REDDING, Calif. -

Shasta County health officials say it’s not a matter of if, but when there’s an outbreak of preventable contagious disease, unless more children are immunized.

Health Officer Andrew Deckert briefed the Public Health Advisory Board about how the percentage of children being immunized has dropped below safe levels.

“If you look at all the kids entering kindergarten [with] all their immunizations up to date under the standard child immunizations,” Deckert said, “It used to be 90 percent, 97, 98 percent not that long ago ... and now, last year it was about 77 percent.”

The Public Health Advisory Board calculates the safe percentage of immunized children by what is called the herd immunity threshold, which is the percentage of children vaccinated, that protects not only them, but the children who haven’t been vaccinated from preventable diseases.

The standard is 94 percent. California dips just below that level with a little more than 93 percent of children vaccinated.

Shasta County’s numbers were even worse, standing at 83 percent, 10 percent lower than the herd immunity threshold.

Preventable diseases include the measles, mumps and rubella.

Dr. Deckert said we’ve already seen our first outbreak, a bout of whooping cough that spread among children in 2010.

Deckert said getting your loved ones immunized is crucial.

“It’s not too late,” Deckert said, “It’s never too late to make a difference.”