Research ArticleSOCIAL SCIENCES

The effects of corrective information about disease epidemics and outbreaks: Evidence from Zika and yellow fever in Brazil

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Science Advances  29 Jan 2020:
Vol. 6, no. 5, eaaw7449
DOI: 10.1126/sciadv.aaw7449
  • Fig. 1 Zika disease beliefs and conspiracy theory endorsement (representative survey).

    Means and 95% confidence intervals from the Brazil wave of the 2016 and 2017 AmericasBarometer survey (n = 1532; 5 April to 11 May 2017). “T” and “F” indicate true and false, respectively, for the outcome measures.

  • Table 1 Correlates of Zika beliefs and misperceptions (survey data).

    *P < 0.05, **P < 0.01, ***P < 0.005 (two-sided); OLS models estimated using survey weights. Data from the Brazil wave of the 2016 and 2017 AmericasBarometer survey (n = 1532; 5 April to 11 May 2017). Outcome variables are measures of factual belief about Zika and a composite measure indicating greater misperceptions about Zika, respectively (see the Supplementary Materials for wording). Respondents ages 16 to 30 are the reference category for age, and the north is the excluded category for region.

    Spreads via mosquitoSpreads via sexSpread via casual contactMisperception beliefs
    (mean)
    Years of schooling0.01−0.05***−0.05***−0.08***
    (0.01)(0.01)(0.01)(0.01)
    Moderate income−0.04−0.22*−0.15−0.05
    (quartile 2)(0.05)(0.10)(0.08)(0.07)
    Medium income−0.01−0.17−0.17−0.16*
    (quartile 3)(0.06)(0.13)(0.09)(0.08)
    High income0.01−0.25*−0.14−0.14
    (quartile 4)(0.06)(0.11)(0.08)(0.08)
    Male0.060.000.02−0.13*
    (0.04)(0.08)(0.06)(0.05)
    Age 31–450.08−0.07−0.060.03
    (0.04)(0.08)(0.06)(0.06)
    Age 46–600.00−0.16−0.08−0.09
    (0.06)(0.11)(0.07)(0.08)
    Age 61 or older−0.050.070.24*0.05
    (0.08)(0.14)(0.11)(0.09)
    Urban0.06−0.08−0.20***−0.05
    (0.07)(0.09)(0.07)(0.07)
    Northeast region0.030.070.18***0.14
    (0.08)(0.11)(0.06)(0.08)
    Center-west region−0.050.140.160.05
    (0.09)(0.13)(0.10)(0.10)
    Southeast region0.020.26*0.20***0.15
    (0.06)(0.10)(0.06)(0.08)
    South region−0.01−0.080.110.03
    (0.08)(0.13)(0.07)(0.09)
    Constant3.53***2.75***2.07***3.31***
    (0.10)(0.18)(0.11)(0.12)
    R20.010.050.070.14
    n1402133113911284
  • Table 2 Correction effects on targeted Zika misperceptions.

    *P < 0.05, **P < 0.01, ***P < 0.005 (two-sided); OLS models with robust standard errors. Respondents are separate samples from Survey Sampling International’s online panel in Brazil. For each outcome measure, higher values indicate greater belief in the claim or claims in question [measured on a Likert scale ranging from “not at all accurate” (1) to “very accurate” (4); see the Supplementary Materials for wording]. All outcome measures are false.

    Misperception beliefs
    (mean)
    GMO mosquitoes caused
    outbreak
    Larvicides responsible for
    microcephaly
    Vaccines responsible for
    microcephaly
    A. 2017 Zika experiment
    Myths correction−0.00−0.080.020.07
    (0.04)(0.06)(0.05)(0.05)
    Constant1.69***1.92***1.63***1.53***
    (0.03)(0.04)(0.04)(0.04)
    n1249126012541255
    B. 2018 Zika experiment
    Myths correction−0.06−0.19***0.010.01
    (0.05)(0.06)(0.06)(0.06)
    Constant (placebo)1.68***1.89***1.62***1.55***
    (0.03)(0.05)(0.04)(0.04)
    n1049105910621058
  • Table 3 Correction effects on other Zika beliefs.

    *P < 0.05, **P < 0.01, ***P < 0.005 (two-sided); OLS models with robust standard errors. Respondents are members of Survey Sampling International’s online panel in Brazil. For each outcome measure, higher values indicate greater belief in the claim or claims in question [measured on a Likert scale ranging from “not at all accurate” (1) to “very accurate” (4); see the Supplementary Materials for wording]. “T” and “F” indicate true and false, respectively, for the outcome measures.

    (A) 2017 Zika experiment
    Causes neurological
    problems (T)
    Spreads
    via
    mosquito
    bite (T)
    Spreads via sexual
    contact (T)
    Spread via casual contact (F)
    Myths correction−0.22***−0.09***−0.03−0.10***
    (0.06)(0.03)(0.07)(0.03)
    Constant (placebo)3.01***3.85***1.98***1.25***
    (0.04)(0.02)(0.05)(0.03)
    n1259126112601261
    (B) 2018 Zika experiment
    Causes
    neurological
    problems (T)
    Spreads
    via
    mosquito
    bite (T)
    Spreads
    via sexual
    contact (T)
    Spread via
    casual
    contact (F)
    Weak
    immune more
    vulnerable (F)
    Transmit
    Zika in
    utero (T)
    Zika increases
    microcephaly (T)
    Get Zika
    from
    donated
    blood (T)
    Microcephaly
    causes
    paralysis (F)
    Myths
    correction
    −0.20***−0.13***−0.04−0.04−0.04−0.15*−0.19***−0.12−0.10
    (0.06)(0.04)(0.07)(0.04)(0.07)(0.06)(0.04)(0.07)(0.06)
    Constant
    (placebo)
    3.00***3.83***1.86***1.26***2.71***3.37***3.69***2.54***2.82***
    (0.04)(0.02)(0.05)(0.03)(0.05)(0.04)(0.03)(0.05)(0.04)
    n105910611053106110571056105610591062
  • Table 4 2018 yellow fever experiment results.

    *P < 0.05, **P < .01, ***P < .005 (two-sided); OLS models with robust standard errors. Respondents are members of Survey Sampling International’s online panel in Brazil. For each outcome measure, higher values indicate greater belief in the claim or claims in question [measured on a Likert scale ranging from “not at all accurate” (1) to “very accurate” (4); see the Supplementary Materials for wording]. “Misperception belief” is a composite measure calculated as the mean of the three items listed. All misperception measures are false. “T” and “F” indicate true and false, respectively, for the other outcome measures.

    (A) Correction effects on targeted yellow fever misperceptions
    Misperception beliefs
    (mean)
    Yellow fever vaccine
    ineffective
    Life-threatening
    side effects
    Propolis protects from yellow fever
    Myths correction−0.20***−0.03−0.20***−0.38***
    (0.04)(0.06)(0.06)(0.06)
    Constant (placebo)1.98***1.82***2.00***2.13***
    (0.03)(0.04)(0.04)(0.04)
    n1063107210721075
    (B) Correction effects on other yellow fever beliefs
    Spreads
    via
    mosquito
    bite (T)
    No
    effective
    vaccine (F)
    Same
    mosquito as
    Zika (T)
    Symptoms
    include
    fever,
    vomiting (T)
    Disease
    can be
    fatal (T)
    Government
    recommends
    vaccine (T)
    Yellow fever
    in cities (T)
    Vaccine
    causes
    immune
    damage (F)
    Hoax by
    drug
    companies (F)
    Myths
    correction
    0.040.010.36***0.02−0.07*0.110.03−0.14*0.03
    (0.04)(0.05)(0.06)(0.04)(0.04)(0.06)(0.04)(0.06)(0.05)
    Constant
    (placebo)
    3.77***1.55***3.10***3.68***3.82***3.09***3.51***2.01***1.45***
    (0.03)(0.03)(0.05)(0.02)(0.02)(0.04)(0.03)(0.04)(0.03)
    n106810771070107510731073107310741068

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/5/eaaw7449/DC1

    Survey instruments

    Additional results

    Fig. S1. Beliefs about Zika (experimental data).

    Table S1. Study summaries.

    Table S2. Sample statistics.

    Table S3. Treatment effects on Zika beliefs (experimental data).

    Table S4. Treatment effects on Zika attitudes and behavioral intentions.

    Table S5. Correction effects in 2017 Zika experiment (ordered probit).

    Table S6. Treatment effects on Zika beliefs and attitudes (conspiracy predispositions).

    Table S7. Treatment effects on Zika beliefs and attitudes (confidence in government).

    Table S8. Treatment effects on Zika beliefs and attitudes (confidence in Ministry of Health).

    Table S9. Treatment effects on Zika beliefs and attitudes (confidence in medicine).

    Table S10. Treatment effects on Zika beliefs and attitudes (confidence in scientists).

    Table S11. Correction effects on other Zika beliefs in 2017 Zika experiment.

    Table S12. Correction effects on Zika beliefs and attitudes after delay.

    Table S13. Treatment effects on Zika attitudes and behavioral intentions.

    Table S14. Correction effects in 2018 Zika experiment (ordered probit).

    Table S15. Treatment effects on Zika beliefs and attitudes (conspiracy predispositions).

    Table S16. Treatment effects on Zika beliefs and attitudes (confidence in government).

    Table S17. Treatment effects on Zika beliefs and attitudes (confidence in Ministry of Health).

    Table S18. Treatment effects on Zika beliefs and attitudes (confidence in medicine).

    Table S19. Treatment effects on Zika beliefs and attitudes (confidence in scientists).

    Table S20. Correction effects on other Zika beliefs in 2018 Zika experiment.

    Table S21. Treatment effect on perceived ability to discern truth about health/science.

    Table S22. Treatment effects on yellow fever attitudes and behavioral intentions.

    Table S23. Correction effects in 2018 yellow fever experiment (ordered probit).

    Table S24. Treatment effects on yellow fever beliefs and attitudes (conspiracy predispositions).

    Table S25. Treatment effects on yellow fever beliefs and attitudes (confidence in government).

    Table S26. Treatment effects on yellow fever beliefs and attitudes (confidence in Ministry of Health).

    Table S27. Treatment effects on yellow fever beliefs and attitudes (confidence in medicine).

    Table S28. Treatment effects on yellow fever beliefs and attitudes (confidence in scientists).

    Table S29. Treatment effect on perceived ability to discern truth about health/science.

    Table S30. Correction effects on other Zika beliefs by pre-experiment response time.

    Table S31. Correction effects on other Zika beliefs by experimental response time.

    References (4143)

  • Supplementary Materials

    This PDF file includes:

    • Survey instruments
    • Additional results
    • Fig. S1. Beliefs about Zika (experimental data).
    • Table S1. Study summaries.
    • Table S2. Sample statistics.
    • Table S3. Treatment effects on Zika beliefs (experimental data).
    • Table S4. Treatment effects on Zika attitudes and behavioral intentions.
    • Table S5. Correction effects in 2017 Zika experiment (ordered probit).
    • Table S6. Treatment effects on Zika beliefs and attitudes (conspiracy predispositions).
    • Table S7. Treatment effects on Zika beliefs and attitudes (confidence in government).
    • Table S8. Treatment effects on Zika beliefs and attitudes (confidence in Ministry of Health).
    • Table S9. Treatment effects on Zika beliefs and attitudes (confidence in medicine).
    • Table S10. Treatment effects on Zika beliefs and attitudes (confidence in scientists).
    • Table S11. Correction effects on other Zika beliefs in 2017 Zika experiment.
    • Table S12. Correction effects on Zika beliefs and attitudes after delay.
    • Table S13. Treatment effects on Zika attitudes and behavioral intentions.
    • Table S14. Correction effects in 2018 Zika experiment (ordered probit).
    • Table S15. Treatment effects on Zika beliefs and attitudes (conspiracy predispositions).
    • Table S16. Treatment effects on Zika beliefs and attitudes (confidence in government).
    • Table S17. Treatment effects on Zika beliefs and attitudes (confidence in Ministry of Health).
    • Table S18. Treatment effects on Zika beliefs and attitudes (confidence in medicine).
    • Table S19. Treatment effects on Zika beliefs and attitudes (confidence in scientists).
    • Table S20. Correction effects on other Zika beliefs in 2018 Zika experiment.
    • Table S21. Treatment effect on perceived ability to discern truth about health/science.
    • Table S22. Treatment effects on yellow fever attitudes and behavioral intentions.
    • Table S23. Correction effects in 2018 yellow fever experiment (ordered probit).
    • Table S24. Treatment effects on yellow fever beliefs and attitudes (conspiracy predispositions).
    • Table S25. Treatment effects on yellow fever beliefs and attitudes (confidence in government).
    • Table S26. Treatment effects on yellow fever beliefs and attitudes (confidence in Ministry of Health).
    • Table S27. Treatment effects on yellow fever beliefs and attitudes (confidence in medicine).
    • Table S28. Treatment effects on yellow fever beliefs and attitudes (confidence in scientists).
    • Table S29. Treatment effect on perceived ability to discern truth about health/science.
    • Table S30. Correction effects on other Zika beliefs by pre-experiment response time.
    • Table S31. Correction effects on other Zika beliefs by experimental response time.
    • References (4143)

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