The COVID-19 vaccine booster can cause temporary swelling of lymph nodes, a common and expected side effect. This reaction signals that the body’s immune system is actively building protection against the virus.
The Role of Lymph Nodes in Immune Response
Lymph nodes are small, bean-shaped structures that are part of the lymphatic system, a component of the body’s immune system. They are distributed throughout the body, with notable clusters located in areas such as the neck, armpits, and groin. These nodes act as filters for lymph fluid, a fluid that collects waste products, damaged cells, and foreign substances like bacteria and viruses from tissues.
Inside the lymph nodes, various immune cells, including specific immune cells called lymphocytes, are organized to identify and neutralize threats. When a vaccine is administered, particularly into the arm, components of the vaccine travel to the nearby lymph nodes, such as those in the armpit. Here, immune cells recognize the vaccine components, prompting an immune response. This activation leads to the multiplication and maturation of immune cells within the nodes, causing them to swell temporarily as they prepare to defend the body against the actual virus.
Expected Duration of Swelling After Booster
Swollen lymph nodes following a COVID-19 vaccine booster are a normal indication of an active immune response. This swelling typically appears a few days after vaccination, often in the armpit on the same side as the injection. While individual experiences can vary, this side effect generally resolves within a few days to a few weeks.
Some studies indicate that swelling can persist for a longer duration, with a mean resolution time of around 102 days after a booster dose, and up to 127 days after the first vaccine dose. In some cases, enlarged lymph nodes have been observed to persist for several months. Factors such as the type of vaccine, specifically mRNA vaccines like Pfizer and Moderna, may influence the likelihood and duration of lymph node swelling, with Moderna sometimes associated with longer resolution times compared to Pfizer-BioNTech.
When to Consult a Healthcare Professional
Although swollen lymph nodes after a COVID-19 vaccine booster are generally a normal and temporary sign of immune activation, there are circumstances when consulting a healthcare professional is advisable. If the swelling persists beyond the typical duration of a few weeks, or if it continues to enlarge rather than decrease over time, it warrants medical evaluation. For instance, if the swelling remains noticeable after six weeks, medical advice should be sought.
If the swollen lymph nodes are accompanied by additional concerning symptoms, a medical consultation is important. These symptoms can include increasing pain, redness, or warmth over the swollen area. Other general symptoms that should prompt a visit to a healthcare provider include unexplained weight loss, night sweats, persistent fever unrelated to initial vaccine side effects, or difficulty breathing.