It is not clear that the latest National Immunization Survey results in New Jersey accurately reflect actual vaccination rates. The survey, conducted from July 2007 through June 2008, found that 70.5 percent of children in New Jersey had received the standard series of vaccines - down from 80.5 percent during the January-to-December 2007 period. The state's rank plummeted.
Twelve-month results from the rolling survey are reported every six months, and they include a six-month overlap.
Although the decline in New Jersey was steep, small sample sizes in each period for each state produce large margins of error, said Jim Singleton, chief of the U.S. Centers for Disease Control and Prevention's assessment branch, which conducts the survey.
In this case, the margin of error for New Jersey was plus or minus about 7 percentage points in each period - enough to produce an overlap that potentially wipes out the decline.
"What we try to tell the states is that you've got to look at the long-term trend year by year," Singleton said. Over the years, New Jersey's vaccination rates have roughly matched the national average - just over 77 percent.
Pennsylvania's rate in the latest survey rose slightly, to 79.9 percent from 78.8 percent.
The New Jersey Department of Health and Senior Services, which sets policy, but does not administer vaccines, has not yet analyzed the most recent data in detail.
"We're certainly concerned about any decline and are looking into it to better understand the reasons," the department said in an e-mail statement Friday evening.
"One key factor may have been the shortage of pneumococcal vaccine in 2007 and 2008, which affected different states at different times," the statement said, adding that "health-care providers have been working hard since the shortage ended last spring to bring children back in and get them caught up."
