It is time to get serious about vaccine confidence
Authors: Daniel A Salmon, Matthew Z Dudley
Journal: The Lancet (2020)

Vaccination has had a tremendous impact on the health of the global population.1Ten great public health achievements—United States, 2001–2010.MMWR Morb Mortal Wkly Rep. 2011; 6061923Google Scholar However, history is filled with examples where concerns about the safety and necessity of vaccination led to drops in immunisation coverage and resurgence of disease.2Gangarosa EJ Galazka AM Wolfe CR et al.Impact of anti-vaccine movements on pertussis control: the untold story.Lancet. 1998; 35135661Summary Full Text Full Text PDF Scopus (514) Google Scholar, 3Ghinai I Willot C Dadari I Larson HJ Listening to the rumours: what the northern Nigeria polio vaccine boycott can tell us ten year on.Glob Public Health. 2013; 8113850Crossref Scopus (98) Google Scholar, 4Phadke VK Bednarczyk RA Salmon DA Omer SB Association between vaccine refusal and vaccine-preventable diseases in the United States: a review of measles and pertussis.JAMA. 2016; 315114958Crossref Scopus (422) Google Scholar In 2019, WHO declared vaccine hesitancy as one of the top ten global health threats.5WHOTen threats to global health in.https://www.who.int/emergencies/ten-threats-to-global-health-in-2019Date: 2019Date accessed: July 10, 2020Google Scholar In The Lancet, Alexandre de Figueiredo and colleagues6de Figueiredo A Simas C Karafillakis E Paterson P Larson HJ Mapping global trends in vaccine confidence and investigating barriers to vaccine uptake: a large-scale retrospective temporal modelling study.Lancet. 2020; (published online Sept 10.)https://doi.org/10.1016/S0140-6736(20)31558-0Summary Full Text Full Text PDF PubMed Scopus (400) Google Scholar map global trends in vaccine confidence between 2015 and 2020 using data from 290 surveys, in 149 countries, and among 284 381 individuals aged 18 years or older. They report that confidence in the importance, safety, and effectiveness of vaccines has fallen in many countries.6de Figueiredo A Simas C Karafillakis E Paterson P Larson HJ Mapping global trends in vaccine confidence and investigating barriers to vaccine uptake: a large-scale retrospective temporal modelling study.Lancet. 2020; (published online Sept 10.)https://doi.org/10.1016/S0140-6736(20)31558-0Summary Full Text Full Text PDF PubMed Scopus (400) Google Scholar For example, in 2015 the Philippines ranked in the top ten countries worldwide in rating vaccines safe, important, and effective. But in 2017, a newly introduced vaccine for dengue (Dengvaxia) was given to nearly 850 000 children before it was recognised that the vaccine posed a risk to previously unexposed people. This caused one of the largest falls in vaccine confidence identified by de Figueiredo and colleagues, and subsequently affected uptake of routine vaccines. Fortunately, confidence in vaccines has since risen in the Philippines, although not back to 2015 levels, particularly in terms of perceptions around vaccine safety and effectiveness.6de Figueiredo A Simas C Karafillakis E Paterson P Larson HJ Mapping global trends in vaccine confidence and investigating barriers to vaccine uptake: a large-scale retrospective temporal modelling study.Lancet. 2020; (published online Sept 10.)https://doi.org/10.1016/S0140-6736(20)31558-0Summary Full Text Full Text PDF PubMed Scopus (400) Google Scholar Unlike this example of Dengvaxia, most vaccine safety scares are not supported by scientific evidence. For example, by 2019, there were 16 methodologically sound, controlled epidemiological studies exploring an association between autism spectrum disorder (ASD) and receipt of the measles, mumps, and rubella vaccine, thimerosal in vaccines, and simultaneous vaccination. These studies were conducted by a broad range of investigators, using a wide variety of methods and among different study populations globally—none of these studies found an association between childhood vaccines and ASD.7Dudley MZ Halsey NA Omer SB et al.The state of vaccine safety science: systematic reviews of the evidence.Lancet Infect Dis. 2020; 20: e80-e89Summary Full Text Full Text PDF PubMed Scopus (49) Google Scholar Nonetheless, a substantial proportion, perhaps up to 30%,8Kennedy A Lavail K Nowak G Basket M Landry S Confidence about vaccines in the United States: understanding parents' perceptions.Health Aff (Millwood). 2011; 30: 1151-1159Crossref PubMed Scopus (248) Google Scholar of the public continue to believe childhood vaccines cause ASD. The persistence of this belief despite overwhelming evidence has led some to conclude the science does not matter in affecting public opinion. However, if we consider when these concerns on vaccine safety were first raised and how long it took for the scientific community to address them, it becomes clear that the science was slow.9Lavail KH Kennedy AM The role of attitudes about vaccine safety, efficacy, and value in explaining parents' reported vaccination behavior.Health Educ Behav. 2013; 4054451Crossref Scopus (37) Google Scholar The development of robust scientific evidence takes time, whereas anecdote, sensationalism, and weak science travel quickly. It is difficult to change someone's mind when they have already reached a conclusion, and researchers and research evidence need to inform views among members of the public as they are being formed. As with the science, communications around the autism controversy were reactive and lacked coordination. Vaccine perceptions and disease outbreaks are often localised issues and as such it is vital to have serial, cross-sectional surveys that can identify issues within communities, countries, and regions. de Figueiredo and colleagues' study6de Figueiredo A Simas C Karafillakis E Paterson P Larson HJ Mapping global trends in vaccine confidence and investigating barriers to vaccine uptake: a large-scale retrospective temporal modelling study.Lancet. 2020; (published online Sept 10.)https://doi.org/10.1016/S0140-6736(20)31558-0Summary Full Text Full Text PDF PubMed Scopus (400) Google Scholar benefits from a very large amount of global data with multiple timepoints to examine changes over time. Limitations include vaccination status based on parental recall that might not allow analyses on a vaccine or child-by-child basis. Linkages between measures of vaccine confidence and vaccine uptake are important for understanding the impact of perceptions in the context of other cultural and health system factors. As de Figueiredo and colleagues point out, "Having a common metric of confidence and a baseline for comparison is crucial to understanding these changing trends over time, which can serve as an early warning system to prompt needed intervention to avert drops in vaccine confidence and acceptance."6de Figueiredo A Simas C Karafillakis E Paterson P Larson HJ Mapping global trends in vaccine confidence and investigating barriers to vaccine uptake: a large-scale retrospective temporal modelling study.Lancet. 2020; (published online Sept 10.)https://doi.org/10.1016/S0140-6736(20)31558-0Summary Full Text Full Text PDF PubMed Scopus (400) Google Scholar In the context of an infectious disease pandemic, such an early warning system is needed now more than ever. The perceived safety of vaccination is fundamentally linked to vaccine confidence.10Offit PA Vaccine misinformation (slide 91). National Vaccine Advisory Committee, Washington, DCJune 4–5, 2019https://www.hhs.gov/sites/default/files/2019-6-4%20NVAC_June2019_Panel3.pdfDate accessed: July 16, 2020Google Scholar Vaccines have a remarkable safety record, based on rigorous processes of phased randomised controlled trials and on licensure requirements, which have ensured that the benefits of vaccination outweigh the risks. Situations such as Dengvaxia are exceedingly rare. Still, adverse reactions that are uncommon, have delayed onset, or occur in subpopulations excluded from or inadequately powered in such studies require post-licensure study. Additionally, adverse events following immunisation are often perceived as being caused by vaccines solely on the basis of the temporal relationship,11Black S Eskola J Siegrist CA et al.Importance of background rates of disease in assessment of vaccine safety during mass immunisation with pandemic H1N1 influenza vaccines.Lancet. 2009; 374211522Summary Full Text Full Text PDF Scopus (202) Google Scholar and rapid and rigorous science is needed to determine if they are causally related to vaccination or simply coincidental. Such research is facilitated by active surveillance and requires adequate resources. There is no shortage of strategic plans to improve vaccine safety and communication infrastructure. The US Department of Health and Human Services in 1999,12National Vaccine Advisory CommitteeNVAC resolution: vaccine safety action plan. Jan 12, 1999. US Department of Health and Human Services, Washington, DC1999Google Scholar its National Vaccine Advisory Committee in 2011,13National Vaccine Advisory CommitteeDraft white paper on the United States vaccine safety system (final).https://www.hsdl.org/?view&did=700500Date: September, 2011Date accessed: July 14, 2020Google Scholar and WHO in 201214WHOGlobal vaccine safety blueprint. World Health Organization, Geneva2012Google Scholar all offered strategic planning with warnings of returning measles outbreaks. Unfortunately, these plans were never fully funded or implemented, so progress towards achieving their recommendations has been slow and incremental. WHO is preparing to launch a Global Vaccine Safety Blueprint 2.0 with strategic areas around governance and systems development, coordination, regulation, surveillance, communications, and fragile states and emergencies.15WHOGlobal vaccine safety blueprint 2.0 (GVSB2.0). Draft 1 for public consultation.https://www.who.int/vaccine_safety/Draft_GVSB2.0_20190929.pdf?ua=1Date: Sept 28, 2019Date accessed: July 14, 2020Google Scholar We must ensure this plan does not meet the same fate. People worldwide now eagerly await a vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to curb the COVID-19 pandemic and allow the return to normal social and economic activities.16Schoch-Spana M Brunson E Long R Ravi S Ruth A Trotochaud M on behalf of the Working Group on Readying Populations for COVID-19 VaccineThe public's role in COVID-19 vaccination: planning recommendations informed by design thinking and the social, behavioral, and communication sciences. Johns Hopkins Center for Health Security, Baltimore, MD2020Google Scholar However, without substantial global investment in active vaccine safety surveillance, continuous monitoring of public perceptions, and development of rapid and flexible communication strategies, there is a risk of SARS-CoV-2 vaccines never reaching their potential due to a continued inability to quickly and effectively respond to public vaccine safety concerns, real or otherwise.17Kochhar S Salmon DA Planning for COVID-19 vaccines safety surveillance.Vaccine. 2020; (published online July 10.)https://doi.org/10.1016/j.vaccine.2020.07.013Crossref Scopus (37) Google Scholar With every crisis comes opportunity; it should not be ignored. Global investment in vaccine safety and communication infrastructure is much needed. DAS reports grants from the National Institutes of Health, WHO, and Walgreens and other support from Merck, outside of the submitted work. MZD reports grants from the National Institutes of Health, the Bill & Melinda Gates Foundation, WHO, and Walgreens and consulting with Brighton Collaboration, outside of the submitted work. Mapping global trends in vaccine confidence and investigating barriers to vaccine uptake: a large-scale retrospective temporal modelling studyTo our knowledge, this is the largest study of global vaccine confidence to date, allowing for cross-country comparisons and changes over time. Our findings highlight the importance of regular monitoring to detect emerging trends to prompt interventions to build and sustain vaccine confidence. Full-Text PDF Open Access