9 Dead From Whooping Cough

California's whooping cough epidemic is on track to break a 55-year record, with 4,017 infections and nine deaths statewide this year, according to state health officials.

Whooping cough is a highly contagious, cyclical illness that peaks in number of infections every five years. This is a peak year, and is on track to exceed the record 4,949 cases reported in 1955.

Symptoms might appear similar to the common cold, but a persistent cough that lasts weeks may indicate the illness, which is also known as pertussis.

All of the deaths occurred in babies too young to be fully immunized against the illness.

State health officials are urging parents and caregivers to get booster shots to create a cocoon of immunity around vulnerable children.

More and more parents are choosing not to vaccinate their children. In fact, the number of parents opting out has nearly quadrupled in the last 20 years.

A report by the San Diego Watchdog Institute found parents are mainly choosing not to immunize their kids against the measles, mumps, and whooping cough. 

State department of public health spokesman Ken August says children who aren't vaccinated may be required to stay home under the authority of county health departments, in the event of an outbreak.