The National Health Service (NHS) is the biggest employer in the UK. The NHS employed over 1.3 million people as January 2021. The NHS is funded directly by taxes and is the fifth largest employer in the world according to an article and one out every 20 employees in the UK works for the NHS.
Source: NHS
The healthcare industry in the US employs more people than the NHS due to the size of the US population. According to a 2018 study, there were 20 million workers in the healthcare industry. Some of the best high-paying jobs are found in this industry. Examples include doctors, nurses, pharmacists, etc.