The UK vaccine programme has been in place for several months now and more than 20 million people have been vaccinated. The Government is aiming to vaccinate all of the top nine priority groups by the end of April, before vaccinating the rest of the adult population by the end of July.
To date, three Covid vaccines have been approved for use in the UK from Pfizer/BioNTech, Oxford/AstraZeneca and Moderna.
The UK has ordered 100 million doses of the AstraZeneca vaccine and it is easier to transport and store than the Pfizer vaccine.
So many of the people already vaccinated in the UK will have received a AstraZeneca vaccine.
Over the coming months, further vaccines are expected to be approved for use in the UK if they pass safety and efficacy checks.
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Data released last month also showed the AstraZeneca vaccine prevents 100 percent of hospitalisations 22 days after an immune response has developed following the first vaccine dose.
The study also found one dose is 76 percent effective in preventing infection between 22 and 90 days after the first vaccine is administered.
When a second vaccine dose is given after this stage, the AstraZeneca vaccine is found to be 82.4 percent effective.
Ongoing research is looking into how effective existing vaccines are against new variants of COVID-19.
Can you choose which vaccine you have?
People cannot choose which Covid vaccine they are given.
So it is important someone takes the vaccine they have been offered when it is their turn to have a vaccine.
The vaccines offered at different vaccination centres will depend on supply and distribution.
When someone returns to a vaccine centre for their second vaccine dose, it is recommended they are given the same vaccine as they received for the first dose.
In some exceptional circumstances, the person may receive a different vaccine for their second dose, such as if there is no record of what vaccine they were first given.
If someone has any medical concerns about a vaccine, or they have any history of serious allergic reaction, they should discuss this with healthcare staff before getting vaccinated.
Vaccines are being administered based on the priority list outlined by the Joint Committee on Vaccination and Immunisation (JCVI).