Pertussis Epidemic in California (2010)

Stephen Barrett, M.D.

California has reported that the number of reported deaths and illnesses this year due to whooping cough (pertussis) is the highest in 52 years. Pertussis is a highly contagious disease. Unimmunized or incompletely immunized young infants are particularly vulnerable. Pertussis vaccination is supposed to begin at two months of age, but young infants are not adequately protected until the initial series of three shots is complete at 6 months of age. For this reason, it is important that others who may have contact with infants, including family members, healthcare workers, and childcare workers, should also be vaccinated. As of August 24, 2010, 3,311 confirmed, probable, and suspect cases of pertussis have been reported. This number includes eight deaths and at least 169 hospitalizations.

Most of the children appeared to have acquired the infection from parents or caregivers who didn't know they were infected. Two factors have contributed to the epidemic. One is that many parents who have encountered misleading information are afraid that vaccination is dangerous. The other is that insurance reimbusement rates are so low that some doctors are not encouraging their adult patients to have the recommnended booster shots.

Pertussis is one of the most contagious human diseases, so it is a great risk to those who are unvaccinated. Pertussis will develop in 90% of unvaccinated children living with someone with pertussis, and in 50% to 80% of unvaccinated children who attend school or daycare with someone with pertussis. About 50 out of every 10,000 people who develop pertussis die from the disease.

Before widespread vaccination against pertussis, the disease infected as many as 147,000 people in the U.S. each year between 1940 and 1945 and killed nearly 8,000. By 1976, there were only 1,010 cases of whooping cough in the U.S., the lowest number ever reported. Since then, the incidence of pertussis has been rising, due in part to improved reporting of cases. The chart below depicts how pertusses rates dropped sharply after immunization became available and have risen in recent years.

Number of reported pertussis cases by year of onset -- California 1950-2010*

Additional Information

This article was revised on August 28, 2010.

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