COVID-19 vaccine may cause swelling of local lymph nodes. Does this affect mammogram results?

When you attend breast screening appointments, mammogram, breast ultrasound or other types of cancer screening, it is recommended to mention to your doctor or radiographer that you have had a COVID-19 vaccination recently.

This is because it is quite common for the vaccine to cause swelling of the lymph nodes nearest to the injection-site, such as armpit and neck. This occurs most commonly after the second or booster dose. Swollen lymph nodes (medically called lymphadenopathy) is one of the top ten events reported to Medsafe through the CARM reporting system. 

Swelling of lymph nodes near to the site of injection, in the case of vaccines, or closest to an infection is a normal response when the immune system is stimulated. It usually occurs within one or two days and settles after a few days but can persist for a few weeks and may be detectable on a mammogram or scan for a month or two. In this case, it is advised to monitor such lymph node changes for at least 6 weeks after vaccination. You do not need to delay your vaccination, your mammogram or treatment. 

Click this link for further information from BreastScreen Aotearoa.

See also information about PET CT scans.


Edmonds CE, Zuckerman SP ,Conant EF. Management of unilateral axillary lymphadenopathy detected on breast MRI in the era of coronavirus disease (COVID-19) vaccination. AJR: American Journal of Roentgenology, 2021.

Garreffa E, Hamad A, O'Sullivan CC, et al. Regional lymphadenopathy following COVID-19 vaccination: Literature review and considerations for patient management in breast cancer care. European Journal of Cancer, 2021. 159: p. 38-51.

Medsafe. 2022 Adverse events following immunisation with COVID-19 vaccines: Safety Report #40 – 31 January 2022. online. URL: (accessed 25 February 2022)

Last updated: 28 February 2022