How the COVID-19 vaccines were developed

What is a vaccine?

Vaccines teach your immune system how to create antibodies that protect you from diseases. It’s much safer for your immune system to learn this through vaccination than by catching the diseases and treating them. Vaccines are a crucial part of our defence against infectious diseases – like flu and measles – they help to reduce the spread of infectious diseases and even get rid of some altogether.

Once your immune system knows how to fight a disease, it can often protect you for many years.

Since they were introduced, serious conditions like polio and tetanus have become very rare in the UK. Vaccines go through several stages of lab tests and clinical trials before they can be approved for use.

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Who have the vaccines been trialled on? 

Both vaccines approved for use in the UK have been trialled on a variety of people from different backgrounds. This includes men and women of various ages and ethnicities, and those with underlying health conditions.

Further information on the vaccine trials can be found here:

How were the vaccines developed so quickly? 

The vaccines have been developed and trialled in the same way as other medicines and vaccines available in the UK but there are a number of reasons why they have been developed quickly compared to other medicines:

  • The different phases of the vaccine trial were run at the same time, rather than one after the other, which sped up the clinical process.
  • Data from the trials was shared with the MHRA as soon as it was available, rather than waiting until the end.
  • Funding for all of the trials was available at every stage, so there were no delays often caused by seeking funding to continue.
  • Thousands of people were recruited to take part in the clinical trial very quickly, as it was a global effort and many people wanted to volunteer.


How do I know the vaccines are safe?

The vaccines approved for use in the UK have met strict standards of safety, quality and effectiveness set out by the independent Medicines and Healthcare products Regulatory Agency (MHRA).

Any coronavirus vaccine that is approved must go through all the clinical trials and safety checks all other licensed medicines go through.

The vaccines were trialled in the same way as other medicines and vaccines available in the UK. The COVID-19 vaccine trials involved tens of thousands of people from a range of backgrounds to ensure that they are safe for everyone.

So far, millions of people have been given a COVID-19 vaccine and reports of serious side effects, such as allergic reactions, have been very rare. No long-term complications have been reported.

For more information, visit or the MHRA.

What ingredients are in the vaccines?  

Vaccines only contain ingredients that are essential to make them safe and effective. Any ingredients with potential to cause harm, for example, an allergic reaction, are listed even if present in such small amounts. The approved COVID-19 vaccines do not contain any animal, meat or egg products, nor do they contain any material of foetal origin.

The Pfizer/BioNTech vaccine does not contain any alcohol. The Oxford/AstraZeneca vaccine contains a very small amount of alcohol (ethanol), which is less than what is found in natural foods or bread. This is not enough to cause any noticeable effects.

The vaccine ingredients for both vaccines approved in the UK can be found here: