The impacts on public confidence are likely to be long lasting and experienced globally, says Julie Leask
This week several countries have suspended or delayed the Oxford/AstraZeneca vaccination rollout while investigations consider whether the vaccine is implicated in thromboembolic events. The EMA’s safety committee have just announced the outcome of their investigation, concluding that the Oxford/AstraZeneca covid-19 vaccine is safe and effective, and is not associated with an increased risk of blood clots, although they will continue to monitor this. They also state that there is a possible link to very rare blood clots with low blood platelets.
What began with Norway, Denmark, and Iceland suspending the vaccine on the 11 March 2021, has led to a cascade of countries following suit. It is not completely clear what led regulators to suspend the programmes under limited evidence of harm, but the impacts on public confidence are likely to be long lasting and experienced globally. Once a vaccine is technologically stigmatised, it can often take some time for public confidence to recover.
Vaccine safety is a core component of vaccination programmes. When a vaccine safety signal is detected, countries face a dilemma: suspend the programme now while investigations establish a causal link, or proceed with vaccinating people amidst fears of potential harm. Under conditions of uncertainty, decision makers may prefer to accept harms from omission—not vaccinating, to those from commission—vaccinating. Studies have linked this pattern, known as omission bias, to the sense of responsibility from the commission which intensifies the anticipation of regret.  Countries choosing to suspend may also be affected by their ability to choose other vaccines.
Yet, even if a causal link is found between the Oxford/AstraZeneca covid-19 vaccine and the different thromboembolic events currently being considered, the risk of such outcomes will almost certainly be far outweighed by the risks of covid-19. In the European WHO region alone, currently each week around 20,000 people die from covid-19. For controlling the pandemic globally, the Oxford/AstraZeneca vaccine has some strong attributes: it is easier to store and thus to reach populations in countries without the funding and infrastructure for ultra-cold storage. It is also lower-priced, and real world data from Scotland estimate it has reduced risk of hospitalisation by 94%. 
People’s willingness to have a vaccine will be influenced by its perceived safety. That is why vaccine programme suspensions, even if temporary, have long lasting effects on public confidence.
In 1999, the American Academy of Pediatrics and U.S. Public Health Service US recommended that the hepatitis B birth dose vaccine be suspended due to a theoretical risk of mercury exposure. Reductions in coverage for the birth dose remained persistently lower in the year after the suspension was lifted with an estimated 750,000 fewer newborns being vaccinated. 
Even vaccine suspensions supported by an established causal link can have impacts above and beyond the aversion of harm they seek. In 2010, Australia suspended influenza vaccine for children under 5 years of age after reports of an increase in the rate of febrile convulsions, later established to be linked to a particular brand of vaccine. Despite programme resumption with paediatric vaccines without the increased risk, childhood influenza vaccination rates in Western Australia decreased from 45.5% in 2009 to 7.9% in 2010 and 17.3% in 2011. 
The Oxford/AstraZeneca vaccine suspensions’ impact on confidence is compounded by existing issues with efficacy, supply problems, and pace of rollout. It occurs against a backdrop of relatively high rates of vaccine hesitancy measured in 17 countries by YouGov and Imperial College London including two of the countries that first suspended the vaccine. In Norway, 17% of the population were estimated to be unsure about having a covid-19 vaccine in February, while 11% planned not to. In Denmark these figures were 11% and 7% respectively. Even in countries that have not suspended the vaccine, there will likely be spillover effects on confidence, a particular concern for low income countries where the vaccine’s more feasible storage requirements increase equity of access.
The world cannot afford to have current levels of intended vaccine refusal if it is to gain control over the covid-19 pandemic. The decisions that occur now will be pivotal. Once a causal link and its magnitude is established, governments should carefully weigh their tolerance for risk, make a considered decision in full knowledge of the further impact on public confidence on all covid-19 vaccines, then communicate it clearly and broadly, with transparent and detailed rationales. Vaccine programme decisions should not fall victim to politicisation, which will cause great harm.
Early and frequent updates are of great importance as events unfold. Communicators should not over-reassure with statements that appear to dismiss adverse events concerns, but communicate with empathy. Messages should be clear, cater to different levels of health literacy, and be layered according to information needs. Healthcare worker’s information needs should be prioritised. Misleading information should be rapidly addressed using trusted spokespersons to avoid the development of information voids.  Scientific consensus should be emphasised.  Monitoring community sentiment enables communicators to determine the impact of the issues on different population groups and better respond. Two-way communications that make space to hear questions from audiences ensure that actual, not assumed questions are addressed. 
More broadly, it will not be possible to face the challenges of this global vaccine rollout without an ongoing investment in the social sciences that inform how we monitor and manage vaccine safety issues. It is time for funders to recognise that the research and development of vaccine uptake is as important as the vaccines themselves.
Julie Leask, Professor, University of Sydney School of Nursing and Midwifery, Faculty of Medicine and Health, and Visiting professorial fellow, National Centre for Immunisation Research and Surveillance.
Competing interests: none declared.
- Ritov I, Baron J. Reluctance to vaccinate: omission bias and ambiguity. J Behav Decis Making 1990;3:263-77.
- Vasileiou E, Simpson CR, Robertson C, et al. Effectiveness of first dose of COVID-19 vaccines against hospital admissions in Scotland: national prospective cohort study of 5.4 million people. 2021
- Luman ET, Fiore AE, Strine TW, et al. Impact of thimerosal-related changes in hepatitis B vaccine birth-dose recommendations on childhood vaccination coverage. Jama 2004;291(19):2351-8. doi: 10.1001/jama.291.19.2351 [published Online First: 2004/05/20]
- Mak DB, Carcione D, Joyce S, et al. Paediatric influenza vaccination program suspension: effect on childhood vaccine uptake. Australian and New Zealand Journal of Public Health 2012;36(5):494-95. doi: 10.1111/j.1753-6405.2012.00925.x
- King C, Leask J. The impact of a vaccine scare on parental views, trust and information needs: a qualitative study in Sydney, Australia. BMC Public Health 2017;17(1):106. doi: 10.1186/s12889-017-4032-2 [published Online First: 2017/01/25]
- Lewandowsky S, Cook, J., Schmid, P., Holford, D. L., Finn, A., Leask, J., Thomson, A., Lombardi, D., Al-Rawi, A. K., Amazeen, M. A., Anderson, E. C., Armaos, K. D., Betsch, C., Bruns, H. H. B., Ecker, U. K. H., Gavaruzzi, T., Hahn, U., Herzog, S., Juanchich, M., Kendeou, P., Newman, E. J., Pennycook, G., Rapp, D. N., Sah, S., Sinatra, G. M., Tapper, K., Vraga, E. K. The COVID-19 Vaccine Communication Handbook. A practical guide for improving vaccine communication and fighting misinformation. , 2021.
- World Health Organization. Covid-19 vaccines: safety surveillance manual. Geneva, 2020.