Swollen lymph nodes after 3 doses of Covid-19 vaccine – VnExpress

Some of my friends have swollen lymph nodes after receiving the 3rd dose of Covid-19 vaccine, please ask the doctor why and is this reaction dangerous? (Van Dung, 35 years old, HCMC)


Compared with the first and second doses of Covid-19 vaccine, the percentage of people with lymphadenopathy after vaccination with Covid-19 vaccine is higher due to the increased cellular immune response. Specifically, the Covid-19 vaccine, after entering the body, will stimulate the response of helper T cells, increasing the response of the germinal centers of nearby B lymphocytes, leading to the proliferation of lymph nodes near the injection site.

In addition, compared with other vaccines, research shows that vaccines using mRNA technology will produce these reactions more strongly, so the rate of lymph node swelling after injection is also higher.

Depending on each person’s response, there will be different side effects. In people with lymphadenopathy, the lymph nodes usually appear 2-5 days after the injection, the lymph node site is near the injection site. These nodes may last for more than 6 weeks. You should not be too worried but need to monitor the status of the lymph nodes, see if they are red, swollen, and far from the injection site. In case the lymph nodes are still not recessive after 12 weeks, go to the doctor for examination and screening.

Medical staff prepare dose of Pfizer vaccine on October 27, 2021. Photo: Quynh Tran

Doctor, Doctor Nguyen Huy Luan
Head of Immunization Unit, Ho Chi Minh City University of Medicine and Pharmacy Hospital


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