Researchers say an increase in whooping cough cases in Minnesota elementary school students is further evidence that the pertussis vaccine loses its potency before children receive a booster shot at age 11 or 12, the Star Tribune reports.
The Centers for Disease Control and Prevention recommends a booster at age 11 or 12. But the CDC studied whooping cough infection data for Minnesota and Oregon children and found a spike among vaccinated kids ages 7 to 10, starting in 2006.
There was no comparable increase in cases among other age groups, according to a report published Monday in the journal Pediatrics.
The researchers examined data for more than 400,000 Minnesota and Oregon children, Reuters reported.
The children, born between 1998 and 2003, received the recommended series of five DTaP shots, the last of which is given at ages 4 to 6, Reuters reported.
The researchers then looked at the following six years and found 458 kids from Minnesota contracted whooping cough, Reuters reported. The rate of new cases increased from 16 per 100,000 children in the first year after their most recent DTaP shot to 138 per 100,000 in year six, Reuters reported.
Among the CDC's fast facts on pertussis:
In 2010, 27,550 cases were reported in the U.S., but many more go undiagnosed and unreported. This is the most number of cases reported in the U.S. since 1959 when 40,000 cases were reported. In 2011, 18,719 cases were reported.
Coughing fits due to pertussis infection can last for up to 10 weeks or more; sometimes known as the "100 day cough."
Pertussis can cause serious illness in infants, children and adults and can even be life-threatening, especially in infants.