California had the highest number of cases of whooping cough (pertussis) in 60 years, despite the fact that it has a readily available vaccine. A new study in The Journal of Pediatrics describes that 2010 whooping cough epidemic and details strategies to decrease the incidence of this infection.

Some science education would be a good place to start. California has a strong anti-vaccine mentality, especially in coastal regions, and results showed much higher incidents of Whooping Cough in those areas, despite those being high income, well-educated communities.

Whooping cough is almost as contagious as measles, affecting ~12-17 individuals with each case, so clinicians are required to report cases of this bacterial respiratory tract infection to the state's department of public health.  This gave Kathleen Winter, MPH, and colleagues from the California Department of Public Health (CDPH) data on 9,154 cases of whooping cough with onset between January 1 and December 31, 2010; 809 cases were hospitalized and 10 resulted in death. All deaths and most of the hospitalized cases (62%) were in infants less than 3 months of age, and infants less than 6 months of age had the highest disease rates. In children and adolescents ages 1-18 years, Whites had the highest incidence. 

Why the sudden resurgence? Infants receive 4 doses of DTaP (diphtheria, tetanus, and pertussis) vaccine by 18 months of age, and children should receive whooping cough "booster" doses at 4-6 years of age (DTaP) and 11-18 years of age (Tdap). 

In response to the sharp increase of cases in 2010, CDPH implemented a public health campaign to distribute educational materials to health care providers and the public to stress the importance of rapid diagnosis and treatment, especially in young infants, under-immunized children 7-9 years old, and pregnant women, and provide free Tdap booster vaccines.

To decrease the occurrence of whooping cough in infants who are too young to be vaccinated, it is important to immunize household and family members who will be in close contact with the baby (a strategy known as "cocooning") and increase the immunity of the population as a whole to decrease infants' exposure to pertussis. 

In 2011, the Centers for Disease Control and Prevention recognized the extreme vulnerability of young infants and recommended universal Tdap immunization for pregnant women (after the 20th week of gestation) who previously had not received Tdap. According to Winter, "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. In addition, it is critical that providers continue to be vigilant and promptly diagnose and treat young infants with whooping cough."

The number of cases of whooping cough was elevated in pre-adolescents, even when they are fully vaccinated, indicating that protection from the 5-dose DTaP series may wane before the Tdap booster is given, though the decrease in cases of 11-14 year olds suggests that Tdap is effective for adolescents.