This term refers to someone who has gotten sick and developed an immune defense against the disease-causing pathogen.
Vaccines help a body develop immune defense without the risk of illness.
The term is misused by those opposed to vaccines to suggest that a vaccine is causing someone to become ‘unnaturally’ immune to a disease, suggesting it is undesirable or dangerous. Immunologists suggest journalists use the words ‘infection-acquired’ immunity, rather than ‘natural’ immunity. Some immunologists have started using the word ‘hybrid-immunity’ referring to someone who has had SARS-CoV-2 infection and is vaccinated.