Reinfection with COVID-19 can occur as soon as several weeks after a previous infection, although this is rare. The immune response from an initial infection typically offers protection for several months, but this protection wanes over time, and new variants can increase reinfection risk. Recent guidelines in some places, like New South Wales, Australia, have reduced the recognized reinfection period from 12 weeks to 4 weeks after the initial infection. Reinfections tend to be milder but can still transmit the virus to others. Vaccination and booster shots help reduce the risk and severity of reinfections.