Background Previous studies have shown that hypothyroidism may have an impact on blood coagulation. However, how hypothyroidism and thyroxine replacement therapy (TRT) affect the risk of venous thromboembolism (VTE) remains controversial. This study aimed to examine the associations of hypothyroidism and TRT with VTE risks. Materials and Methods This nationwide population-based cohort study was conducted using Taiwan's National Health Insurance Research Database. We enrolled 10,818 hypothyroid patients (the exposed cohort) and 21,636 non-hypothyroid subjects (the unexposed cohort) between 2001 and 2014 after 1:2 exact matching according to age, sex, and index year. Hypothyroid patients were further divided into two groups depending on whether they received TRT or not. Adjusted hazard ratios (aHRs) for VTE were calculated using Fine and Gray competing risk models. Results The mean follow-up period was 7.5 years. Hypothyroidism was significantly associated with a higher risk of VTE (aHR = 1.83 [95% confidence interval [CI]: 1.44–2.33, p < 0.001]). Among hypothyroid patients, the TRT subgroup had a non-significant trend of lower VTE risk than the non-TRT subgroup (aHR = 0.73 [95% CI: 0.52–1.01, p = 0.058]). The analysis for individual events revealed a significant association between TRT use and a lower risk of pulmonary embolism among hypothyroid patients (aHR = 0.34 [95% CI: 0.13–0.88, p = 0.026]). Conclusion The data suggest that hypothyroidism was significantly associated with an increased risk of VTE. Among hypothyroid patients, a non-significant trend of lower VTE risk in patients treated with TRT was observed. Further prospective studies or clinical trials are necessary to confirm causality.

Due to COVID-19, people’s lives have changed greatly. In accordance with former experience, an efficacious vaccine is the most effective way to curb the pandemic; thus, many researchers have published related publications in the short term. Hence, this study aims at using bibliometric analysis and visualization to document research trends regarding COVID-19 vaccines, and offer some directions and suggestions for future research. Initially, all eligible publications were downloaded from Web of Science on 1 January 2022. Subsequently, some publications published before December 2019 were removed since COVID-19 did not occur before that date. Finally, Microsoft Excel is used for bibliometric analysis to analyze publication date, author, affiliation, country, publication title, publisher, research area, document type, and language, and visualized software (VOSviewer) is used to visualize author, affiliation, country, and keywords. After analyzing a total of 17,392 publications, the results show that the overall research trend was upward. Moreover, the prominent authors, institutions, and countries inclined towards regional cooperation instead of international cooperation. Furthermore, the most popular research areas were immunology and medicine (general and internal). Ultimately, COVID-19, vaccine, and SARS-CoV-2 were the top 3 keywords. In conclusion, this study shows the approximate research trend for COVID-19 vaccine during the completely first two years of the pandemic. The research focuses moved from safety, effectiveness, and immunology at the early stage to the optimal allocation strategies for COVID-19 vaccine, and eventually to public attitudes and acceptance towards COVID-19 vaccination.

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