Five candidates are writing their national secondary school tests at Vihiga County Referral Hospital in Mbale.
The boy and four girls were admitted with different illnesses on Tuesday, the seventh day of the Kenya Certificate of Secondary School Education (KCSE) examinations.
County Director of Education Mr Thaddeus Awuor said the boy, from Chavogere Secondary School in Sabatia, was diagnosed with malaria.
A candidate at Iginga Girls' in Sabatia is epileptic while one at Gilwazi Mixed Secondary broke her leg on Monday evening.
Two other girls from Kapchemgun Mixed in Hamisi and Ideleri were also found to have malaria.
Mr Awuor said education officials will ensure the candidates are comfortable.
"They will be taken back to their examination centres once they recover. We pray that they recover quickly," said Mr Awuor.
Regarding the integrity of the exams, Mr Awuor said officials from the Education and Interior ministries were ensuring strict supervision.
He noted that no cases of cheating have been reported so far.
Some 14,485 candidates are taking the tests in 162 centres in the rural county.