Behavioural evidence on COVID-19 vaccine uptake.

OBJECTIVES: The World Health Organization has declared that COVID-19 is no longer a public health emergency of international concern. Nevertheless, it remains a public health issue, and seasonal vaccinations, at the same time of year as influenza vaccinations, will be necessary. When the first vaccines were administered in 2020, decision-makers had to make assumptions about the best methods to communicate and administer vaccines to increase uptake. Now, a body of evidence can inform these decisions. STUDY DESIGN: A narrative review written by three behavioural scientists who design research for policy. METHODS: We searched the PubMed database for: (i) reviews of interventions to increase uptake of COVID-19 or influenza vaccines and (ii) empirical studies on uptake of COVID-19 and influenza vaccines. In addition, registered trials gathered by a Cochrane scoping review of interventions to increase uptake of COVID-19 vaccines were searched for updated results. RESULTS: Results centre around two aspects of a vaccination campaign of interest to policymakers: communication and administration. Results suggest that communications highlighting the personal benefits of vaccination are likely to be more effective than those highlighting collective benefits. The efficacy of vaccination may be underestimated and stressing efficacy as a strong personal benefit may increase uptake. Keeping vaccines free, sending personalised messages, reminders and prebooked appointment times may also increase uptake. CONCLUSIONS: There is now a body of evidence from behavioural science that suggests how vaccination campaigns for COVID-19 can be structured to increase uptake. These recommendations may be useful to policymakers considering seasonal vaccination campaigns and to researchers generating hypotheses for country-specific trials.

Public misperceptions of COVID-19 vaccine effectiveness and waning: experimental evidence from Ireland.

OBJECTIVES: The study set out to measure public understanding of COVID-19 vaccine effectiveness (VE) and how effectiveness wanes with time since vaccination. Because perceived VE is a strong predictor of vaccine uptake, measuring perceptions can inform public health policy and communications. STUDY DESIGN: Online randomised experiment. METHODS: The study was undertaken in Ireland, which has high vaccination rates. A nationally representative sample (n = 2000) responded to a scenario designed to measure perceptions of COVID-19 VE against mortality. The length of time since vaccination in the scenario was randomly varied across four treatment arms (2 weeks, 3 months, 6 months, and 9 months). RESULTS: The public underestimates VE, with substantial variation in perceptions. A majority (57%) gave responses implying perceived VE against mortality of 0-85%, i.e., below scientific estimates. Among this group, mean perceived VE was just 49%. Over a quarter (26%) gave responses implying perceived VE greater than 95%, i.e., above scientific estimates. Comparing the four treatment groups, responses took no account of vaccine waning. Perceived VE was actually higher 9 months after vaccination than 2 weeks after vaccination. CONCLUSION: Despite high vaccination rates, most of the public in Ireland underestimates VE. Furthermore, the general public has not absorbed the concept of vaccine waning in the months following vaccination. Both misperceptions may reduce vaccine uptake, unless public health authorities act to correct them through improved communication.

Discrimination of the spatial derivatives of horizontal binocular disparity.

Observers discriminated the relative disparity, disparity gradient, and disparity curvature of surfaces defined by horizontal binocular disparity in random-dot stereograms. In experiment 1, thresholds for discriminating the depth of sinusoidal corrugations were very similar for different corrugation frequencies, despite large differences in disparity gradient and disparity curvature. Thus observers used a relative disparity cue in preference to a slant or curvature cue. Experiment 2 isolated the spatial derivatives of disparity by jittering the other available cues, using surfaces with square-wave, triangle-wave, and parabolic-wave profiles. Weber fractions were 4%-10% for relative disparity, 6%-12% for disparity gradient, and 15%-30% for disparity curvature. Experiment 3 confirmed this result for larger surfaces. The study supports the view that human stereoscopic vision aims to represent the local scene relative to the observer, at the expense of computing intrinsic properties of objects, such as curvature.

"The analogy between stereo depth and brightness": a reexamination.

A forced-choice experiment is reported, the results of which demonstrate that the cyclopean analogues of the Hermann grid, the embedded squares, and Mach bands can be readily observed. It is concluded that the earlier failure by Brookes and Stevens to observe these cyclopean analogues does not prove that spatial filtering of horizontal disparity is fundamentally different from the spatial filtering of the luminance image.