The state of Washington has approved the use of the DTaP vaccine for school-aged children and their families.
The state of California and 15 other states approved the vaccine on Monday.
The first doses are expected to be administered on Tuesday.
The first DTaPs vaccines have been administered in the United States since the first vaccine was introduced in 1993.
More:The United States and the United Kingdom both approved the first DTap vaccines in 2015.
In 2017, the U.S. approved a second vaccine.
And in 2016, the World Health Organization approved the fourth vaccine.