Broadly speaking, travellers are not required to take additional vaccinations if you are already vaccinated for the common contagious diseases like measles-mumps-rubella (MMR), diphtheria-tetanus-pertussis, varicella (chickenpox) and polio.
We recommend you to stay up-to-date with your yearly flu vaccination to protect against influenza viruses that will be most common during the upcoming season.
If you wish to take extra pre-caution, you can consider getting vaccine for Hepatitis A and Typhoid. This is because travellers may get these two diseases through consumption of contaminated food or water, though this is rare in Singapore.
Hepatitis B is a contagious virus that is transmitted through blood and other body fluids. Travellers should get vaccine Hepatitis B if one may have sex with a new partner, get a tattoo or piercing, or have a medical procedure.