Is your child at risk for whooping cough?

State and county health officials are pushing parents to make sure their middle- or high-school students' shot for whooping cough is up to date, ahead of a new state law requiring such booster immunizations.

Beginning July 1, any student attending seventh through 12th grade in California must have proof of a Tdap booster shot for the cough, also known as pertussis.

A spokesman for the state Department of Public Health said through the first four months of 2011, documented cases of pertussis are up from the same period last year, when the number rose to what he called epidemic levels.

"It was the worst the state has seen in 60 years," said Ralph Montano of early 2010, when the state had 749 cases, and by the end of the year, 10 fatalities.

This year, 1,189 cases have been documented through the end of April, though so far no one's died, which Montano said is an encouraging sign. The higher number of cases may be because doctors are diagnosing it more often, he said.

Infants are immunized against pertussis, and along with immunizations for other shots, proof of a pertussis shot is required before a child enters kindergarten.

Because the immunizations lose effectiveness over time, children and teens need the booster shot to keep pertussis, a bacteria, from infecting school populations.

Lou Anne Cummings, Sutter County's chief health officer, said the county's had two documented cases so far this year.

"We know it's out there," she said. "And the normal se son for whooping cough is in summer and fall, so we could see more."

Parents should contact their family pediatrician or health care provider to get the shot if they haven't done so already, Cummings said.

A booster shot requires just one prick, and supplies are plentiful, Montano said.

The disease tends to be most deadly to infants and those with compromised immune systems, according to Cummings.

"We've really had a lot of freedom from killing diseases like this for decades," she said. "The thing about whooping cough, it's the infants that die."