Thanks for your question on Health Care Magic.
I can understand your concern.
The reaction mentioned for the
vaccine are only acute so vaccine is unlikely the cause for her symptoms after 3 years.
Chest tightness as described by you is commonly seen in
asthma. Since her chest x ray is normal, no need to worry for
lung infection.
Possibility of asthma is more in her case.
So better to
consult pulmonologist and get done clinical examination of respiratory system and PFT (Pulmonary Function Test).
PFT is needed for the diagnosis of asthma.
It will also tell you about severity of the disease and treatment of asthma is based on severity only.
She will be better with inhaled bronchodilators and inhaled corticosteroid (ICS).
Don't worry, she will be alright.
Hope I have solved your query. Thanks.