INDIANAPOLIS -- Four additional cases of whooping cough were reported this week in central Indiana schools, heightening the concern of parents.

Cases of pertussis, the medical name for whooping cough, are on the rise across the country. Locally, Geist Elementary School reported a case last week, and Lawrence Township has confirmed four cases at three schools -- Forest Glen, Amy Beverland and Mary Castle, 6News' Ericka Flye reported.

An informational letter was sent home to parents Wednesday, recommending that children be up to date on their vaccinations and see a doctor if they've been in contact with anyone who has pertussis.

The Indiana State Department of Health said that while the illness is more common in children, adults can also contract mild to severe whooping cough and everyone should be vaccinated.

"The more people who get vaccinated, it provides protection for children and the elderly and those who can't get vaccinated," said Angie Cierzniewski, of the Health Department.

Health experts said immunity from the vaccine wanes over time, so it's important to stay up to date. For infants especially, contracting whooping cough can be fatal.

Craig and Katie Van Tourhout, of South Bend, lost their newborn baby, Callie, to the disease.

"She was a healthy baby. She just got a little cough. Things went downhill," Craig Van Tourhout said.

Callie's cough became more persistent. She died at 38 days old.

The Van Tourhouts warn everyone to get vaccinated, a message a now grieving mother said she never got.

"We had no idea whooping cough vaccination was something they wanted mothers to have. No one mentioned it to us. Nobody brought it up to us. Nobody talked about it. We honestly had no clue," Katie Van Tourhout said. "We're speaking out because we want to help somebody else's baby who goes through this."

In Indiana, children must be vaccinated for whooping cough at 2, 4, 6 and 15 months. They should then get a booster shot before kindergarten.

Children in grades six through 12 are required to have the immunization for school.

There were 400 reported cases of whooping cough in Indiana in 2009.