The term 'successfully vaccinated' can be summarized as having achieved immunity from a disease through vaccination. The crossword solution for this term is 'IMMUNE', which means to be protected from a particular disease or infection due to the body's production of antibodies. Vaccination is a process in which a weakened or killed form of a virus or bacteria is introduced into the body, stimulating the IMMUNE system to produce antibodies that protect against future infection. Vaccines are an important part of public health, helping to prevent the spread of infectious diseases and protecting individuals from serious illnesses.