Long-Term Effects of COVID-19

  • 1st Revision: Francesca Fitzgerald
  • 2nd Revision: Noor Al- Tameemi
  • 3rd Revision: Sheza Asim

The majority of individuals who contract COVID-19 recover within a short period of time without any lingering health problems. However, some people experience long-term health complications despite the mild symptoms during the infection1

Research into long-term COVID-19 effects is still in its early stages as we do not yet have a complete understanding of what it is and what it isn’t. Still, there are a few commonly reported symptoms by patients, namely extreme fatigue, shortness of breath and joint pain2.  

What is long-term COVID-19?

Long covid, also known as post-acute COVID-19, is an umbrella term for a collection of lingering health problems that continue or develop after acute COVID-19. Experiencing symptoms 4-12 weeks after contracting coronavirus is termed ongoing symptomatic COVID-19. If the symptoms continue or worsen after 12 weeks of acute COVID-19, it is classified as post-covid syndrome

While a conclusive definition is yet to be agreed upon for long-Covid, there are common symptoms that act as potential markers for post-Covid syndrome. The most frequently reported symptoms of long-term COVID-19 include neurological complications, cardiovascular effects, pulmonary impediments and a change in sense of smell. The symptoms categorized by major organ system includes2:

  • General symptoms: extreme fatigue, insomnia, unordinary mood swings, joint pain;
  • Lungs: shortness of breath, chest pain, prolonged dry cough;
  • Nervous system: memory and concentration difficulties (“brain fog”), headache, change in sense of smell;
  • Cardiovascular: heart palpitations;
  • Gastrointestinal: diarrhea, abdominal pain.

Some individuals predominantly experience respiratory symptoms, namely cough and shortness of breath, and fatigue, while others suffer multi-system effects. These complications affect multiple parts of the body including the brain, gut and cardiovascular system3

What causes long-term COVID-19?

It is still unclear why patients experience long-term symptoms and what predisposes some individuals over others to developing them. The majority of experts argue that these long-term effects are caused by a robust inflammatory response – a response in which the immune system goes haywire – in some individuals. 

This immense inflammation is associated with blood clots in the lungs, heart and brain, which may lead to blood vessel damage and subsequent development of long-term health complications4. In other words, long-term COVID-19 could be classified as a self-destructive, autoimmune disease. 

Although this hypothesis seems promising, there are no conclusive answers. Other studies have indicated that even after  COVID-19, fragments of the virus remain in the bloodstream and continue to disrupt different functions in the body in various ways.

Alternative hypotheses suggest that post-covid syndrome could be attributed to multiple disorders combined into one, meaning that it is unlikely that there is one, simple, universally applicable explanation for the long-term effects.  

Who is at risk?

Surveys have indicated that over 1 one in 10 people who had COVID-19 continue to develop ongoing health complications. While there is increasing clarity on the incidence of long-term covid, we are still in the early stages of categorizing which individuals are at greatest risk, and why it only impacts some people and not others. 

There is conflicting evidence on the relationship between acute infection severity and the incidence of long-term COVID-19 symptoms. Some research has indicated that individuals who experienced long-term effects had a moderate-severe case of COVID-19, while other research showed that they were asymptomatic or had only a mild infection1,5.

Studies have suggested long-term COVID-19 becomes increasingly likely with age. Statistics indicated that 10% of below 50-year-olds suffered from long-term Covid, while the incidence increased to 22% for individuals above 703. Being female, having a high BMI (body mass index) and suffering from a pre-covid respiratory condition were also shown to be potential risk factors for lingering health problems6. Still, many ambiguities remain. 

Can the vaccine help reduce the risk of long-term Covid?

It is commonly known that being fully vaccinated against COVID-19 reduces the risk of developing severe symptoms during acute infection. However, research is shedding light on its additional role in lessening the incidence of long-term Covid. 11% of unvaccinated individuals developed ongoing symptoms, while only 5% of fully vaccinated people experienced long-term Covid effects7

However, the data is highly inconsistent and varies between studies; more research is required to confidently conclude the precise effectiveness of the jab in preventing long-term Covid. What we can be certain about, though, is that Covid vaccines are the most effective known method of reducing viral spread, while also reducing the risk of infection severity. 


  1. Logue, J.K., Franko, N.M., McCulloch, D.J., et al. (2021). “Sequelae in Adults at 6 Months After COVID-19 Infection”. JAMA Netw Open. 4(2). 
  2. Halpin, S., O'Connor, R., and Sivan, M. (2021). “Long COVID and chronic COVID syndromes”. Journal of medical virology. 93(3): pp. 1242–1243.
  3. Sudre, C.H., Murray, B., Varsavsky, T., et al. (2021). “Attributes and predictors of Long-COVID: analysis of COVID cases and their symptoms collected by the Covid Symptoms Study App”. medRxiv.
  4. RCSI. (2021). “Blood clotting may be the root cause of Long COVID syndrome, research shows”. ScienceDaily.
  5. Al-Aly, Z., Xie, Y. and Bowe, B. (2021). “High-dimensional characterization of post-acute sequelae of COVID-19”. Nature. 594: pp. 259–264.
  6. Thompson, E.J. Williams, D.M., Walker, A.J., et al. (2021). “Risk factors for long COVID: analyses of 10 longitudinal studies and electronic health records in the UK”. medRxiv.
  7. Antonelli, M., Penfold, R.S., Merino, J. et al. (2021). “Risk factors and disease profile of post-vaccination SARS-CoV-2 infection in UK users of the COVID symptom study app: a prospective, community-based, nested, case-control study”. The Lancet.
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Vicky Stogiannidou

University of Bath, BSc Biology
Vicky Stogiannidou has graduated from the University of Bath with a BSc Biology where she studied topics related to neuroscience, biochemistry and immunity. Vicky has developed a strong interest in health-related fields, one of these being nutrition. Vicky deeply believes that diet is instrumental for optimal health and is the culprit underlying many chronic diseases today. Beyond the keto diet, she has been researching heavy metals, which are found in many food sources and act as toxic catalysts for numerous diseases.

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