Reinfection with COVID-19 means getting infected, recovering, and then becoming infected again. Immunity from a previous infection is not permanent.
Typical Re-infection Timelines
Immunity acquired from a previous COVID-19 infection tends to decrease over time. While some protection can last for several months, its strength diminishes. Reinfection can occur as early as several weeks after an initial infection, though this is rare.
The Centers for Disease Control and Prevention (CDC) notes that reinfection is possible within 90 days of an initial infection, but most reinfections happen after this period. Some research indicates that the interval between infections can range broadly, with many occurring after about one year.
Factors Influencing Re-infection Risk and Timing
The likelihood and timing of COVID-19 reinfection are influenced by an individual’s immune response. The body produces antibodies to fight the virus. Blood antibodies offer protection against severe disease, while nasal antibodies act as a first line of defense, potentially preventing infection altogether.
These nasal antibodies may decline around nine months after infection, contributing to the risk of repeat infections. The severity of the first illness also plays a role; a mild initial case often leads to a mild reinfection, while a severe initial infection can foreshadow a similarly severe reinfection. A weakened immune system can also increase susceptibility to reinfection.
The Impact of Variants and Vaccination
The evolution of the SARS-CoV-2 virus, particularly new variants, influences reinfection risk. Variants like Omicron and its sub-variants (e.g., BA.4 and BA.5) can evade existing immunity from prior infections.
Vaccination reduces the risk of reinfection and mitigates the severity of subsequent illnesses. Studies show that vaccinated individuals have a lower likelihood of reinfection compared to unvaccinated individuals. This protective effect helps reduce the chances of severe symptoms, hospitalization, or death, even if reinfection occurs. The combination of vaccination and prior infection, known as “hybrid immunity,” provides stronger and more durable protection against future infections and severe disease than either alone.
Recognizing and Responding to Re-infection
Symptoms of COVID-19 reinfection can be similar to those of a first infection, including sore throat, runny nose, cough, fever, muscle aches, and fatigue. Some individuals may experience different symptoms. Reinfections are often mild, but severe illness can still occur.
If reinfection is suspected, testing confirms the virus. Rapid antigen tests or PCR tests can be used. If symptoms reappear, individuals should consider testing and follow recommendations for isolation to prevent further spread. Consulting a healthcare provider is advised if symptoms are severe or concerning.