South Sudan has not communicated its Yellow Fever vaccination requirements. For your protection, vaccination is recommended for all travellers 9 months of age and older since Yellow Fever is endemic throughout the country.
Countries may change their vaccination requirements without notice and in some instances border agents use their discretion to deny entry despite the officially stated requirements.
If there is risk of Yellow Fever at your destination, whether vaccination is required for entry or not, be prepared to show a certificate of vaccination or a waiver stating the medical reasons for not being vaccinated.
If your medical practitioner has advised you against the Yellow Fever vaccine, take meticulous anti-mosquito bite measures during the daytime in Yellow Fever risk areas. More details on insect bite prevention.