Should breast cancer patients have the Covid-19 vaccine?

Many patients are asking whether it is OK to have the vaccine if you have had breast cancer, and particularly if you are on treatment. From what we know of these vaccines so far the answer for nearly everyone is YES.

Firstly, there is no reason to assume they won’t be effective if you have had breast cancer in the past and are now off all treatment, or if you are on long term hormone-blocking drugs (tamoxifen, aromatase inhibitors and the like).  If you are on chemotherapy or one of the newer targeted therapies such as palbociclib, ribociclib and abemaciclib then we don’t know for sure if the vaccines will be effective but it’s likely they will be. That’s because these targeted drugs mainly suppress neutrophils, a type of white blood cell that fights bacterial infections but is not involved in developing immunity. So if you have a lowered neutrophil count because of your treatment, your body is generally still able to mount an effective immune response to the vaccine. 

The other side of the coin is the safety aspect.  Here, the evidence so far shows that the vaccines currently available are very safe, and any tiny risk of a serious reaction is far outweighed by the risks of catching Covid. One of the reasons they appear to be so safe is because of how they work.

How do Covid-19 vaccines work?

Some vaccines consist of the live virus which has been attenuated (i.e. weakened) so that it can no longer harm the recipient but still has the capacity to stimulate an immune response. These have the very rare but potentially dangerous risk of behaving like an active virus, particularly in someone who is immune -suppressed for whatever reason. So, it’s important to note that the Covid vaccines so far available do NOT work in this way.

The Pfizer-BioNTech vaccine, the first to become available, works using modern technology.  It consists of a strand of the virus’ genetic material, so-called mRNA (m stands for messenger because it carries a message from the genetic code of the virus to make a specific viral protein). This mRNA is injected in the vaccine and taken up by normal cells in the body; these start to make a specific Covid viral protein, the spike protein. This spike is what the virus uses to attach to cells before invading them. It isn’t dangerous on its own because it’s not attached to the virus. It’s enough however to stimulate the body’s immune system to make antibodies which would recognise the same spike protein on any subsequent virus that got into the body and kill it. Clever, isn’t it?

A further advantage of this technology is that any appropriate mRNA can be made quickly, apparently within a week or so, once the viral genetic code has been worked out. So, if a mutant strain were to emerge which was resistant to the current vaccines, a modified effective new vaccine could be produced very quickly.

The Oxford-Astra Zeneca vaccine has also just become available in the UK.  It works in a different way from the Pfizer-BioNTech one. It’s made starting with a common coronavirus (Covid is also a coronavirus) which causes colds in chimpanzees. This virus is known to be harmless to humans but to be doubly sure of its safety it is first of all modified so it can’t even grow in humans, it is then further genetically manipulated so that it carries some of the Covid-19 proteins including the spike protein. These stimulate an immune response involving the production of anti-Covid antibodies which are then ready to kill any Covid virus that subsequently invades the body.  

Are there any patients with breast cancer who should not have the vaccine?

The answer is very few. A couple of patients in the first day or two of the immunisation programme had a rapid onset allergic reactions but they were already prone to severe reactions in the past.  You will be asked about previous allergic reactions when you go to the vaccination centre. But we’re talking about severe reactions here; don’t be put off from going along when you’re called if you’ve had minor reactions in the past; the vaccination team will assess your risk.   

If someone also has an immune-deficiency disorder separate from breast cancer, then it is possible that the vaccination would be ineffective. Advice from their specialist would be required here.

Cancer patients treated with high dose chemotherapy and similar very intensive treatments also have markedly impaired immunity and at present would probably not be appropriate for vaccination. But this treatment is very rarely used in breast cancer because we have other more effective and far fewer toxic therapies.

And finally, some patients with breast cancer are being treated with a new approach called immunotherapy. I’m going to write a blog on this in the near future. Whether or not such patients should have the vaccine is very much under study at present, and each patient needs to discuss this with their specialist teams.

In conclusion

So, to sum up, vaccination at present offers by far the best way out of this terrible Covid-19 pandemic. And it is VERY SAFE. Those who have had breast cancer, just like everyone else, should seize the opportunity to have the vaccine as soon as it is offered to them.

Meanwhile everybody, stay safe!

Ian E Smith

Professor of Cancer Medicine

Royal Marsden Hospital and Institute of Cancer Research, London