The lump on a cat’s neck that persists after being vaccinated is usually caused by allergies. You can use a hot towel to apply heat for a while. If it does not disappear within three days, and the lump expands or there is secretion coming out, it is best to take it with you. Cats should go to the pet hospital for examination and treatment to avoid life-threatening injuries.
Tips:
Be sure to choose a regular pet hospital when taking your cat to get vaccinated. Do not buy vaccines online at will to avoid buying fake vaccines.