Using the data from the first experiment, Figure 1 shows how vaccine timing affects stated willingness to vaccinate and confidence. Panel A shows the results for the overall sample. Compared to a baseline announcement one week after the election, as well as an approval in December, approval before the election reduced willingness to vaccinate and confidence. An announcement of approval one week prior to the election was estimated to decrease the reported likelihood of receiving a COVD-19 vaccine within the first three months of availability by 4.2 points (95% C.I. = -1.6 to -6.8, p < .01), a 14% reduction from reported intentions to vaccinate if announced one week after the election (.042/.298 =.14). Respondents were also less confident that the vaccine would be safe and effective if approved before the election (difference = .049 for scale outcome ranging from 0 to 1, 95% C.I. = -.030 to -.069, p < .001). A vaccine approved in December compared to the week after the election increased willingness to vaccinate by 1.7 points (95% C.I. = -1.5 to 5.0, p= .30) and confidence by .41 units (95% C.I. = .18 to .63, p < .001).
The subsequent panels of Figure 1 show that the effect of the politicized context is based on a strong response among respondents with high general vaccine confidence (Panel B, for high confidence respondents the early announcement reduced uptake intentions by 8.2 points (95% C.I. = -4.0 to -12.4, p < .001) and confidence by .085 units (95% C.I. = -.058 to -.113, p < .001)) and was heavily concentrated among Democrats (Panel C, uptake reduced by 8 points (95% C.I. = -3.9 to -12.1, p < .001) and confidence by -.086 units (95% C.I. = -.058 to -.116, p < .001); Effects for Republicans and Independents smaller and not statistically significant).
For the second experiment, compared to the baseline condition of a positive statement by President Trump, Dr. Fauci’s statements had dramatic effects on public reactions (Figure 2). For vaccine uptake and confidence, respectively, the effects of a positive rather than negative endorsement by Dr. Fauci were very large, approximately 21.6 points (95% C.I. = 17.6 to 25.5, p < .001) and .234 units (95% C.I. = .204 to 264, p < .001). President Trump’s statement in favor rather than opposed was not statistically significant for either outcome. Speaker Pelosi’s co-endorsement with President Trump versus contradicting the President with a negative statement had effects approximately one-third to one half as large as that of Dr. Fauci (vaccine uptake difference = 5.7 points, 95% C.I. = 1.7 to 9.8, p<.001; confidence difference = .067, 95% C.I. = .037 to .098, p < .001).
The effects of Fauci and Pelosi were concentrated among those with a high vaccine confidence (Figure 2), although there was a positive effect from a positive rather than negative statement from Dr. Fauci among both groups. In contrast, the overall null effect of President Trump’s positive rather than negative statement is shown to be a combination of a positive (not significant) increase in confidence among those low in baseline confidence and a negative (significant) effect among those high in confidence.
All groups indicated more willingness to receive a vaccine if Dr. Fauci supported it rather than opposed it, but the effect was 4 times larger for Democrats than Republicans, with the effect for Independents in between. In contrast, President Trump had a polarized effect; his statement in support of versus opposition to vaccine approval raised vaccine confidence among Republicans about as much as Dr. Fauci, but lowered confidence among Democrats and had no effect among independents. Speaker Pelosi’s impact was concentrated among Democratic respondents, with effects near zero for both Republicans and independents.
Given the sensitive nature of pre-election approval, we more closely examine the effect of endorsement by public figures of an approval one week prior to the election (Table S3). Even in the most politicized window for approval, Dr. Fauci’s support increased reported uptake intentions and confidence in safety and efficacy compared to Dr. Fauci opposing a vaccine (vaccine uptake difference = 15.4 points, 95% C.I. = 9.2 to 21.6, p < .001; confidence difference = .201 units, 95% C.I. = .152 to .251, p < .001). Notably, endorsement by political figures does not appear to move vaccine uptake or confidence in safety and efficacy in the pre-election window.