HeLa cells are extremely potent and can travel through dust in the air. However, I'm not sure that scientists could get infected with HeLa cells if they reached the stomach. The acid in our stomach is very potent and would kill any HeLa cells that reached that point.
However, if a scientist decided to infect him/herself via injection of HeLa cells into his or her arm with a syringe, tumors would appear at the site of infection. But if the scientist is healthy and not already immunosuppressed, his or her own body would reject the HeLa cells and ultimately destroy them.
Hope this helped!
The Immortal Life of Henrietta Lacks, by Rebecca Skloot.