Vaccine-related attributes and political characteristics are influential factors in the self-reported likelihood of selecting and receiving a hypothetical COVID-19 vaccine in adult patients in the US, according to a JAMA Network Open article. 803512617

The authors undertook a choice-based conjoint analysis via an online survey conducted on 9 July 2020 to assess participant's self-reported likelihood of selecting and receiving a hypothetical vaccine based on seven attributes: efficacy; duration of protection; major adverse events; minor adverse events; US FDA approval process; country of origin; and political endorsement. Respondents had five choice tasks which each involved evaluating two hypothetical COVID-19 vaccines and selecting one, or neither, with levels of vaccine attributes randomly assigned, and attribute order randomised across participants. If a discrete choice was made between the two vaccine options, a 7-point Likert scale was used to ask how likely the participant was to receive that hypothetical vaccine.

Across all choice sets in the 1971 individuals who completed the full questionnaire, 79% of the 9855 cases resulted in selection of one of the two hypothetical vaccines presented, with neither vaccine selected in 21% of cases. The most important vaccine attribute for selection was increased efficacy, followed by a longer duration of protection and a significantly lower incidence of major adverse events. Participants were less likely to select a vaccine developed outside of the US, particularly from China, or a vaccine approved via FDA emergency use authorisation (EUA) rather than full FDA approval. Endorsement from the Centers for Disease Control and Prevention (CDC) and WHO were associated with higher probabilities of vaccine selection compared with an endorsement by President Trump. Similar results were observed for individual's willingness to receive a hypothetical vaccine, which increased with better vaccine efficacy, reduction in major adverse events, US versus China origin, and endorsement by CDC/WHO versus President Trump. The authors concluded that "[t]hese results may help inform public health campaigns to address vaccine hesitancy when a COVID-19 vaccine becomes available".

In an invited commentary, Dr Douglas Opel et al noted that the study "lands at a critical moment for US public health" as vaccine delivery seems imminent though the US government's Operation Warp Speed initiative to produce and deliver a COVID-19 vaccine by January 2021.803512618

Findings on the influence of vaccine efficacy and safety on public acceptability were not unexpected, with the effect on self-reported uptake of the authorisation process and endorsements in line with previous studies of vaccine uptake during the 2009 H1N1A influenza pandemic. However, the commentary noted that the reduced probability of acceptance for a vaccine made available under the FDA EUA versus full FDA approval process was of particular interest, commenting that this "is extremely pertinent given the stated willingness of the FDA Commissioner to use an EUA for a COVID-19 vaccine". Additionally, this finding aligns with previous knowledge about the association of an EUA with vaccine acceptability, and Opel et al believe the study "likely underestimates the true negative association of an EUA with the probability of COVID-19 vaccine acceptance". Approval of a vaccine via use of an EUA is "nearly unprecedented" and if used, strategies will be required to counter potential negative associations with vaccine acceptance, such as sharing and transparency of data, and increased informed consent considerations.

Another key finding that vaccine acceptability rates are higher when endorsed by public health agencies rather than politicians highlights the need to build trust among the public, which requires "a unified, proactive, highly visible communication structure within federal public health agencies to inform the public on a regular basis about these processes". Opel et al urge caution against interpreting the results as further evidence of vaccine hesitancy spreading, although they note that "vaccine hesitancy and a reluctance to accept a COVID-19 vaccine are not completely distinct" as there is an overlap between them in terms of trust in the systems, processes and people involved in the development, approval, monitoring and endorsement of a vaccine. They encourage public health agencies to "prioritize facilitating a broad understanding among the public of these processes through frequent, consistent, and visible communication", as well as engagement with those groups most affected by the pandemic.