Some TikTok and Twitter users have claimed their breasts and lymph nodes (small, bean-shaped structures which contain immune cells) near the injection site had become swollen post-vaccination. The side effect was dubbed by some as the 'Pfizer boob job'.
Silly social media name aside, there is potential that a person’s lymph nodes will swell in one armpit (the side the injection was given) following the Pfizer Covid-19 vaccine.
Lymphadenopathy (swelling of lymph nodes) is a known adverse event of the Moderna and Pfizer/BioNTech Covid-19 vaccines. Research estimates it occurs in 11.6 percent of people receiving their first dose and 16 percent of people receiving their second dose.
As of July 3, New Zealand's Centre for Adverse Events Monitoring (CARM), had received 25 reports of lymphadenopathy in people who had received the Covid-19 vaccine.
When people have vaccines in their upper arm, it’s normal for the lymph nodes in the armpit on that side of the body to be activated and swell. This is part of the body preparing its immune response.
The swelling is usually mild and settles within a few days to weeks, but understandably, can be alarming for people with a personal or family history of breast cancer, or those who carry the BRCA gene mutation.
This is because it can mimic a cancer symptom: during breast screening, a swollen lymph node can look like cancer that has spread (metastasised) from the breast to the lymph node.
The potential for lymph nodes to swell after vaccination prompted some researchers and advocates in the UK and the US to state breast cancer screening appointments should be scheduled to avoid false positives: either before people with breasts receive a first dose of Covid-19 vaccine, or four to six weeks after the second dose when possible.
Breast Cancer Foundation NZ disagrees, and instead urges people not to delay their mammograms, as the potential risk of missing screening outweighs the benefits.
So can the vaccine make your breasts bigger?
In short: no. There's no biological rationale and no prior evidence from other vaccines that would support a connection between breast size and getting a vaccination. While some people report having lymph node swelling, it is doubtful the breast itself - and both breasts - would be swollen from the vaccine.
If you are concerned about a lump in one part of your breast, you should see your GP, regardless of whether or not you have had your Covid-19 vaccination.
It is important not to ignore a lump or other changes, and to stay up to date with mammograms.
Breast Cancer Foundation NZ’s message is this: “If you’re in line for the jab, get it. If you’re in line for a mammogram, get it.”
Just be sure to let your radiologist know if you have had the vaccine, when, and on what side.
Reporting disclosure statement: This post was written with expert advice from Breast Cancer Foundation New Zealand medical adviser and director of Breast Institute NZ, Dr Monica Saini. It was reviewed by Dr Fran Priddy, clinical director of the Vaccine Alliance Aotearoa New Zealand at the Malaghan Institute.
