Symptoms of long-term COVID can persist for up to two years after the infection has occurred

Approximately 23% of people infected with SARS-CoV-2 between 2021 and 2023 developed long-term COVID, with more than half of them having symptoms persisting for two years. These are the main findings of a study conducted by ISGlobal in collaboration with the Instituto de Investigaciones Trias y Puyol (IGTP) as part of the European END-VOC project.

According to the results, published in the journal BMC Medicine, the risk of developing long-term COVID depends on several factors.

After overcoming primary SARS-CoV-2 infection, some people develop long-term COVID. It is manifested by symptoms that persist for at least three months, including respiratory, neurological, digestive or general symptoms such as fatigue and exhaustion. Most studies of long-term COVID have been conducted in clinical settings, which does not always fully reflect its impact on the general population.

“The population-based cohort study allowed us to better assess the magnitude of long-term COVID and identify risk and protective factors,” explains Manolis Kogevinas, a researcher at ISGlobal and lead author of the study.

The study involved 2,764 adults from the COVICAT cohort, a population-based study designed to characterize the impact of the pandemic on the health of the Catalan population. Participants completed three questionnaires – in 2020, 2021 and 2023 – and provided blood samples and medical records.

Risk factors and preventive measures

“Being female, having had a severe COVID-19 infection, and having chronic diseases such as asthma are obvious risk factors,” says Marianna Karachaliou, study co-author and ISGlobal researcher. ” “In addition, we noticed that people who were obese and had high levels of IgG antibodies before vaccination were more prone to develop long-term COVID,” she adds. “The latter factor may reflect hyperactivation of the immune system after primary infection, which in some cases may contribute to the persistence of long-term symptoms.’

The analysis also identified protective factors that may reduce the risk of developing the disease. These included vaccination prior to infection and a healthy lifestyle that includes regular physical activity and adequate sleep.

In addition, the risk was lower in people who became infected after the omicron variant became dominant. This may be due to a tendency toward a milder course of infection or a higher overall immunity to COVID-19.

Three subtypes of long-lasting COVID

Based on the symptoms reported by the experimental participants and their medical records, the researchers identified three clinical subtypes of long-term COVID.

These were categorized according to whether symptoms were from the nervous system and musculoskeletal system, the respiratory system, and whether they were severe and involved multiple organs. In addition, the researchers found that 56% of people with long-term COVID still had symptoms after two years.

“Our results show that a significant proportion of the population has long-term COVID, which in some cases affects quality of life,” said Judith Garcia-Aymerich, a researcher at ISGlobal and the study’s most recent author.

“Establishing collaborations with other countries will be key to understanding whether these results can be extrapolated to other populations,” she concludes.

On the fifth anniversary of COVID-19, significant progress has been made in understanding the disease. However, as this study shows, the impact of the pandemic on mental health, work and quality of life remains profound. While this study is a step forward, there is still much work to be done to fully understand this “invisible” disease.

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Published: 15.03.2025

Updated: 14.03.2025

Medical author, Medical editor:

Stepan Yuk

Medical expert:

PhD. Olexandr Voznyak