Long COVID, or Post-Acute Sequelae of COVID-19 (PASC), describes health problems that persist for weeks, months, or even years after the initial infection. These symptoms can be new, a continuation of issues from the acute illness, or can return after a period of feeling recovered. Understanding the factors that elevate a person’s chances of developing this condition is a focus of ongoing research. The development of Long COVID is not random, as certain elements of the initial illness, an individual’s health profile, and their biological makeup influence susceptibility.
Initial Infection Characteristics
The severity of the initial COVID-19 illness is a predictor of developing lasting symptoms. Individuals who require hospitalization or admission to an intensive care unit (ICU) face a greater likelihood of experiencing Long COVID. This connection suggests that a more intense initial assault by the virus on the body can lead to prolonged recovery and persistent health issues.
Beyond overall severity, the variety of symptoms experienced early in the infection also plays a role. Research indicates that individuals who report five or more symptoms during the first week of their illness are more likely to develop Long COVID. A higher viral load during the early stages has also been identified as a factor that can increase this risk.
Pre-existing Medical Conditions
An individual’s health status before contracting COVID-19 is a determinant of their risk for developing long-term symptoms. Several pre-existing, or comorbid, conditions have been linked to a higher probability of Long COVID. These chronic health issues often create a baseline of physiological stress or inflammation in the body, which the viral infection can worsen.
Among the most prominent conditions is Type 2 diabetes, which can impact immune function and circulation. Cardiovascular diseases, including high blood pressure, place a strain on the body that makes it more vulnerable to the lingering effects of the virus. Respiratory conditions like asthma and chronic obstructive pulmonary disease (COPD) also increase the risk.
Obesity is another factor identified in numerous studies. Fat tissue is metabolically active and can promote a state of chronic, low-grade inflammation that may be amplified by the immune response to COVID-19. Autoimmune diseases, such as lupus and rheumatoid arthritis, are also associated with a greater chance of developing the condition.
Demographic and Biological Markers
Certain inherent traits and biological responses are linked to an increased risk of developing Long COVID. Studies have consistently shown that being female is associated with a higher likelihood of experiencing long-term symptoms, and differences in immune responses between sexes are thought to play a part. Older age has also been identified as a risk factor, potentially due to age-related changes in immune function and a reduced capacity for recovery.
Specific biological markers found in some individuals also appear to predispose them to Long COVID. One such factor is the presence of specific autoantibodies, which are immune proteins that mistakenly attack the body’s own tissues. Research suggests the infection could trigger or amplify an autoimmune-like response that contributes to lasting symptoms.
Another biological finding is the reactivation of latent viruses already present in the body. The Epstein-Barr virus (EBV), a common virus that causes mononucleosis, has been a particular focus. The stress of a COVID-19 infection can cause EBV to reactivate, and this is associated with a higher incidence of Long COVID, particularly symptoms like fatigue and cognitive issues.
Role of Vaccination and Reinfection
Events that occur after an initial infection can modify the risk of developing Long COVID. Research shows that individuals who are vaccinated before being infected have a lower risk of developing Long COVID compared to those who are unvaccinated. This suggests the vaccine-primed immune response may be more effective at controlling the virus and reducing the severity of the initial illness.
The effect of reinfection on Long COVID risk is complex. Some studies indicate that the risk of developing Long COVID after a second infection is lower than it was for the first infection. However, the cumulative risk appears to increase with each subsequent infection.
This means that while any single reinfection might carry a lower individual risk, getting COVID-19 multiple times still elevates a person’s overall chance of eventually developing Long COVID. Each new infection presents another opportunity for the condition to develop.