My kid aged 4 got in contact with a blood cancer patient whose undergoing chemo. they used the same washroom where the chemo patient had vomited right after chemo and they were also kissed by the patient . what will happen if the chemo is transferred?

The chemo does not transfer. The only risk to the kid are transfer of common germs the patient has in their saliva.

There is no risk of chemo transfer. Have a healthy diet, exercise 30 minutes/day, drink plenty of water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. For nutrition: http://www.choosemyplate.gov/. Get HPV and Covid vaccines. Wish you good health!