SAN DIEGO - Time is running out for students in San Diego County to get their Tdap booster shots, school officials said Tuesday.

Due to the passage of Assembly Bill 354 -- California students 7th through 12th grades must have a tetanus, diphtheria and pertussis booster shot.

According to the San Diego County Office of Education, 90 percent of the county's students have the required combined tetanus, diphtheria and pertussis vaccine.

“The Tdap vaccination is in response to the threat of a whooping cough epidemic, if you will, in our state,” said Grossmont Union High School District Superintendent Ralf Swenson.  “It’s a very serious disease and unfortunately the vaccination that our students had when they’re younger don’t last through their high school careers.”

In the Grossmont district, about 1,000 students need to prove they’ve had the vaccination by Friday or they’ll have to stay home. Swenson said this is a major problem.

“It’s hard to teach an empty chair,” said Swenson.  “It’s important to be in class, it’s important to be in school and to miss several days for something like this would have a negative impact on the students educational experience and we just don’t want to see that happen to them.”

Swenson said not only will students miss out on classes, if they’re involved in extracurricular activities - they’ll be banned from doing that, too.

A spokesperson with San Diego Unified School District, said there are less than 5,000 students who need to be immunized.

The California Immunization School Law as complete information about the Assembly Bill 354 and exemptions online.