Sheikh `Abdul-Majeed Subh, a prominent Azharite scholar, states: The term “unbelievers”, includes the People of the Book in its general and basic sense. But the Glorious Qur’an gives them some special rulings. When referring to the People of the Book in the following verse, Almighty Allah used the conjunction which signifies that they have special rulings. Almighty Allah says, “Those who disbelieve among the People of the Scripture and the idolaters could not have left off (erring) till the clear proof came unto them.” (Al-Baiyina: 1)”
Given the above, it should be also clear that the term unbelievers include all those who associate others in worship with Allah. May Allah guide you and us all to right path.