PUBLISHED ON: 11 March 2021

We answer some common questions about the current coronavirus vaccines and if they are safe and effective for people with breast cancer. Updated 22 December 2021.

Woman having a coronavirus jab

Is the coronavirus vaccine safe if I’m having breast cancer treatment?

For most people, it’s much safer to have the vaccine than not to have it and risk catching coronavirus.

There are three available Covid-19 vaccines, which are considered safe for people having treatments that can weaken the immune system, such as chemotherapy.

Many people will already have had two vaccines, and some cancer patients will be offered a third Covid-19 vaccine (and may also be offered a booster vaccine three months after the third primary vaccination). Your treatment team or GP will let you know if you would potentially benefit from a third vaccine. This is not the same as a Covid-19 vaccine booster.

Can I have the vaccine if I’m taking hormone therapy?

Hormone therapy, such as tamoxifen, letrozole, anastrozole or exemestane, does not typically affect your immune system. Therefore, it shouldn’t reduce the effectiveness of the vaccine, and it should be safe to have the vaccine if you’re taking one of these treatments.

Some people have asked if it’s safe to have the AstraZeneca vaccine if they are on hormone therapy. This follows news stories about a rare type of blood clot in a small number of people who had this vaccine. Blood clots can be a side effect of tamoxifen.

However, as far as we’re aware there’s no increased risk of blood clots in people who have the AstraZeneca vaccine while taking hormone therapy. 

Will the vaccine be effective if I’m having treatment?

Although we don’t know for certain how effective the vaccine will be for people having treatments such as chemotherapy or targeted cancer therapies, it’s likely to still offer some protection against the virus.

During treatment you will usually have regular blood tests to check your white blood cell count. A reduced white blood cell count may mean you’re more at risk of infection.

However, it doesn’t mean that your body is less capable of developing immunity from the vaccine. This is because different parts of the immune system are involved in this process.

You may be advised to have the vaccine at a specific point during your treatment cycle when your immune system is at its healthiest.

A very small study has suggested some cancer patients had less protection after their first dose of the Pfizer vaccine compared to people without cancer.

People with cancer are advised to follow their doctors’ advice about having the vaccine.

Will I be offered a Covid-19 booster vaccine? 

A Covid-19 booster vaccine will be offered to all people in the UK over 18.

This is because it's likely the protection from the original vaccines against severe Covid-19 decreases gradually over time. Having a booster vaccine may help prolong that protection. 

You can read a guide to booster vaccination on the GOV.UK website.

Cancer Research UK has the latest updates on Covid-19 vaccines and cancer.    

Will I be offered a third Covid-19 vaccine?

A third primary Covid-19 vaccine will be offered to people with a severely weakened immune system.

This is because some people may have received less protection against the virus from their original two doses of the vaccine.

It's likely people who were having chemotherapy, or who had received chemotherapy in the previous six months, will be eligible for the third vaccine. It will usually be given at least eight weeks after the second Covid-19 vaccine.

Anyone who is eligible for a third vaccine will be told by their GP or treatment team.

This is a separate plan from the general Covid-19 vaccination booster programme (see above). However, you may be offered a booster three months after your third primary Covid-19 vaccine.

You can find more information about third dose vaccination on the GOV.UK website.

If I am having treatment when should I have a vaccine?

If you are having treatment, when you have your Covid-19 vaccination may depend on the type and timing of your cancer treatment.  Your treatment team will be able to offer advice based on your individual situation.

Can I have a Covid-19 vaccine if I’ve finished my breast cancer treatment?

Yes. When you have completed your breast cancer treatment, your immune system gradually recovers from any side effects of chemotherapy or other treatments. There’s no reason to think the vaccine won’t be effective if you have had breast cancer and have finished your treatment.

What should I do after I’ve had the vaccine?

People considered to be clinically extremely vulnerable, which may be the case if you’re having or have recently completed treatment, may want to take extra precautions.

This may include limiting close contact with people you do not usually meet.

While the vaccine is expected to offer some protection against the virus, we don’t yet know what that level is, especially if your immune system is weakened by cancer treatments. This is a precautionary measure to keep you as safe as possible.

Some people report swelling in the armpit or to the lymph nodes under the arm after a COVID-19 booster vaccination. This seems to be more common with the Moderna booster vaccination. If you notice any swelling following your booster vaccination, it should disappear within about 10 days, if not, or you have any concerns, contact your GP or treatment team.

I have had lymph nodes removed as part of my surgery, can I still have the vaccine?

If you have had surgery to remove some of or all of your lymph nodes in your armpit, you may be worried that having the vaccination will increase your risk of lymphoedema

There’s no strong evidence that having injections in your ‘at risk’ arm will cause lymphoedema. However, you may prefer to use your other arm.

If you have had lymph nodes removed from both sides, the vaccine can be given safely into your thigh.

You’ll need to talk to the vaccination team on the day of your appointment if you’re worried about having an injection on your affected side.


If you have questions about COVID-19 vaccinations and breast cancer, contact our Helpline team on 0808 800 6000.

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