Preparation of patient-facing materials of a complex topic, such as describing new vaccines for COVID-19, is difficult to accomplish. This study examined the readability of patient information leaflets accompanying approved COVID-19 vaccines. Readability of patient-facing literature by the medicines regulator in the United States and the United Kingdom describing the recently US (FDA) and UK (MHRA) COVID-19 approved vaccines (Pfizer/BioNTech, AstraZeneca, Moderna) was assessed employing 10 metrics. Analyses showed that showed that this material had a Flesch Ease of Reading score of 53.5 and 54, respectively and a Flesch-Kincaid reading age of between 7th and 8th Grade (12-13 year olds) and between 8th and 9th Grade (13-14 year olds), respectively. When compared to a recent study on COVID-19 information on healthcare websites, the vaccine literature readability was favourable. Adoption of readability calculators and scrutiny of materials of their readability will help authors develop materials with improved understanding for COVID-19 vaccine recipients, carers and family, potentially leading to improved health literacy and vaccine uptake.