Brazil’s Unified Health System (Sistema Único de Saúde - SUS) will be 30 years’ old in 2018. SUS came into being when the 1988 Federal Constitution was enacted, making Brazil the largest country in the world to have a public health system based on the principles of universality, equity and integrality. Despite difficulties it has faced, with every day that has gone by over these three decades SUS has become increasingly indispensable in the lives of Brazilian citizens.

The National Health Survey (2013) shows that the majority of the population (estimated 80%) depends on SUS for healthcare-related actions.^1,2 In the current context, this situation appears unlikely to change in the short term. In view of the current economic crisis, the prevailing unemployment rate (which has remained in excess of 11% of the economically active population) and the recent behaviour of economic growth, private health services are expected to be unaffordable for the majority of people.³ It should be emphasized that SUS is responsible for providing the most vulnerable segments of the population with access to health actions and services, thus working to promote equity.^2,4 SUS also provides services to patients who have health insurance and use private services when they require high complexity care, such as transplants, haemodialysis and high-cost medication.^5,6

Notwithstanding, its universal nature is more evident in its health surveillance actions, which extend to the entire Brazilian population. An example of this is the National Immunization Programme, which offers universal access to all immunobiological products recommended by the World Health Organization. The current national immunization schedule provides for 41 immunobiological products. Immunization actions have resulted in general in the successful control of vaccine-preventable diseases.⁷ Despite the challenges still to be overcome - especially those related to social and regional inequalities -, important progress has been achieved, considering that in the 1980s vaccination coverage for the child immunization schedule was below 50%.⁸

Another example is found in the combination strategies for controlling the HIV epidemic, whereby Brazil is one of the few countries that makes them available for universal access. Thanks to the excellent results achieved through the universal distribution of antiretroviral drugs, Brazil has been indicated as a model for other middle- and low-income countries,⁹ and has even shown better performance than the United States in its response to HIV/AIDS.¹⁰

Moreover, the role of SUS must be highlighted for its health surveillance actions in response to events with the potential to produce Public Health emergencies. The most striking example was the response to the Zika virus emergency in Brazil and to the congenital syndrome epidemic related to Zika infection. Despite the lack of knowledge regarding the aetiology of congenital Zika syndrome at the beginning of the epidemic, SUS coordinated a series of health surveillance, control and care actions which demanded intense political and institutional mobilization and achieved internationally recognized results.¹¹

Owing to its scope, universal nature and results achieved, SUS has drawn the attention of international experts,² who highlight that the combination of restrictive contexts and austerity policies to curb public expenditure, including expenditure on health, may put at risk the progress achieved and the right to health of the majority of the Brazilian population. SUS is a national heritage, a State policy that guarantees the entire population’s access to health actions and services.

By disseminating epidemiological knowledge produced by Brazilian and foreign researchers and health service workers, publishing quality articles offering analyses, evaluations, criticisms and contributions to the enhancement of the services offered by SUS, the Epidemiology and Health Services journal (Epidemiologia e Serviços de Saúde - RESS) takes on an important role in promoting the strengthening of the Brazilian health system. Defending SUS is the duty of all governments, health service managers, civil society organizations, the scientific community and health professionals. Long live SUS!