At a Los Angeles media briefing in 2010, Mariah Bianchi describes how her own case of whooping cough caused the death of her newborn son. Reed Saxon/AP hide caption

itoggle caption Reed Saxon/AP

Nurse Fatima Guillen (left) gives 4-year-old Kimberly Magdeleno a whooping cough booster shot at a health clinic in Tacoma, Wash., in May. Ted S. Warren/AP hide caption

itoggle caption Ted S. Warren/AP

Pharmacist Kristy Hennessee administers a vaccination against whooping cough in Pasadena, Calif., in 2010. Vaccinations are the most powerful weapon for slowing the epidemic, but there are growing concerns that the current vaccine doesn't last as long as expected. Robyn Beck/AFP/Getty Images hide caption

itoggle caption Robyn Beck/AFP/Getty Images

A nurse in Washington administers the whooping cough vaccine to a child in May. In response to the epidemic, more than 82,000 adults have also received the vaccine this year. Ted S. Warren/AP hide caption

itoggle caption Ted S. Warren/AP

Nurse Susan Peel gives a whooping cough vaccination to a high school student in Sacramento, Calif. The whooping cough vaccine given to babies and toddlers loses much of its effectiveness by the time people reach their teens and early adulthood. Rich Pedroncelli/AP hide caption

itoggle caption Rich Pedroncelli/AP

Nurse Susan Peel gives a whooping cough vaccination to a student at Inderkum High School in Sacramento, Calif., in 2011. Now it seems likely such shots will become routine for senior citizens, too. Rich Pedroncelli/AP hide caption

itoggle caption Rich Pedroncelli/AP