As with any medicine, vaccines are highly regulated products. There are checks at every stage in the development and manufacturing process, and continued monitoring once it has been authorised and is being used in the wider population.
Each of the vaccines are tested on tens of thousands of people across the world. They are tested on both men and women, on people from different ethnic backgrounds, and of all age groups.
Latest data from UKHSA show that six months after receiving a second dose, two doses provide between 55% and 70% protection from needing to be hospitalised for Covid-19. This remains around 70% six months after receiving the booster.