COVID-19 vaccine and blood clot risk

Over 20 million doses of the AstraZeneca vaccine have now been administered in the UK. A very rare, but serious, side effect has been reported in a very small number of people receiving this vaccine. This side effect involves the formation of blood clots that that can block veins in the head and can have serious consequences.

Data continues to be collected about how often this side effect occurs, but it is currently believed to occur in just 4 people out of every 1,000,000 having the vaccine. In line with national guidance, we strongly advise all patients, friends, family and staff to have the COVID-19 vaccination.

Recent changes to the national COVID-19 vaccination programme

In light of the recent information regarding the AstraZeneca vaccine and the low risk of blood clots, under 30s will now be offered one of the other licensed COVID-19 vaccinations.


The Joint Committee on Vaccination and Immunisation (JCVI) have recently issued guidance around COVID-19 vaccination and pregnancy. Their advice confirms that the COVID-19 vaccines are safe in pregnancy, and it is preferable for pregnant women in the UK (who meet current criteria for vaccination) to be offered the Pfizer-BioNTech or Moderna vaccines.

Is the COVID-19 vaccine safe?

Before they can be used outside of trials, vaccines have to be approved for use by the MHRA (Medicines Health Regulatory Authority). It is an independent body which assesses the safety of medicines and vaccines to ensure they are safe to use. 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. 

How effective is the COVID-19 vaccine?

The COVID-19 vaccine has been tested in large clinical trials. The results of these trials have shown that the vaccines were safe and effective. The majority of vaccinated people developed protective antibodies against the virus and vaccination significantly reduced the risk of developing symptomatic COVID-19 infection. More information can be found on the MHRA and Public Health England websites. 

Is the COVID-19 vaccine safe for people with cancer?

The JCVI has recently recommended that vaccination is undertaken (first dose at least, ideally both doses) prior to starting chemotherapy. In some circumstances, it might be possible to delay your treatment and you should discuss this with your medical or nursing team. If you are about to start treatment, we will recommend to your GP that you are prioritised for vaccination. 

Our general advice is however that you should go ahead with treatment (surgery, chemotherapy or radiotherapy) when you are called to do so rather than delay.

Is the COVID-19 vaccine effective in people with cancer?

All vaccines (including COVID-19) might be less effective in people receiving chemotherapy due to the impact of the cancer treatment on your immune system. This is very difficult to predict and we recommend that you still go ahead with vaccination if you have had chemotherapy recently or are currently on treatment. We would however advise that this should not be administered on the same day as intravenous chemotherapy in case you react to the vaccine.

Please see guidance from the UK Chemotherapy Board that offers more detailed guidance.

Which COVID-19 vaccines are available?

A number of vaccines are now available in the UK. Which vaccine you have will be determined by a number of factors which include your age and whether you might be pregnant or are considering becoming pregnant. As we learn more about COVID-19 and the vaccines who receives which vaccine may change, but the vaccine centres will make sure that you receive the right vaccine.

Should I have the COVID-19 vaccine, and which vaccine should I have?

We are advising that all our patients receive a COVID-19 vaccine when this is offered. If you are unsure whether you should go ahead, then do discuss this with your specialist team at The Christie.

Are there any known or anticipated side effects?

Like all medicines, vaccines can cause side effects. Most of these are mild and short-term, and not everyone gets them. Even if you do have symptoms after the first dose, you still need to have the second dose. 

Very common side effects include:

  • Having a painful, heavy feeling and tenderness in the arm where you had your injection. This tends to be worst around 1-2 days after the vaccine
  • Feeling tired
  • Headache
  • General aches, or mild flu like symptoms 

As with all vaccines, appropriate treatment and care will be available in case of a rare anaphylactic event following administration. 

Some people are recommended to receive a third primary dose of the COVID-19 vaccine

Latest advice from the Joint Committee on Vaccination and Immunisation (JCVI) recommends that a third dose of the COVID-19 vaccine is given for individuals aged 12 and over who may have been immunosuppressed at the time of their initial COVID-19 vaccines. We will inform you and your GP if you have had treatment at The Christie which means you are eligible for a third dose of COVID-19 vaccine.

Who cannot have the vaccine?

People known to have severe allergic reactions to previous vaccine should not currently be vaccinated. The COVID-19 vaccines do not contain any animal or human products and are safe for people who are allergic to eggs. 

The greenbook (link below) provides useful information regarding the use of the vaccine in women who are pregnant or considering becoming pregnant.

There are a number of factors to be considered given the risks and benefits involved, and this may need to be considered on a case by case basis. 

People who are suffering from a fever-type illness should also postpone having the vaccine until they have recovered. 

Does COVID-19 vaccination mean that other infection control precautions can be avoided?

No, it is important that you also continue to adhere to other infection control guidance such as wearing a mask, hand hygiene and social distancing; this is because the vaccine may be less effective in people with cancer. 

How long does the vaccine take to become effective?

The COVID-19 vaccine will reduce the chance of you suffering from COVID-19 disease. After 14 days you will have a high level of immunity to COVID-19. It is believed that this immunity will last for a number of months, but a second dose will be required to deliver longer term immunity. 

Is the vaccine vegan/vegetarian friendly?

Yes, the Pfizer vaccine does not contain any meat derivatives or porcine products.

If, and when, further vaccines are approved we will publish information about known allergens or ingredients that are important for certain faiths, cultures and beliefs. 

Does COVID-19 vaccination work in all people?

In trials, similar results were seen in all the people who received the vaccine, regardless of their age, gender and state of health. 

What is the evidence to show the vaccine is safe for BAME communities?

The phase three study of the Pfizer BioNTech COVID-19 vaccine demonstrated a vaccine efficacy of 95%, with consistent efficacy across age, gender and ethnicity. Overall, among the participants who received the COVID-19 vaccine 82.1% were White, 9.6% were Black or African American, 26.1% were Hispanic/Latino, 4.3% were Asian and 0.7% were Native American/Alaskan. 

Who is at risk from COVID-19?

The symptoms of COVID-19 caused by infection with the SARS-CoV-2 virus vary widely between individuals. Black, Asian and Minority Ethic people and older adults are at increased risk of more serious infection as are those with underlying health problems such as diabetes, heart disease and cancer. But anyone can contract and transmit the virus. 

I’m currently ill with COVID-19, can I get the vaccine?

People currently unwell and experiencing COVID-19 symptoms should not receive the COVID-19 vaccine until they have recovered. 

Do people who have already had COVID-19 get vaccinated?

Yes, they should get vaccinated. There is no evidence of any safety concerns from vaccinating individuals with a past history of COVID-19 infection, or with detectable COVID-19 antibody, so people who have had COVID-19 disease (whether confirmed or suspected) can still receive the COVID-19 vaccine when it is their time to do so. 

I have had my flu vaccine; do I need the COVID-19 vaccine as well?

The flu vaccine does not protect you from COVID-19. As you are eligible for both vaccines, you should have them both. 

Will the COVID-19 vaccine protect me from flu?

No, the COVID-19 vaccine will not protect you against the flu. If you have been offered a flu vaccine, please try to have this as soon as possible to help protect you, your family and patients from flu this winter. 

If you are a patient, please do feel free to discuss with your clinical team at your next appointment but please do not call The Christie Hotline as this blocks the line for those people requiring urgent medical advice. 

How are the Government raising awareness of the vaccine among the NHS workforce?

The Cabinet Office has developed a campaign to raise awareness of the vaccine with the public and health and social care staff. This includes specific engagement with BAME communities and workforce. 

Why are healthcare workers amongst the first groups to receive the vaccine?

Patient-facing health and social care staff are a priority group because of their heightened risk of exposure to the virus. 

The NHS is experienced in vaccinating hundreds of thousands of staff quickly and safely – we do it every year for the flu vaccine – and all local NHS employers will be responsible for ensuring that 100% of eligible staff have the opportunity to take it up over the coming weeks and months. 

Why is it important to get your COVID-19 vaccination?

Getting your COVID-19 vaccination as soon as you can, should protect you and may help to protect your family and those you care for. 

The COVID-19 vaccine should help reduce the rates of serious illness and save lives and will therefore reduce pressure on the NHS and social care services. 

Is it mandatory and what happens if staff don’t want the vaccine?

No, the COVID-19 vaccine is not mandatory. But it is highly recommended and all eligible staff will be offered the vaccination. We are confident that most staff – as they do every year for the flu vaccine – will protect themselves and their patients by getting the vaccine.  

Will healthcare workers need to pay for the vaccine?

No, the COVID-19 vaccination is only available through the NHS to eligible groups and is a free vaccination. 

Can I go back to work after having my vaccine?

Yes, you should be able to work as long as you feel well. We will ask you to wait for around 10 to 15 minutes after your vaccination to check you are feeling okay. 

Can the vaccine give me the COVID-19 infection?

The vaccine cannot give you COVID-19 infection, and 2 doses will reduce your chance of becoming seriously ill. However, you will need to continue to follow the guidance in your workplace, including wearing the correct personal protection equipment and taking part in any screening programmes. 

How many staff at The Christie have been vaccinated?

Over 3,300 staff at The Christie have now received both doses of the COVID-19 vaccine.

Can staff still receive the vaccine?

Yes. The Trust continues to encourage all staff to be vaccinated and has put in place arrangements for any staff who have not been vaccinated to receive the vaccine at one of the vaccine centres in Manchester.

You can find out further information by reading the greenbook


The Medicines and Healthcare products Agency can confirm that the Pfizer/BioNTech COVID-19 vaccine does not contain any components of animal origin.

A full list of ingredients for the qualitative and quantitative composition of the vaccine can be found at point 2 in the Information for Healthcare Professionals on Pfizer/BioNtech Vaccine.

A full list of ingredients for the excipient composition of the vaccine can be found at point 6 in the Information for Healthcare Professionals on Pfizer/BioNtech Vaccine.

A full list of ingredients for the qualitative and quantitative composition of the vaccine and a full list of the excipient composition of the vaccine can be found at point 6 in the Information for Recipients of the Pfizer/BioNtech Vaccine. 


  • ALC-0315 = (4-hydroxybutyl) azanediyl)bis (hexane-6,1-diyl)bis(2-hexyldecanoate)
  • ALC-0159 = 2-[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide
  • 1,2-Distearoyl-sn-glycero-3-phosphocholine
  • cholesterol
  • potassium chloride
  • potassium dihydrogen phosphate
  • sodium chloride
  • disodium hydrogen phosphate dihydrate
  • sucrose
  • water for injections 

Please see the website for further information.

Last updated: October 2021