Warning: People vaccinated against COVID-19 may…b/ See more

Some vaccines contain purified viral proteins rather than genetic material, using more traditional vaccine technology.

How Vaccine Safety Was Monitored
Approval was only the beginning.

Health authorities around the world established extensive monitoring systems where doctors, researchers, hospitals, and patients could report possible side effects.

As hundreds of millions of doses were administered, scientists were able to identify even extremely rare adverse events that were impossible to detect during clinical trials.

Common Side Effects
Most reported side effects were mild and temporary, including:

Pain at the injection site
Fatigue
Headache
Fever
Muscle aches
Chills
Swollen lymph nodes
These symptoms generally disappeared within one to three days and reflected the body’s normal immune response.

Rare but Serious Side Effects
Myocarditis and Pericarditis
Rare cases of heart inflammation were observed, particularly among younger males after receiving mRNA vaccines.

Most patients recovered fully with medical treatment and rest.

Blood Clotting Disorders (TTS)
Very rare clotting disorders were linked primarily to adenovirus-vector vaccines, leading some countries to update vaccine recommendations.

Guillain-Barré Syndrome
A small increase in Guillain-Barré syndrome was reported following certain adenovirus-vector vaccines, although the condition remained uncommon.

Severe Allergic Reactions
Anaphylaxis occurred only in extremely rare cases, which is why vaccination centers monitored patients after receiving their doses.