All viruses – including SARS-CoV-2, the virus that causes COVID-19 – evolve over time. When a virus replicates or makes copies of itself, it sometimes changes a little bit, which is normal for a virus. These changes are called ‘mutations’ or variants.

The dominant variant of the virus currently in the UK is the Delta variant (the variant first identified in India), also known as the B.1.617.2 variant. This means that most people in the UK catching COVID-19, are catching this variant.

Some variants have emerged since the COVID-19 vaccines were developed and tested. The vaccines that are currently in use, or have been approved are expected to provide at least some protection against new virus variants, and are highly effective against the Delta variant after 2 doses. Therefore, changes or mutations in the virus should not make vaccines completely ineffective.

Learn more about the effects of the virus variants on Covid-19 vaccines here