Most kids enter elementary school with the shots they need to protect them from childhood disease. But two reports issued in August show why public health officials worry that school systems may be allowing too many exceptions to vaccine requirements.
And those exemptions -- for medical, religious or philosophical reasons -- may put some kids' collective immunity at risk.
Roughly 5 percent of U.S. students entering kindergarten were exempt from at least one required vaccine last year, but individual states excused up to 7 percent of the youngsters from shots, the federal Centers for Disease Control and Prevention reported last month.
All states allow exemptions for medical reasons such as allergies or immune system problems. All but two -- Mississippi and West Virginia -- allow them on religious or philosophical grounds, such as refusing intrusive medical care.
There have been some efforts to tighten exemption requirements. Washington state last year imposed a new rule that parents have to meet with a health-care provider before being granted a philosophical exemption. The proportion of kindergarteners with exemptions dropped from 6 percent to 4.5 percent from the year before
A similar change has been proposed in California in a bill introduced by an assemblyman who is a pediatrician.
According to the CDC report, nine states had exemption rates of 4 percent or higher, led by Alaska at 7 percent, while 10 states had exemption rates of under 1 percent, led by Mississippi at 0.01 percent.
But nationwide, the CDC says, about 95 percent of kids starting elementary school last year had received at least a couple of doses of vaccines against most childhood diseases like measles, mumps, diphtheria and pertussis.
Of more than 4.1 million incoming kindergartners nationwide, more than 89,000 were exempted from vaccinations. Relatively few exemptions -- 11,000 to 13,000 a year -- were for medical concerns. CDC officials note that exemptions tend to cluster in certain communities, leaving those children more vulnerable to outbreaks.
A new, separate analysis of medical exemptions -- done by scientists at Emory University in Atlanta and published online Aug. 30 by The Journal of Infectious Diseases -- also shows major differences in standards for excusing kindergarteners from state to state. The analysis covers seven years, from 2004 through 2011.
States that had the easiest standards for granting medical exemptions approved nearly half-again as many exemptions as states with the toughest requirements.
Researchers rated the exemptions based on six administrative requirements: a written doctor's statement of need; a separate medical exemption form; approval from the health department; certification that the exempting physician can practice in the state; annual approval and notarization of exemption forms.
Each requirement was given a one-point score, and states that had zero or one of the requirements were ranked "easy" -- 30 fit that category. Seventeen states were rated 2, or "medium." Three states were rated 3 or above, and categorized as "difficult."
Medical exemptions were granted permanently -- throughout the child's school years -- in seven states and temporarily only in five, with the rest allowing some combination. Experts say medical exemptions should be periodically revisited because children and vaccines change over time.
Saad Omer, senior author of the Emory study, said it appears that some parents and physicians are more likely to seek medical exemption from vaccines in jurisdictions where they are easy to obtain, even though almost all states also allow parents to seek philosophical or religious exemptions, too.