Health World — 22 July 2012

The number of whooping cough cases in the United States may reach a record high in 2012, a spike most likely caused by the waning effectiveness of the pertussis vaccine, according to the U.S. Centers for Disease Control and Prevention (CDC).

Whooping cough, also known as pertussis, is a highly contagious bacterial infection of the respiratory tract. Nearly 18,000 cases have been reported this year, causing the deaths of nine infants.

“That’s more than twice as many as we saw last year at this time,” said Dr. Anne Schuchat, director of the CDC’s National Center for Immunizations and Respiratory Diseases. “In fact, that’s more than we’ve seen in the past five years.  We may be on track for a record-high pertussis rate this year.”

Vaccines which provide immunity against pertussis include DTap, which is administered to children younger than seven, and Tdap, a booster immunization typically given at age 11 and older. Without the booster shot, doctors say the original vaccine can lose its effectiveness, which may be why cases are spiking now.

According to the CDC, pertussis outbreaks come in waves every three to five years. During the first half of 2012, 37 states reported pertussis increases.

Washington State is particularly hard hit, with 2,500 cases of whooping cough in the first half of the year, a 1,300 percent increase from 2011. Most were teenagers who were vaccinated as young children, according to the CDC.

“What is happening in Washington State is a reflection of the larger national picture of this very difficult-to-control disease,” said Schuchat, who recommends booster shots for teens, as well as vaccinations for all pregnant women and people who will have contact with infants.

A new study of California’s 2010 whooping cough epidemic, published in the Journal of Pediatrics also addressed the need for booster shots and the vulnerability of infants to pertussis.

The California Department of Public Health (CDPH) evaluated 9,154 whooping cough cases, including 10 deaths, all infants less than three months of age. Latinos less than 6 months old had the highest incidence of whopping cough. Whites had the highest incidence between 1 and 18 years of age.

The Department recommends that infants receive four doses of DTap vaccine by 18 months of age. DTap booster shots are recommended at 4 to 6 years of age and Tdap boosters at 11 to 18 years of age. Adults are also encouraged to receive Tdap boosters because the vaccine’s waning effectiveness over time.

In response to the state’s epidemic, the CDPH also implemented a public health campaign, recommending vaccinations for pregnant women, adults over 64 years of age, under-immunized children between seven and nine years of age, and for family and household members of infants too young to be vaccinated.

“In the absence of better vaccines, it is imperative that strategies to protect young infants directly, such as maternal vaccination during pregnancy, be evaluated for effectiveness,” said lead researcher Kathleen Winter. “In addition, it is critical that providers continue to be vigilant and promptly diagnose and treat young infants with the whooping cough.”

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Mary Krasn

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