Worried about having your second dose of AstraZeneca vaccination?
Published 28 June 2021
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Like all medicines, vaccines can cause side effects. Most of these are mild and short-term, and not everyone gets them.
It is important that you get your 2 doses of the COVID-19 vaccines to give you the best protection. Not all COVID-19 vaccines are the same.
Side effects
Very common side effects in the first day or two include:
- having a painful, heavy feeling and tenderness in the arm where you had your injection
- feeling tired
- headache, aches and chills
The AstraZeneca (AZ) vaccine causes far fewer side effects after the second dose.
Pfizer and Moderna tend to cause more side effects after the second dose. Studies have shown that if you have 1 of these vaccines after a first dose of AZ, your risk of common side effects is higher. Most of these side effects only last a day or two and you still make a good immune response.
Current advice
The current advice from the Joint Committee on Vaccination and Immunisation (JCVI) is:
Those who have received their first dose of AZ vaccine without suffering any serious side effects should continue to be offered the second dose to complete the course. This includes individuals who are aged 39 years or younger.
Rare side effects
Since March 2021 there have been reports from the UK and internationally of a very rare condition of thrombosis (blood clots) and thrombocytopenia (low platelets). In under 50s, around 1 case has been reported for every 50,000 first doses of the AZ vaccine. For the second dose of vaccine, less than 1 case has been reported for every million vaccines given to people under 50 years of age; none of these second-dose cases were confirmed.
The underlying risk factors have not yet been fully established for this condition and a detailed review of suspected cases is ongoing by the Medicines and Healthcare products Regulatory Agency (MHRA), supported by Public Health England (PHE) and other professional groups. This will help us to understand the risk factors for developing this condition. So even if you felt unwell after your dose of AZ vaccine, unless you had this rare clotting event, you are best to complete with this vaccine for your second dose.
It is recommended that you have both doses of the same vaccine. In exceptional circumstances where this is not possible it is better to have a second dose of another vaccine than not at all.
Reporting suspected cases
It is very important that all suspected cases are reported to both the MHRA on the COVID-19 Yellow Card scheme and to PHE’s clinical reporting scheme.
Further information
A blood clotting leaflet for patients receiving their first dose is available.
Further information is available on GOV.UK