Do I need to worry about my older kids getting pertussis if they were vaccinated as babies?

Almost all adults are susceptible to pertussis, or whooping cough. Between 60 and 80 percent of infants are protected after the first 3 doses of vaccine, but this protection begins to disappear when they are toddlers. After the 4th immunization at 18 months old, 80 percent are protected for the next 3 to 4 years. The 5th dose, at kindergarten entry, protects them for another few years. A booster vaccine is given to adolescents at 11 years of age or above.

People who have been exposed to probable or confirmed pertussis should either receive a course of preventative antibiotics (and I say this as someone strongly opposed to the overuse of antibiotics), or be kept home from daycare, school, or work for at least 2 to 3 weeks.

Children under age 7 who have been exposed should receive a pertussis vaccine, unless they have already had 4 doses of pertussis vaccine (and the last dose within 3 years), or unless there is a compelling reason not to immunize them.