There has been 113 reported cases in Boulder County as of last week. Statewide cases of the bacterial disease has reached 940 cases. That's more than double all of last year.

9NEWS Health Expert Dr. John says two there are two reasons the number of cases are up: a weaker vaccine and too many kids who weren't vaccinated in the first place.

He says if you have insurance getting the shot now should be free. If you do not have insurance, state health departments offer the vaccine often at reduced prices.

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