Also spelled vaxident, vaccident or vaxxxident.
Originally referred to an accident happening right after a COVID vaccination, such as a car crash when the driver loses control, goes into cardiac arrest, and/or passes out.
More generally, a vaxxident is an accident or error committed by an individual due to brain fog or neurological damage caused by a COVID vaccination.
vaxxident = vaccination + accident
Colloquially, getting vaccinated by mistake can also be called a vaxident.
Deaths post-vaccination may also be colloquially referred to as vaxxident, such as for example the death of Marvin Hagler.
One of the earliest suspected cases of mass vaxxidents is the Meron incident, during which 50 Israelis died. Israel was one of the first countries to vaccinate most of their citizens.
Prior to the COVID-19 hysteria, a vaccident would have referred to accidentally getting measles.