In a small number of people, an unexpected side effect of the COVID-19 vaccine has emerged: swollen lymph nodes on the same side of the body as the shot was given. For women who undergo breast screening soon after vaccination, such swelling can show up on a mammogram, so clinicians may need to take extra steps to educate patients about this possibility and assess the need for follow-up testing.
As COVID-19 vaccines are administered, an unexpected side effect has emerged in a small number of people: swollen lymph nodes on the same side of the body as the shot was given. For women who undergo breast screening soon after vaccination, such swelling can appear on a mammogram, requiring clinicians to take extra steps to educate patients about this possibility and assess the need for follow-up testing.
As the first healthcare providers were vaccinated in late 2020 and early 2021, radiologists began seeing instances of enlarged lymph nodes on the same side of the body as the shot. “That was interesting for us all to stop and say, ‘OK, how can we manage this?’” says Constance Lehman, MD, PhD, chief of breast imaging at Massachusetts General Hospital (MGH) in Boston. In response, Lehman and her colleagues published pragmatic advice for handling breast imaging in recently vaccinated women (Am J Roentgenol 2021 Feb 22 [Epub ahead of print]).
“We have two guiding principles: We don't want women to stop getting vaccinated, and we don't want to send a message that they shouldn't be getting their mammogram,” Lehman says.
At MGH, women undergoing a routine mammogram are asked for their dates of vaccination and in which arm their shot was given. If an average-risk woman has had a vaccine within the past 6 to 8 weeks and has swollen lymph nodes on the same side that the shot was given but no other signs or symptoms of cancer, she does not necessarily need to undergo follow-up testing.
“We have a very, very narrowly defined subgroup that we feel comfortable following clinically,” Lehman says. This wait-and-see approach does not apply to women who have or had breast cancer, or those with swollen lymph nodes on the opposite side from the vaccination, who have a suspicious finding in their breast on a mammogram, or who were vaccinated more than 8 weeks ago.
Some centers, Lehman adds, have recommended that women wait to be vaccinated until 8 weeks after breast screening, an approach that makes sense if vaccines and mammography are easily accessible. “Those types of timing intervals are really based on the local environment. I just encourage people to use courtesy and common sense that fits with local resources,” she says.
More data could inform clinical practice. “We're very curious what percentage of our screening patients show these enlarged lymph nodes,” Lehman says, as well as how often lymph node swelling related to the vaccine occurs in women diagnosed with breast cancer. Moreover, she wants to know whether more lymph node biopsies are being done due to vaccine-related swelling—and what proportion of these biopsies are negative. Previous vaccines haven't had such a dramatic impact on the lymph nodes, she adds, but “this might be a new normal for vaccinations.” –Catherine Caruso