HealthDay News — In the 2010 California pertussis epidemic, all deaths and most hospitalizations occurred in infants younger than 3 months of age, according to research published online July 19 in the Journal of Pediatrics.

Kathleen Winter, MPH, from the California Department of Public Health in Richmond, and colleagues evaluated clinical and demographic information for all pertussis cases reported to the department from Jan. 1 through Dec. 31, 2010.

Hispanic infants aged younger than 6 months had the highest disease rates, the researchers found. Most hospitalizations and all deaths (62%) occurred in infants younger than 3 months. Among cases that occurred in those aged 6 months to 18 years, 9% were completely unvaccinated against pertussis. Most pediatric cases occurred in children that  were vaccinated according to national recommendations, the researchers noted.

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Fully-vaccinated preadolescents, particularly 10-year-olds, experienced elevated disease rates, suggesting that protection from the five-dose diphtheria, tetanus, and pertussis (DTaP) vaccine series may wane before the tetanus, diphtheria and acellular pertussis (Tdap) vaccine booster is given.

Based on these findings, Winter and colleagues made several suggestions to mitigate future outbreaks, including:

  • Administering Tdap vaccine to adults older than 64 years of age, under-immunized children aged 7 to 9 years old and pregnant women (after the 20th week of gestation)
  • Immunizing household and family members who will be in close contact with infants
  • Distributing free Tdap booster vaccines to hospitals, community health centers and Native American health centers for pregnant and postpartum women and other infant contacts
  • Providing better clinical guidance on the diagnosis and treatment of pertussis in young infants 
  • Increasing education efforts about the risk for disease among the public and health-care providers

“In the absence of better vaccines, it is imperative that strategies to protect young infants directly, such as maternal vaccination, be evaluated for effectiveness,” the researchers wrote. “In addition, it is critical that providers continue to be vigilant and promptly diagnose and treat young infants with pertussis.”

Current pertussis vaccine guidelines state that infants should receive four doses DTaP vaccine by 18 months of age, and children should receive DTaP whooping cough “booster” doses at 4 to 6 years of age, and Tdap at 11 to 18 years of age.

Adults are also encouraged to receive the Tdap booster because immunity from both the disease and the vaccine wanes over time, the researches wrote.

Winter K et al. J Peds. 2012; doi: 10.1016/j.jpeds.2012.05.041.