![A student on the campus of the University of Santiago de Compostela in northwestern Spain.](https://imagenes.elpais.com/resizer/v2/VXVQWNIK3RC4BO4XCR3BWFO6B4.jpg?auth=7375b3b4b0ad1a82ee097dfd3f8c9f4a27535ab80c734da80578c248544dbb57&width=414&height=233&focal=932%2C403)
Smoking is the factor that most alters our defenses, even years after quitting
An experiment with 1,000 people from the same city that began over a decade ago reveals the unknown persistent effects of tobacco on our immune responses
An experiment with 1,000 people from the same city that began over a decade ago reveals the unknown persistent effects of tobacco on our immune responses