Competing interests: We have read and understood BMJ policy on declaration of interests and declare the following interests: MCM currently receives research funding from the Leverhulme Trust, Leverhulme Centre for Demographic Science and ERC-2018-ADG-835079 and has received research funding from the ESRC (Economic and Social Research Council)/UKRI (UK Research and Innovation), the NWO (Dutch Research Council), the Social Science and Research Council of Canada, and the European Commission. JS has received research funding from the European Commission (2018, 2020) and the Academy of Finland (2020). He is a member of the Scientific Committee of the annual Vaccine Acceptance Meeting organised by Fondation Merieux. Travel and accommodation expenses related to these meetings have been paid for by Fondation Merieux (2018, 2019). JS is also an unpaid member of the advisory board for Sabin Vaccine Institute’s Vaccine Acceptance Research Network.