We could not find precise estimates about that. However, based on data from the National Regulatory Agency for Private Health Insurances and Plans (ANS – Agência Nacional de Saúde Suplementar), we estimated that by the end of 2018, around 77% of the population were not covered by private health insurance (National Regulatory Agency for Private Health Insurances and Plans, 2019b).

References:

National Regulatory Agency for Private Health Insurances and Plans, M. (2019b). Caderno de Informação da Saúde Suplementar: Beneficiários, operadoras e planos. Março 2019. https://www.gov.br/ans/pt-br/arquivos/acesso-a-informacao/perfil-do-setor/dados-e-indicadores-do-setor/informacoes-gerais/total-cad-info-jun-2019.pdf