Since we are not medical professionals, we cannot offer you medical advice. This is definitely a question for your son's provider, who has access to his complete medical history.

The CDC is studying whether one or more of the vaccines may cause myocarditis in certain individuals. It is very rare, both with and without the vaccine an because they have only very recently begun vaccinating young people, and don't have enough data yet to make a firm statement.

As to the question of whether the Covid vaccine makes the blood thicker, no, it provokes an immune response in the body to create antibodies against the Covid virus. That said, myocarditis is caused by an inflammation of the heart muscle, not by thicker blood.

Sue