What Is the Importance of Vaccine Hesitancy in the Drop of Vaccination Coverage in Brazil?

Since the 1990s, the vaccination coverage for children via the Programa Nacional de Imunizações do Brasil (Brazilian National Immunization Program - PNI), which promotes the free vaccination of more than 15 antigens, was above 95%. However, since 2016, such coverage has been declining about 10 to 20 percentage points. Several factors are related to this drop. This article explores the role of anti-vaccine movements, which are growing and being strengthened by the increase in incorrect health information shared especially on the internet. The objective of the article is to present the definition of and factors related to vaccine hesitancy, as well as to discuss its importance in the Brazilian context.

In 2012, the World Health Organization (WHO) formed the Strategic Advisory Group of Experts - Working Group (SAGE-WG) to define vaccine hesitancy, to understand its magnitude and the factors that influence it, and to systematically gather evidence of interventions in public health. The behavioural phenomenon is quite complex compared to its determinants (which involve cultural, social, and economic aspects), and varies over time, over location, and over types of vaccines. This behaviour is influenced by several interrelated factors, such as confidence, complacency, and convenience, known as the "3Cs" model, proposed by WHO in 2011. Despite vaccine hesitancy being a recognised problem, its measurement is still a challenge. Furthermore, systematic reviews have concluded that there is no strong evidence to recommend specific interventions to deal with vaccine hesitancy. In general, most interventions have more than one component, with those directed to the increase in knowledge (communication strategies, media, social mobilisation, information tools for health professionals) standing out.

The article then briefly traces the history of the anti-vaccine movement, which is as old as vaccination itself. In Brazil, the most well-known manifestation was the Revolta da Vacina (Vaccine Revolt) in 1904, with the law of compulsory smallpox vaccination.

Few Brazilian studies have investigated voluntary refusal or delay with regard to vaccines offered through the Brazilian Unified Health System (SUS). The article reviews some of the existing studies, even though they may not refer to the phenomenon as "vaccine hesitancy". Generally, among those who are hesitant, the interpretation of vaccine risk is not based on rational evaluation of the evidence but, rather, on the sense of uncertainties and ambiguities that remain even in the face of empirical evidence. Thus, several studies emphasise the importance of effective communication.

It is noted here that the media has a crucial role to play in people's search for information about vaccines in Brazil. The influence of the media can, ironically, be seen in several examples that had the opposite effect of anti-vaccine messaging. The 2007-2008 yellow fever outbreak was portrayed by the press as an epidemic out of control, with no explanation of the sylvatic form of the disease and emphasis on the vaccine as the only salvation. The result was the indiscriminate pursuit of the population for the vaccine, even by people for whom vaccination was contraindicated. From 2017 to 2018, similar problems were experienced, with an exaggerated demand for the vaccine; however, the introduction of fractional-dose vaccine and dispersal of incorrect news made the queues disappear.

In conclusion, the article stresses that anti-vaccine movements, although ancient, have been gaining strength throughout the world, with a more visible start in high-income countries. However, certainly, the impact of this negative perception regarding vaccines will be more important in low- and middle-income countries (LMICs) as these movements are strengthened. "Therefore, it is imperative that Brazilian public administrators, researchers and the population mobilize themselves to protect our successful immunization program."