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COVID-19: Original Article
Identifying adverse reactions following COVID-19 vaccination in Korea using data from active surveillance: a text mining approach
Hye Ah Lee, Bomi Park, Chung Ho Kim, Yeonjae Kim, Hyunjin Park, Seunghee Jun, Hyelim Lee, Seunghyun Lewis Kwon, Yesul Heo, Hyungmin Lee, Hyesook Park, COVID-19 Vaccine Safety Research Committee
Epidemiol Health. 2025;47:e2025034.   Published online June 30, 2025
DOI: https://doi.org/10.4178/epih.e2025034
  • 5,947 View
  • 117 Download
AbstractAbstract AbstractSummary PDFSupplementary Material
Abstract
OBJECTIVES
Unstructured text data collected through vaccine safety surveillance systems can identify previously unreported adverse reactions and provide critical information to enhance these systems. This study explored adverse reactions using text data collected through an active surveillance system following coronavirus disease 2019 (COVID-19) vaccination.
METHODS
We performed text mining on 2,608 and 2,054 records from 2 survey seasons (2023-2024 and 2024-2025), in which participants reported health conditions experienced within 7 days of vaccination using free-text responses. Frequency analysis was conducted to identify key terms, followed by subgroup analyses by sex, age, and concomitant influenza vaccination. In addition, semantic network analysis was used to examine terms reported together.
RESULTS
The analysis identified several common (≥1%) adverse events, such as respiratory symptoms, sleep disturbances, lumbago, and indigestion, which had not been frequently noted in prior literature. Moreover, less frequent (≥0.1 to <1.0%) adverse reactions affecting the eyes, ears, and oral cavity were also detected. These adverse reactions did not differ significantly in frequency based on the presence or absence of simultaneous influenza vaccination. Co-occurrence analysis and estimation of correlation coefficients further revealed associations between frequently co-reported symptoms.
CONCLUSIONS
This study utilized text mining to uncover previously unrecognized adverse reactions associated with COVID-19 vaccination, thereby broadening our understanding of the vaccine’s safety profile. The insights obtained may inform future investigations into vaccine-related adverse reactions and improve the processing of text data in surveillance systems.
Summary
Korean summary
* 본 연구는 COVID-19 백신 접종 후 자가 보고된 증상을 텍스트 마이닝으로 분석하여, 이전에 알려지지 않았던 부작용을 확인하였습니다. * 본 연구 결과는 백신 부작용에 대한 이해를 높이고, 향후 연구 및 감시 체계 개선에 중요한 통찰력을 제공합니다.
Key Message
* This study used text mining of self-reported symptoms following COVID-19 vaccination to identify previously unrecognized adverse reactions. * Our findings enhance the understanding of vaccine side effects and provide valuable insights for future research and surveillance system improvement.
COVID-19: Original Article
Barriers to COVID-19 vaccine surveillance: the issue of under-reporting adverse events
Yunha Noh, Hwa Yeon Ko, Ju Hwan Kim, Dongwon Yoon, Young June Choe, Seung-Ah Choe, Jaehun Jung, Ju-Young Shin
Epidemiol Health. 2023;45:e2023054.   Published online June 7, 2023
DOI: https://doi.org/10.4178/epih.e2023054
  • 18,582 View
  • 162 Download
  • 6 Web of Science
  • 7 Crossref
AbstractAbstract AbstractSummary PDFSupplementary Material
Abstract
OBJECTIVES
This study investigated the reporting rates of adverse events following immunization (AEFIs) to the spontaneous reporting system (SRS) and its predictors among individuals with AEFIs after coronavirus disease 2019 (COVID-19) vaccination.
METHODS
A cross-sectional, web-based survey was conducted from December 2, 2021 to December 20, 2021, recruiting participants >14 days after completion of a primary COVID-19 vaccination series. Reporting rates were calculated by dividing the number of participants who reported AEFIs to the SRS by the total number of participants who experienced AEFIs. We estimated adjusted odds ratios (aORs) using multivariate logistic regression to determine factors associated with spontaneous AEFIs reporting.
RESULTS
Among 2,993 participants, 90.9% and 88.7% experienced AEFIs after the first and second vaccine doses, respectively (reporting rates, 11.6 and 12.7%). Furthermore, 3.3% and 4.2% suffered moderate to severe AEFIs, respectively (reporting rates, 50.5 and 50.0%). Spontaneous reporting was more prevalent in female (aOR, 1.54; 95% confidence interval [CI], 1.31 to 1.81); those with moderate to severe AEFIs (aOR, 5.47; 95% CI, 4.45 to 6.73), comorbidities (aOR, 1.31; 95% CI, 1.09 to 1.57), a history of severe allergic reactions (aOR, 2.02; 95% CI, 1.47 to 2.77); and those who had received mRNA-1273 (aOR, 1.25; 95% CI, 1.05 to 1.49) or ChAdOx1 (aOR, 1.62; 95% CI, 1.15 to 2.30) vaccines versus BNT162b2. Reporting was less likely in older individuals (aOR, 0.98; 95% CI, 0.98 to 0.99 per 1-year age increment).
CONCLUSIONS
Spontaneous reporting of AEFIs after COVID-19 vaccination was associated with younger age, female sex, moderate to severe AEFIs, comorbidities, history of allergic reactions, and vaccine type. AEFIs under-reporting should be considered when delivering information to the community and in public health decision-making.
Summary
Korean summary
본 연구는 국내 19-49세 성인을 대상으로, 코로나19 예방 백신 접종 후 이상반응 경험에 대한 자발적 보고율을 조사하고, 자발적 보고와 관련된 요인을 파악하고자 하였다. 2021년 12월 2일부터 20일까지 온라인 설문조사를 통하여 자료를 수집하였으며, 연구대상자는 코로나19 예방 백신의 기초접종을 완료한 후 2주 경과한 19-49세 성인으로, 전국 대표성을 확보하기 위해 성별, 연령, 지역별로 층화하여 모집하였다. 이상반응 자발적 보고율은 1차 접종과 2차 접종 후 각각 약 11.6%, 12.7%로 나타났으며, 중등도에서 중증의 이상반응에 대한 자발적 보고율은 약 50.5%, 50.0%로 나타났다. 이상반응 자발적 보고율 관련 영향요인으로는 젊은 연령층, 여성, 이상반응의 중증도, 동반질환, 알러지 반응 이력, 기초접종 백신 종류가 포함되었다.
Key Message
Spontaneous reporting rates of adverse events following immunization (AEFIs) against coronavirus disease 2019 (COVID-19) were low, at around 12 % of any AEFIs and 50 % of moderate-to-severe AEFIs. Younger age, female sex, severe AEFIs, comorbidities, history of allergic reactions, and the type of COVID-19 vaccine were associated with the AEFIs reporting.

Citations

Citations to this article as recorded by  
  • Enhanced safety surveillance of the adjuvanted respiratory syncytial virus vaccine among Italian older adults
    Alexander Domnich, Andrea Orsi, Piero Luigi Lai, Elvira Massaro, Carlo-Simone Trombetta, Julieta Pastorino, Charlott Roihl, Sara Tardito, Marianna Pianta, Giancarlo Icardi, Donatella Panatto
    Vaccine: X.2025; 24: 100647.     CrossRef
  • Serious adverse drug reactions associated with anti-SARS-CoV-2 vaccines and their reporting trends in the EudraVigilance database
    Wojciech Nazar, Jan Romantowski, Grzegorz Nazar, Marek Niedoszytko, Rüdiger Braun-Dullaeus, Ludmiła Daniłowicz-Szymanowicz
    Scientific Reports.2025;[Epub]     CrossRef
  • Attempts to Infer Observation Bias from Chart Entry Behavior
    Kotonari AOKI, Yosuke NISHIDA, Suguru NOZUE
    Japanese Journal of Pharmacoepidemiology/Yakuzai ekigaku.2025; 30(2): 25.     CrossRef
  • Underreporting of Adverse Events Following COVID-19 Vaccination Among Healthcare Professionals in Poland: Potential Implications for Vaccine Hesitancy
    Jakub Grabowski, Anna Niebrzydowska, Aleksandra Brzozowska, Przemysław Waszak, Paweł Zagożdżon, Shan Ali, Tomasz Brancewicz, Monika Wolff, Aleksandra Macul-Sanewska, Leszek Bidzan
    Tropical Medicine and Infectious Disease.2025; 10(11): 320.     CrossRef
  • Long-term trends in reporting of cardiac adverse drug reactions to COVID-19 vaccines - an exploratory analysis of the EudraVigilance database
    Wojciech Nazar, Jan Romantowski, Grzegorz Nazar, Marek Niedoszytko, Ludmiła Daniłowicz-Szymanowicz
    BMC Infectious Diseases.2025;[Epub]     CrossRef
  • The effect of covid vaccination on menstruation and attitude to the vaccine among Indian women – Results of a prospective survey
    Anbukkani Subbian, Jeevithan Shanmugam, Uma Ram
    Indian Journal of Obstetrics and Gynecology Research.2024; 11(1): 70.     CrossRef
  • Cardiac adverse drug reactions to COVID-19 vaccines. A cross-sectional study based on the Europe-wide data
    Wojciech Nazar, Jan Romantowski, Marek Niedoszytko, Ludmiła Daniłowicz-Szymanowicz
    European Heart Journal - Cardiovascular Pharmacotherapy.2024; 10(7): 599.     CrossRef
Review
Studies on the Association between Phenylpropanolamine (PPA) and Hemorrhagic Stroke in Other Countries.
Seung Mi Lee, Byung Woo Yoon, Byung Joo Park
Korean J Epidemiol. 2004;26(2):1-7.
  • 10,210 View
  • 48 Download
AbstractAbstract PDF
Abstract
OBJECTIVES
Phenylpropanolamine (PPA) had been used widely as cold remedies or appetite suppressants. However, products containing PPA were withdrawn in sequence in the US, Japan, and Korea due to the increased risk of hemorrhagic stroke. The purpose of this paper was to review safety issues related with the PPA use and hemorrhagic stroke in view of pharmacoepidemiology and pharmacovigilance.
METHODS
AND MATERIALS: Researches conducted for evaluating the association between the PPA use and hemorrhagic stroke in other countries were reviewed, which involved case reports, case series, case-control studies, and cohort studies.
RESULTS
In terms of pharmacologic and clinical features, PPA may increase the risk of hemorrhagic stroke through increased blood pressure, heart rate, or vasculitis. The association between the PPA use and hemorrhagic stroke among young women was suggested by case reports from spontaneous adverse events reporting systems or medical journals. The cohort study, using the large prescription database in the US and published in 1984, failed to reveal the association in the population aged below 65. The case-control study conducted as the Yale Hemorrhagic Stroke Project, published in 2000, was the first study to find the association between the PPA as appetite suppressants and hemorrhagic stroke among women ages 18-49 years by well-designed analytic epidemiological research. It led to withdrawal of all products containing PPA in the US and many other countries since 2000. However, the association between PPA and cerebral hemorrhage could not be confirmed by the case-control study conducted in Mexico due to inappropriate recruitment of control group.
CONCLUSIONS
During several years case reports have suggested that hemorrhagic stroke could be induced by PPA, and the Yale Hemorrhagic Stroke Project revealed the association by case-control study and provided a useful model for pharmacovigilance. Nevertheless, their finding could not be applied to other population such as elderly women and male population. And they could not provide any evidence on the association between PPA and stroke when PPA was used as cold remedy taken daily dose below 100mg.
Summary
Epidemiol Health : Epidemiology and Health
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