (ф = .34), ivermectin as dengue prevention/ treatment (ф = .30), COVID-19 children vaccine side-effects (ф = .73), and ivermectin as COVID-19 prevention/treatment misinformation (ф = .67). There was no significant association between political view and beliefs in the vinegar for dengue prevention (table S1).
Significant associations were also found between search health information in social media and belief in the misinformation regarding Covid-19 supervirus (p = .002), vaccine side effects in children (p < .001), and ivermectin as Covid-19 prevention/treatment (p =.003). Individuals who search for health information on social media were slightly (ф = .23 to .29) more inclined to believe in all Covid-19 misinformation. On the other hand, there was no significant association between search health information in social media and beliefs in any dengue misinformation (table S2).
Furthermore, there were significant associations between intent to receive new Covid-19 vaccines and belief in the misinformation regarding Covid-19 supervirus, vaccine side effects in children, dengue GMO, ivermectin for Covid-19 and dengue prevention/treatment (p < .001). Individuals who do not intend to receive new COVID-19 vaccines were strongly more inclined to believe in all Covid-19 misinformation (ф = .52 to .77) and moderately more inclined to believe in dengue GMO (ф = .33), and ivermectin as dengue prevention/treatment (ф = .31). No significant association was found between intention to receive new Covid-19 vaccines and belief in vinegar as dengue prevention strategy (table S3).
Similarly, there were significant associations between the intent to receive dengue vaccine and belief in the misinformation regarding Covid-19 supervirus, vaccine side effects in children, dengue GMO, ivermectin as Covid-19 prevention/treatment strategy (p < .001), and dengue prevention/treatment (p = .01). Individuals expressing hesitancy towards dengue vaccination exhibited a stronger propensity to believe in all Covid-19 misinformation (ф = .55 to .59), and slightly more inclined to believe in dengue GMO (ф = .29), and ivermectin as dengue prevention/treatment misinformation (ф = .24). No significant association was found between dengue vaccination intent and belief in the vinegar as dengue prevention strategy (table S4).
Significant associations also emerged between having a child and belief in the misinformation regarding Covid-19 supervirus (p = .022), with individuals who had no children under 18 years old exhibiting a slightly higher likelihood of endorsement (ф = .19). There were no significant associations between have child and beliefs in any other misinformation (table S5). On the other hand, significant associations were observed between intention to vaccinate a child with new Covid-19 vaccines and belief in the misinformation regarding Covid-19 vaccine side effects in children (p < .001), dengue GMO (p = .04), ivermectin for Covid-19 (p < .001) and dengue prevention/treatment (p = .02). Individuals who do not intend to vaccinate their child with new Covid-19 vaccines were strongly more inclined to believe in Covid-19 vaccine side effects in children (ф = .86), ivermectin as Covid-19 prevention/treatment misinformation (ф = .56), and moderately more inclined to believe in dengue GMO (ф = .31) and ivermectin as dengue prevention/treatment (ф = .37). Conversely, no significant associations were found between intention to vaccinate child with new Covid-19 vaccines, and beliefs in Covid-19 supervirus, or vinegar as dengue prevention strategy (table S6).
Similarly, there were significant associations between intention to vaccinate children for dengue and belief in the misinformation regarding Covid-19 supervirus (p = .006), vaccine side effects in children, and ivermectin for Covid-19 prevention/treatment (p < .001). Individuals who do not intend to vaccinate their child were strongly more inclined to believe in all Covid-19 misinformation (ф = .52 to .59). However, in contrast with the findings related to the intention to vaccinate the child with new doses of Covid-19, no associations were identified between intention to vaccinate child for dengue and belief in any dengue misinformation (table S7).
Regarding possible differences between healthcare professionals and the overall Rio de Janeiro population, we found that healthcare professionals exhibited a slightly lower likelihood of believing in ivermectin as Covid-19 prevention/ treatment (p = .047, ф = .16). No significant associations were found between being a healthcare professional and beliefs in any other misinformation (table S8), or between misinformation beliefs and social media usage (table S9), gender (table S10), information search behavior during the survey (table S11).
Reasons to believe or disbelieve misinformation
Overall, our quantitative findings indicated higher levels of belief in Covid-19 misinformation compared to dengue misinformation. These disparities were also corroborated by our qualitative data, with participants providing more reasons to justify beliefs in Covid-19 misinformation (e.g., "I don't trust Covid vaccines, I have full confidence in other vaccines").
A minimum of 150 participants provided responses to questions regarding reasons for believing or disbelieving misinformation. To enhance data manageability and analysis, only reasons endorsed by at least 5% (n ≥ 7) of participants were included in subsequent analyses. The main reasons are listed in table 4. Most reasons were displayed as an answer option to the questions "why you believe that this information is true/false?" during the survey. Only the reasons beginning with "other:" were formulated based on a synthesis of the comments (Bardin content analysis) provided by participants in the "other, which?" answer option.
Table 4 Descriptive statistics for reasons to believe or disbelieve misinformation
| Misinformation | Reasons why believe1 | N° | Reasons why don't believe1 | N° |
|---|---|---|---|---|
| Covid-19 supervirus | Belief that vaccines are not reliable | 13* | Belief that vaccines are reliable | 94* |
| Health professionals said it was true | 10 | See the information in mainstream media | 15 | |
| - | - | Health professionals said it was false | 22 | |
| - | - | Other 1: previous knowledge/ beliefs | 17 | |
| Covid-19 vaccine side-effects in children | See the information in social media | 9 | Belief that vaccines are reliable | 68* |
| The belief that vaccines are not reliable | 11 | See the information in mainstream media | 11 | |
| See the information in mainstream media | 10 | Health professionals said it was false | 34 | |
| Health professionals said it was true | 25* | Other 1: previous knowledge/ beliefs | 18 | |
| Ivermectin for Covid-19 prevention and treatment | Used as prevention and had no Covid-19 | 20* | See the information in social media | 16 |
| Health professionals said it was true | 15 | See the information in mainstream media | 40 | |
| Used as a treatment and got better | 12 | Health professionals said it was false | 69* | |
| See the information in social media | 7 | Other 1: previous knowledge/ beliefs | 10 | |
| Family or peers believe in the information | 7 | Family or peers believe in the information | 7 | |
| Dengue GMO (MOSQUITO) | See the information in mainstream media | 8* | See the information in social media | 10 |
| - | See the information in mainstream media | 34 | ||
| - | Health professionals said it was false | 50* | ||
| - | - | Other 1: previous knowledge/ beliefs | 23 | |
| - | - | Other 2: never saw the information | 12 | |
| Dengue Vinegar | See the information in social media | 9 | See the information in social media | 10 |
| See the information in mainstream media | 10* | Health professionals said it was false | 39* | |
| Family or peers believe in the information | 7 | See the information in mainstream media | 28 | |
| - | Family or peers believe in the information | 7 | ||
| - | Other 1: previous knowledge/ beliefs | 17 | ||
| - | Other 2: never saw the information | 11 | ||
| Ivermectin for dengue prevention and treatment | - | See the information in social media | 11 | |
| - | See the information in mainstream media | 40 | ||
| - | Health professionals said it was false | 63* | ||
| - | Other 1: previous knowledge/ beliefs | 14 | ||
| - | Other 2: never saw the information | 10 |
Note. 'Participants could provide more than one reason why they believed (or not) in the misinformation, but the same participant could not provide both reasons to believe and disbelieve; *Most reported.
Source: own elaboration.
The main reasons for believing misinformation about Covid-19 were: 1) listening to health professionals who reinforce misinformation; 2) using ivermectin as prevention and not having contracted Covid-19; and 3) belief that vaccines are unreliable. Similarly, the main reasons for not believing in the Covid-19 misinformation were: 1) Perceived vaccine reliability; and 2) listen to health professionals who refute misinformation. Other reasons for not believing the misinformation related to Covid-19 supervirus, vaccine side effects, and ivermectin for prevention/treatment were related to: 1) previous knowledge/beliefs (e.g. , "ivermectin is a dewormer, not an antiviral"; "Covid-19 is a virus, basic biology"; "vaccines don't create super viruses"; "many countries already vaccinate children").
Regarding dengue, the main reason for believing the misinformation was: 1) seeing the information being disseminated in mainstream media. No reasons were listed for the misinformation related to the ivermectin use, as only 10 participants believed this information and provided different reasons for their belief. On the other hand, the main reason for not believing in the dengue misinformation was to listen to health professionals who refute misinformation. Other reasons for not believing the misinformation related to dengue GMO, vinegar, and ivermectin as dengue prevention/intervention strategy was related to: 1) previous knowledge/beliefs (e.g., "these mosquitoes were bred and monitored by Fiocruz"; vinegar does not kill larvae"; "ivermectin does not kill virus"); and 2) never saw the information (e.g., "I haven't seen this news"; "I've never heard of this happening").
Discussion
The main aim of this paper was to compare belief levels in Covid-19 and dengue misinformation in a sample from the RJ. Our primary finding indicates that participants exhibited greater belief in Covid-19 misinformation compared to dengue misinformation. Specifically, misinformation concerning Covid-19 vaccine side effects in children and dengue GMOs was perceived as accurate by a substantial proportion of the sample. Conversely, few individuals endorsed misinformation about vinegar and ivermectin as dengue prevention or intervention strategies. This discrepancy is noteworthy, particularly given the higher prevalence of beliefs in ivermectin's efficacy against Covid-19 (28.05%) relative to dengue (6.7%). The observed disparity in misinformation beliefs between Covid-19 and dengue might be attributed to several factors.
For instance, the Brazilian government's denialist stance during the pandemic (Carvalho et al., 2022; Martins-Filho & Barberia, 2022; Silva et al., 2023; Souto et al. , 2024), alongside with recommendations regarding the use of ivermectin as part of a so-called "early treatment for Covid-19" (Hentschke-Lopes et al., 2022; Silva et al. , 2023), likely contributed to the proliferation of ivermectin-related beliefs. Additionally, the promotion of ivermectin use and anti-vaccination campaigns by healthcare professionals during Covid-19 pandemic (Hentschke-Lopes et al., 2022; Silva et al., 2023; Paumgartten & Oliveira, 2020), as well as the widespread circulation of Covid-19-related fake news on mainstream and social media platforms (Carvalho et al. , 2022; Souto et al. , 2024), likely exacerbated the spread of misinformation. However, given the concurrent circulation of dengue-related misinformation about ivermectin and vinegar on Brazilian media platforms (MS, 2024; Estadão, 2024; Uol, 2024), the observed discrepancy does not appear consistent with a recency effect. (i.e., a cognitive bias that favors recent events over historical ones; a memory bias - Wyler & Oswald, 2016). If this were the case, a higher prevalence of dengue misinformation would be expected, especially considering the severity of the dengue epidemic in RJ during this study period (SES-RJ, 2024).
The proposed explanations are supported by the indings related to the reasons for believing and disbelieving misinformation, as well as the associations between sociodemographic factors, health outcomes, and misinformation beliefs. Perceived vaccine reliability and information received from healthcare professionals emerged as primary determinants of both beliefs and disbeliefs in Covid-19 misinformation. These findings align with previous national and international research linking trust in science, vaccines, and healthcare institutions to vaccination uptake (Carvalho et al., 2022; Del Riccio et al., 2021; Roozenbeek et al. , 2020; Salvador et al. , 2023; Souto et al. , 2024; Oliveira et al., 2024). Conversely, reliance on mainstream media as a source of information was associated with belief in dengue misinformation, while trust in healthcare professionals remained a key factor in disbelief. These results corroborate prior research on Covid-19 and dengue, highlighting the critical role of both traditional and social media in both the dissemination and correction of misinformation during public health crises (Lwin et al., 2021; Oliveira et al., 2024; Gagnon-Dufresne et al. , 2023).
Furthermore, our indings reveal that for each unit increase in the score for Covid-19 vaccine doses number, there is greater 277% times the odds of the individual not believing the misinformation about Covid-19 vaccine side-effects in children, less than 73% and 79% odds of the individual believe in the misinformation about ivermectin for Covid-19 prevention/treatment, and the misinformation about dengue GMO respectively. Moreover, individuals with no intention to receive or administer the Covid-19 vaccine to their children exhibited significantly higher belief in all Covid-19 misinformation and slightly to moderate belief in dengue GMO and ivermectin misinformation. Similar patterns were observed for dengue vaccination intentions with strong associations between unwillingness to vaccinate children for dengue and belief in Covid-19 misinformation. These findings aligned with previous national and international research demonstrating that belief in misinformation related to Covid-19 reduces the intention to get vaccinated and to vaccinate their children (Carvalho et al., 2022; Del Riccio et al., 2021; Roozenbeek et al., 2020; Salvador et al., 2023; Souto et al., 2024; Oliveira et al., 2024), as well as increase the willing to use ivermectin (Van Scoy et al., 2023; Silva et al., 2023). This is especially true in Brazil, with some authors suggesting that the "Covid kit" (including ivermectin and chloroquine as prevention/treatment) promoted by the government may have contributed to reduced adherence to vaccination (Silva et al. , 2023).
While prior research has not explicitly examined the connection between Covid-19 vaccination intentions and dengue-related misinformation, our findings align with previous authors who suggest that misinformation and conspiracy theories can negatively impact overall vaccination uptake (Allington et al., 2021). The observed lack of association between dengue vaccination intentions and dengue misinformation may be attributed to the small sample size (n = 7) of individuals who did not intend to vaccinate their children against dengue.
Our indings also reveal that right-wing individuals were moderately more inclined to believe in Covid-19 supervirus, dengue GMO, and ivermectin misinformation, being strongly more inclined to believe in both Covid-19 misinformation about vaccine side-effects and ivermectin as prevention/treatment. These indings align with previous national and international research linking right-wing ideology and political conservatism to increased susceptibility to Covid-19 misinformation in Ireland, Mexico, Spain (Roozenbeek et al., 2020), USA (Calvillo et al., 2020), and Brazil (Ramos et al., 2022). In addition, in April 2024 we searched Pubmed, Scopus, Web of Science, and the Virtual Health Library using broad keywords (i.e. , misinformation and dengue) to discuss our indings regarding dengue misinformation and political views. Unfortunately, we were unable to ind papers to discuss our indings, our searches retrieved only between eight and 46 papers in each database. The scarcity of studies in this area highlights a signiicant knowledge gap and underscores the need for further national and international research to investigate potential links between political views and dengue misinformation beliefs.
We also found that individuals who search health information on social media demonstrated a slightly increased likelihood of endorsing Covid-19 misinformation but not dengue misinformation. This inding aligns with a systematic review indicating that reliance on social media is associated with greater susceptibility to health misinformation compared to individuals who trust healthcare professionals or scientists (Nan et al., 2022). However, as only one study within this review originated from Brazil (Carey et al., 2020), further Brazilian studies are warranted to investigate the predictive role of social media use in the belief in health-related misinformation.
Our analysis of control and sociodemographic variables revealed a limited impact on misinformation beliefs. Health professionals exhibited a slight tendency to disbelieve in ivermectin as a Covid-19 prevention or treatment. No significant associations were found between misinformation beliefs and other variables, including profession (i.e., healthcare professional vs. non-healthcare professional), social media use, gender, and information search behavior during the survey. These findings align with previous Brazilian studies documenting off-label treatment recommendations and anti-vaccination stances among healthcare professionals (Hentschke-Lopes et al. , 2022; Silva et al. , 2023; Paumgartten & Oliveira, 2020), as well as by the Brazilian Health Minister during the Covid-19 pandemic period (Martins-Filho & Barberia, 2022).
It is noteworthy that in addition to misinformation about dengue vinegar being the second least believed, this misinformation has no signiicant association with any sociodemographic or health-related outcomes. On the other hand, although misinformation about ivermectin for the prevention/treatment of dengue was the least believed, we found associations with sociodemographic and health-related outcomes. This discrepancy may be attributed to the widespread dissemination of ivermectin-related misinformation during the Covid-19 pandemic, which likely primed individuals to accept similar claims in the context of dengue (Hentschke-Lopes et al., 2022; Silva et al., 2023; Paumgartten & Oliveira, 2020). Given the recent emergence of dengue vaccine misinformation (MS, 2024), it is reasonable to infer that when large-scale vaccination begins, there may also be an increase in the dissemination of misinformation challenging the efficacy of dengue vaccines in Brazil. Therefore, proactive measures targeting the public and healthcare professionals are warranted to prevent the proliferation of these harmful narratives and their potential impact on vaccine uptake and public health outcomes.
Lastly, it is essential to interpret our indings within the context of the study's limitations. The sample, primarily composed of middle-aged to older adults from upper-middle and high-income backgrounds with higher education, may not accurately represent the broader Rio de Janeiro population. Furthermore, we had a limited number of healthcare professionals (n = 21) in the sample. Therefore, findings related to differences between healthcare professionals and the general RJ population should be interpreted with caution. To address these limitations, future research should involve larger, more representative samples of the general population and healthcare professionals across diverse socioeconomic and demographic strata within Brazil.
Conclusion
In sum, the current paper is valuable because it has some strengths. The main one is that, as far as we know, this is the irst study investigating possible differences in levels of belief in misinformation about Covid-19 and dengue, as well as associations between sociodemographic, health-related outcomes and beliefs in misinformation regarding dengue. We found preliminary evidence indicating that the RJ population may hold stronger beliefs in Covid-19 misinformation compared to dengue misinformation, with right-wing individuals exhibiting heightened susceptibility to both. These results hint at a potential consolidation of certain misinformation as factual knowledge, possibly influenced by the pervasive misinformation landscape during the pandemic. Alternatively, the sustained prevalence of Covid-19 misinformation compared to other health issues may contribute to this disparity. Further studies should address these hypotheses.
Additionally, our indings indicate a positive correlation between the number of Covid-19 vaccine doses received and lower susceptibility to any presented misinformation. Conversely, higher levels of misinformation belief were associated with decreased intention to receive both Covid-19 and dengue vaccines, as well as reduced intent to vaccinate children against Covid-19, but not for dengue. Individuals who searched for health information on social media were slightly more inclined to believe in all Covid-19 misinformation, but not in any of the dengue misinformation. Although healthcare professionals demonstrated slightly lower belief in ivermectin as a Covid-19 treatment, trust in vaccines, information from healthcare professionals, and mainstream media emerged as key factors influencing both belief and disbelief in misinformation related to both Covid-19 and dengue.
Given the observed disparities in misinformation beliefs between dengue and Covid-19, and the pivotal role of trust in healthcare professionals and information sources, further research is imperative to elucidate the impact of misinformation disseminated by both health authorities and professionals on public perceptions and behaviors related to Covid-19 and arboviruses. A deeper understanding of the mechanisms through which misinformation influences health-related beliefs and behaviors is crucial. Moreover, developing effective strategies to counter misinformation propagated by these trusted sources, as well as addressing the underlying denialism that may fuel its spread, represents a critical public health challenge.
