A couple of recent cases of pertussis, or whooping cough, at Isle of Wight Academy illustrate the importance of vaccinations, even for adults.

Pertussis is one of three diseases protected against by the Tdap vaccine. It is especially dangerous to young children and infants. That’s why the commonwealth of Virginia requires that children receive the vaccination and booster shots several times before a child enters school.

For years, those shots were thought to be sufficient to protect the population from a dangerous outbreak of whooping cough. Recent isolated outbreaks, however, have called into question the prevailing wisdom, causing health officials to conclude that the immunity granted by the vaccines wears off over time, and vaccinated individuals can still contract the disease as teenagers or adults.

In fact, the Virginia Department of Health now believes that for every adult with symptoms of pertussis, there are five adults who carry the disease but show no symptoms. This is an especially dangerous situation for adults and older children who come into contact with infants. Most infants younger than a year old contract the bacterial infection from an adult.

The disease is highly contagious and causes violent coughing that can cause a litany of complications. According to the Centers for Disease Control, more than half of infants younger than 1 who get the disease must be hospitalized. About one in five infants with pertussis gets pneumonia, and about one in 100 will have convulsions. About 1 percent of cases are fatal, especially in infants.

Health officials now recommend an extra booster shot at age 11 or 12 and for adults who are around children. To that end, the Isle of Wight Health Department held a free vaccination clinic for 47 staff members at Isle of Wight Academy on Friday.

Local health departments offer the Tdap booster in their offices. For more information, call 514-4700 for the Suffolk health department or 357-4177 for the Isle of Wight County health department.