Measles Makes a Comeback in Brazil: A Case Study in the Fragility of Public Health
By [Staff Writer]
São Paulo – In a concerning development for public health officials, the state of São Paulo has confirmed 23 cases of measles in 2026 alone, a sharp increase from the mere two cases recorded throughout the entirety of 2025. The majority of these new infections, 20 in total, are concentrated within the capital city of São Paulo, with additional cases reported in the neighboring municipalities of São Bernardo do Campo and Guarulhos. This localized outbreak has prompted health authorities to issue an urgent recommendation for measles vaccination for all individuals between the ages of six months and 59 years in the affected areas, regardless of their prior vaccination history. Though the absolute numbers remain small when compared to the major outbreaks that have historically swept through the country, public health experts view this resurgence as a critical warning sign about the state of collective immunity.
The current situation in São Paulo is not a sudden anomaly but rather the culmination of a steady decline in vaccination coverage that has been building for over a decade. This erosion of immunity long predates the Covid-19 pandemic, with a particularly sharp deterioration noted after 2015. Data from the VacinaBR yearbook, a collaborative project involving the Instituto Questão de Ciência and the Brazilian Society of Pediatrics, illustrates a troubling trend across the entire childhood immunization schedule. While coverage rates showed signs of recovery in 2022 and improved significantly in 2023, no single vaccine in the national schedule managed to reach its target coverage in every Brazilian state during that period. The story of measles is particularly illustrative: the World Health Organization (WHO) estimates that coverage for the first dose of the measles-containing vaccine in Brazil plummeted from a robust 97% in 2014 to a precarious 73% in 2021, before recovering to 90% in 2023 and 96% in 2024, only to fall again to 90% in 2025.
The “why” behind these fluctuation numbers is complex and rooted in a well-known phenomenon often referred to as the “paradox of success.” A measles coverage rate of around 95% is generally considered the threshold necessary to maintain herd immunity and prevent sustained transmission. As diseases like measles, polio, and meningitis become rare due to successful vaccination campaigns, they fade from public consciousness. For a generation that has never witnessed the devastating effects of these illnesses, the diseases become abstract threats, while the vaccine itself remains tangible, often associated with a momentary injection and the possibility of side effects. This dynamic erodes the perceived need for vaccination, transforming it from a communal act of protection into an individual decision that requires an active element of trust.
This trust was severely tested and fractured during the Covid-19 pandemic. Vaccination ceased to be a purely public-health measure and became deeply intertwined with contentious debates over government authority, individual freedom, and scientific credibility. In Brazil, this was acutely visible during the presidency of Jair Bolsonaro, who frequently advocated for personal “freedom,” opposed mandatory vaccination, and promoted alternative, scientifically unproven approaches to managing the health crisis. This political influence had a measurable effect. Research published in the journal Frontiers in Political Science found a strong association between an individual’s political preferences and their knowledge and beliefs about Covid-19, with supporters of the then-president being significantly more likely to accept misinformation and conspiracy theories, a trend that directly translated into lower vaccination uptake in municipalities with high levels of support for him.
The pandemic effectively politicized vaccination in a way not seen before, creating a landscape where scientific evidence became secondary to political allegiance. This new dynamic extended beyond the immediate crisis, with a study of over one million tweets revealing the creation of deeply entrenched, polarized pro- and anti-vaccine communities online. Anti-vaccine actors successfully framed their arguments around populist, anti-science, and anti-establishment narratives, sowing seeds of doubt that continue to influence attitudes today. However, experts caution against viewing this as a simple binary of an “anti-vaccine” public versus a “pro-science” establishment. A national survey from June 2026 reported by Rádio Senado found that while 72.1% of respondents kept their vaccinations up to date, 9.9% were entirely unvaccinated, and another 9.2% had stopped getting vaccinated during the pandemic. The survey also highlighted a generational divide, with only about 62% of younger adults aged 16 to 34 reporting they were up to date on their shots, suggesting a lasting impact on the youngest cohorts.
Ultimately, the return of measles in São Paulo should be viewed less as proof that the Brazilian public has become broadly anti-vaccine, and more as a stark warning about the fragility of trust and the consequences of political interference in public health. The infrastructure to combat this resurgence exists, as Brazil still possesses one of the world’s largest and most successful public immunization programs, and recent data suggests a slow recovery is underway. The challenge is no longer just about supply or access, but about rebuilding confidence in a system that has been deliberately undermined. The path forward requires a concerted effort to depoliticize vaccines and reframe them as a fundamental common good, restoring the credibility of public health institutions in the eyes of a skeptical population. As this outbreak demonstrates, a few missing percentage points of coverage on a national spreadsheet can quickly translate into a tangible public health crisis in a densely populated city, proving that in the fight against infectious disease, complacency is perhaps the most dangerous adversary of all.
