A research team led by Professor Yeon Dong-keon from Kyung Hee University (KHU) Medical Center, along with Professor Lee Jin-seok from KHU’s Department of Biomedical Engineering and student research assistant Kim Hyeon-jin, has demonstrated a positive relationship between COVID-19 and allergic diseases. 

The team conducted this research to provide guidance for managing health in the post-COVID-19 era. Their findings were published on April 4, 2024, in the prestigious journal Nature Communications, with an article titled Incident Allergic Diseases in Post-COVID-19 Condition: Multinational Cohort Studies from South Korea, Japan, and the UK.

Research Background and Purpose

Post-COVID-19 condition refers to cases where symptoms from the infection persist for more than four weeks after the initial infection. These symptoms mainly include fatigue, breathing difficulty, depression, anxiety, and cognitive decline. Research published in The Lancet, a well-known British journal, showed that 45% of COVID-19 patients experienced post-COVID-19 conditions. The frequency of these long-term effects has highlighted the importance of continued research in this area.

The research team at KHU was driven by curiosity about existing beliefs regarding COVID-19 and allergic diseases. Professor Yeon explained, “There is a seesaw relationship between allergic and inflammatory reactions; those with allergic diseases are less likely to contract COVID-19. This led us to wonder if the reverse case might also be true, leading our team to begin the study.”

To explore this question, the team selected four allergic diseases?asthma, rhinitis, atopic dermatitis, and food allergies?and investigated whether COVID-19 infection could contribute to the development of these conditions.

Research Methods and Results

The research team analyzed data from 10 million individuals in South Korea, 12 million in Japan, and 460,000 in the United Kingdom (UK), covering the period from January 1, 2020, to December 31, 2021. The use of big data analysis distinguished this research from other studies. Professor Yeon stated, “It takes a lot of time to get results using traditional methods, such as clinical trials and interviews. It might take 10 times longer to achieve the same results with the same dataset.” He added, “The medical field tends to adhere to conventional approaches, which makes it challenging to promote the widespread use of data analysis. However, with the development of artificial intelligence and the increased urgency brought on by the COVID-19 pandemic, our team was able to utilize data analysis techniques.”

The research team compared the severity and number of allergic disease cases between infected and uninfected groups and discovered that COVID-19 infection increases the risk of developing allergic diseases. The infected group experienced 125% more asthma and 20% more rhinitis than the uninfected group. Furthermore, the team discovered that the severity of COVID-19 symptoms influenced the likelihood of developing allergic diseases. Those with severe or moderate COVID-19 symptoms showed 48% more allergic disease cases, while those with mild symptoms exhibited an 18% increase compared to the uninfected group. Another notable finding was that COVID-19 vaccination reduced the incidence of allergic diseases, with vaccinated individuals showing a 19% lower rate of contraction.

Implications and Future Directions

This study has garnered significant attention in the medical field for challenging existing beliefs. Previous studies suggested that having an allergic disease could prevent COVID-19 infection, leading the medical community to assume that the reverse case would also be true. However, this study demonstrates the opposite: people are more likely to develop allergic diseases after contracting COVID-19. This finding underscores the need to manage allergic diseases as part of post-COVID-19 care.

The study also addressed a controversy regarding race. It is often argued that genetic differences among races could lead to varying results in such studies. To tackle this concern, the research team included a UK cohort in their analysis. The consistent results across different genetic backgrounds demonstrated that these findings are valid globally. Furthermore, this suggests that the international community should take the results seriously and prepare responsive measures, regardless of racial differences.

Based on their findings, the research team proposed two future directions: policy development and individual practices. Given that vaccination can reduce the occurrence of allergic diseases as a post-COVID-19 condition, the team recommended that public policy consider including vaccination as a necessary preventive measure. Additionally, they emphasized that the best way to protect oneself from allergic diseases is to prevent infection in the first place. Therefore, they advised individuals to take personal precautions, such as washing hands regularly and covering noses and mouths while sneezing.

The term endemic is appropriate to describe the current situation, but the risk of the virus remains significant, particularly for elderly groups. According to the Korea Disease Control and Prevention Agency, the number of newly hospitalized patients due to the virus rose significantly, from 226 in the third week of July to 1,357 by the second week of August.

Professor Yeon explained, “COVID-19 has evolved to enhance its ability to spread rather than increase in severity, leading the world to pay less attention to the virus compared to the pandemic era. However, given its high infection rate and impact on the elderly, it is necessary to pay attention to the disease.”

Given the current situation, the research team stated that they are conducting further studies related to COVID-19 using data analysis techniques. Their latest research focuses on the relationship between COVID-19 and a healthy lifestyle, including factors such as smoking, exercise, and alcohol consumption. Additionally, the team plans to study post-COVID-19 conditions based on different virus mutations. They aim to have research results on the original, Delta, and Omicron variants by the first half of next year.