2.4. Eligibility Criteria
Case report and case series studies on the development of acute abdomen in persons older than 18 years following COVID-19 vaccination were included. Other types of studies such as systematic reviews, narrative reviews, letters to the editor, congress or conference abstracts, editorials, interviews, commentaries, short communications, brief reports, and newspaper articles were excluded. In addition, we excluded records that reported patients younger than 18 years of age and incorrect outcomes (Other type of outcomes). We also excluded records that were not in English, Portuguese, or Spanish.