Some women, users of TikTok, have shared videos on the platform claiming that after performing the Pfizer or Moderna vaccine, they have noticed that their breasts are larger.

Experts say that in these cases, we are dealing with lymph node enlargement. In other cases, they may be an early sign of cancer, but in the case of vaccination, there is another explanation that thankfully has nothing to do with cancer.

Vaccines that transmit messenger RNA (mRNA), such as Pfizer and Moderna, provide a small amount of genetic code to guide cells on how to replicate the virus's surface protein, the "spike" protein, which activates the immune system. Lymph nodes contain B cells which use this information to generate antibodies in response to a foreign organism. Accumulation of antibodies in the lymph nodes can result in their expansion.

This may cause the breasts to feel bigger for a short time after the vaccine, but it is not a cause for concern.

Sources: American Cancer Society, American Centers for Disease Control and Prevention