The COVID-19 vaccine side effect that has been confused with breast cancer

Catriona Harvey-Jenner
·5-min read

From Cosmopolitan

As we know, the COVID vaccine roll out is now in full swing in the UK, and as the weeks progress, younger adults are being invited to get their first dose of the vaccination which will protect them against coronavirus. But as with many vaccines, there can be side effects, and according to data from initial clinical trials, one vaccine in particular is known to yield symptoms that may easily be confused with breast cancer in women.

In a bid to ensure nobody is unnecessarily scared, we spoke to a cancer specialist to break down exactly why the side effect can occur after the vaccine and what it means. The symptom in question is known as 'lymphadenopathy' which is more commonly known as swollen lymph nodes. In clinical trials, it was found to be present in around 11% of people who received the Moderna vaccine after their first dose and 16% after their second dose in the trials. The Moderna vaccine is not yet available in the UK - currently only the Pfizer/BioNTech and the Oxford/AstraZeneca are in use here - but it is said to be rolling out in spring, so could come any time in the next few weeks.

The bottom line is that if you notice lymphadenopathy as a result of the Moderna vaccine, you don't need to worry. It's a known side effect, and you should simply monitor your body for a few weeks to ensure you don't notice any other changes that may also be in line with breast cancer. Here, Dr Penny Kechagioglou, Chief Medical Officer and Clinical Oncologist specialising in Breast at GenesisCare, explains everything you should know about swollen lymph nodes in relation to breast cancer, and why they can also occur as a side effect of the COVID-19 vaccine.

What is lymphadenopathy?

"Lymphadenopathy means swelling of the lymph nodes, which are oval-shaped organs around our body and part of our immune system which fights infections," says Dr Kechagioglou. "Lymph nodes can be found in our neck, in our underarm areas and in our groins, all areas that we can feel. They also exist inside our bodies and next to our organs, where we are not able to feel. The most common cause of lymphadenopathy is infection, such as a sore throat, and lymph nodes usually feel tender when this happens. Other causes of lymphadenopathy includes cancer, medications and autoimmune diseases," she explains.

Photo credit: Tharakorn - Getty Images
Photo credit: Tharakorn - Getty Images

Why can swollen lymph nodes be a symptom of breast cancer?

"Breast cancer can cause swollen lymph nodes under the arm or the neck usually on the same side as the cancer, but sometimes could be the opposite side. The lymph nodes tend to swell either because breast cancer cells have gone inside them, or because they over-produce immune cells to fight the breast cancer," says the oncologist. "If breast cancer has spread to the lymph nodes, the nodes usually feel hard and painless, unlike when they are infected. If multiple underarm nodes are affected with cancer, patients may experience swelling in the arm and/or hand (lymphoedema) on the same side as the cancer."

How common is lymphadenopathy as a symptom of breast cancer?

We're pretty clued up on the most common symptoms of breast cancer: a breast lump or swelling in the breast, breast pain, sudden change in breast shape or nipple inversion. But lymphadenopathy can be another indicator. "Swollen underarm lymph nodes without breast symptoms or signs is not a very common breast cancer presentation, but it can happen," advises Dr Kechagioglou. "If lymphadenopathy is felt, especially if hard and painless, it should not be ignored and urgent specialist advice should be sought."

Why can swollen lymph nodes occur as a side effect of a COVID vaccine?

First and foremost, the oncologist explains that lymphadenopathy in the underarm or neck area on the same side as the COVID vaccine injection is "a normal reaction of the body in the area of the injection". This is because your lymph nodes are "attempting to fight potential infection" that your body has been exposed to as a result of the jab. The doctor clarifies, however, that it doesn't happen to everyone after a COVID vaccination. "In addition, some people may feel the swollen nodes but others not, and only be detected when people have their screening mammograms," she says. [Note: mammograms are only routinely available to over 50s, so it's not something many young women will experience.]

What should you do if you notice swollen lymph nodes after a COVID vaccine?

"If patients feel swollen underarm lymph nodes after COVID vaccination and there are no other symptoms or signs of breast cancer as described above, then they need to monitor their nodes for few days/weeks to see whether they return back to normal," advises Dr Kechagioglou. "If the lymph swelling subsides, then there is nothing more people need to do," she adds. "However, if the nodes don’t return back to normal size in a few weeks, if the nodes become bigger and harder in the meantime or if people have any other symptoms or signs of breast cancer, they should seek urgent medical advice." The oncologist added that it's wise for anyone with a breast screening coming up to postpone it until few weeks after COVID vaccination in order to avoid unnecessary recall due to vaccination-induced lymphadenopathy.

The information in this story is accurate as of the publication date. While we are attempting to keep our content as up-to-date as possible, the situation surrounding the coronavirus pandemic continues to develop rapidly, so it's possible that some information and recommendations may have changed since publishing. For any concerns and latest advice, visit the World Health Organisation. If you're in the UK, the National Health Service can also provide useful information and support, while US users can contact the Center for Disease Control and Prevention.

The latest issue of Cosmopolitan UK is out now and you can SUBSCRIBE HERE.

Like this article? Sign up to our newsletter to get more articles like this delivered straight to your inbox.


You Might Also Like