[8] Quarantine has been used since ancient times as a method of limiting the spread of infectious disease.
[citation needed] These antibodies can either be produced naturally by recovering from the disease, or triggered through vaccination or another medical procedure.
[citation needed] Reliable immunity certificates can be used to exempt holders from quarantine and social distancing restrictions, permitting them to travel and work in most areas, including high-risk occupations such as medical care.
[17] In 2021, as COVID-19 vaccines became more publicly accessible, some governments began to authorize health credentials either as a document or in a digital form.
These "vaccine passports" are used to control public access to indoor venues (like bars, restaurants, spas, and casinos) and very large gatherings (like concerts, festivals, and sporting events) and not just to facilitate travel.