Inflammation of the heart muscle is known as myocarditis, while inflammation of the outside of the heart is called pericarditis.
Heart inflammation can result in breathlessness, palpitations, or chest pain, which requires medical attention.
“If you get any side effects, talk to your doctor, pharmacist or nurse,” the MHRA advised.
Most side effects go away within a few days of appearing, the MHRA added, but there are certain responses that require “urgent medical attention”.