Why are my lymph nodes swollen and sore after a Pfizer or Moderna COVID booster vaccine?

Summary

It's not uncommon to suffer no after-effects following a first, or even second, mRNA vaccine. However, some people complain of sore and swollen lymph nodes after their booster. Key points:

• Following a Pfizer or Moderna COVID booster vaccine, many people report sore and swollen lymph nodes.

• Lymph nodes (or lymph glands) are small bean-shaped lumps of tissue found throughout your body and connected in a network by lymph vessels. 

• They help your body fight off infections and play a vital role in generating immunity via vaccines.

• The most commonly reported adverse event following a COVID booster is swollen or painful lymph nodes.

• Swollen or sore lymph nodes are simply a sign your immune system is being stimulated.

• Clinical trials show up to one in 20 (Pfizer), and one in 10 people (Moderna) will get swollen or sore lymph nodes following their booster shot. That's in contrast to less than one in 100 after their first or second shot.

• The condition is a normal response caused by immune cells that are activated by the vaccine.

According to the Royal Australian College of General Practitioners, although engorged lymph nodes may look and feel confronting, they usually start subsiding after a week or so.

References

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References from the Web:

• Oct 2021 Don't panic if you get swollen lymph nodes after a vaccine booster. But be aware if you're due for a mammogram, doctors say—CNN

• Nov 2021 Here are the side effects you can expect from a COVID-19 vaccine booster shot—Fortune

• Dec 2021 What Causes Armpit Pain after COVID Vaccine in Some People?—Newsweek  

Source Information:

• Article Source: ABC News (Australian Broadcasting Corporation)

• Media Check: ABC News - Media Bias Fact Check (mediabiasfactcheck.com)  (sources link)

• Learning Outcomes: RUNWAY Topics, Learning Outcomes | The Runway (airforce.gov.au)