SALT LAKE CITY — Parents of students at Skyline High School received recorded phone messages and a letter from the Salt Lake Valley Health Department on Wednesday, reminding them to keep students up to date on pertussis vaccinations.

A waning efficacy of the vaccine means people need booster doses to prevent illness and decrease further dissemination of the disease.

The action was prompted by surveillance of the spreading illness, and the fact that epidemiologists may have identified a point of contact that involved a large number of people, said department spokeswoman Pamela Davenport.

"We'd like to think that kids that age have had the booster vaccine," she said.

Davenport said individuals who were fully vaccinated as children may be vulnerable without the TDaP vaccine, to prevent tetanus, diphtheria and pertussis (whooping cough) in teens and adults. Anyone who is around infants, who aren't fully immunized and are most susceptible to the disease, should get the booster shot, she said.

Pertussis cases are on the rise through much of the country and in Utah. The Utah Department of Health has reported 922 cases through the end of last week. In all of 2011, there were 618 cases statewide, 457 of which had been reported by this time last year, according to health department data.

Officials expect the numbers to continue to climb through the winter season, when people tend to spend much more time indoors, therefore increasing the possibility of spreading the infectious disease.

Skyline is the only school in the valley to receive the notice, but the health department is keeping a close watch on the spread elsewhere, Davenport said. There have been two confirmed cases of pertussis and one suspect case at the high school.

Pertussis, which exhibits symptoms similar to that of a common cold, including runny nose, fever and severe cough, can last several weeks and months.

"It used to be called the 100-day cough," Davenport said. Even though symptoms may diminish over time, she said it can still be contagious. Pertussis can be treated with antibiotics if it is caught early enough.

Anyone with questions, or to make an appointment for the vaccine, is asked to call their primary care provider, or the Salt Lake Valley Health Department at 385-468-7468.

E-mail: [email protected]

Twitter: wendyleonards