A post on the History of Vaccines blog earlier this month mentioned an outbreak of whooping cough in California, noting that at the time, four infants had already died from the disease. The death count has now reached five, all children less than three months of age, and the total number of confirmed cases reached 910 as of June 15th. The director of the California Department of Public Health declared in a statement that the outbreak is now an epidemic.
The most recent major outbreak of whooping cough was in 2005, when 3,182 cases were recorded in California. This year’s epidemic is on pace to surpass the number of cases from 2005. An outbreak has also been reported in Ohio, and Oregon public health officials have reportedly noted an unusually high number of cases there as well.
Whooping cough can be prevented by vaccination, but the first dose of the vaccine is not given until two months of age. Prior to that infants are highly susceptible to the disease, which is often spread by adults. A booster vaccine against whooping cough is available for adults as part of the Tdap (tetanus, diphtheria, pertussis) immunization, which can be substituted for one tetanus or Td vaccination between the ages of 19 and 64. The Advisory Committee on Immunization Practices (ACIP) recommends Tdap vaccination for adults who have contact with infants younger than 12 years of age.
The threshold of herd immunity for whooping cough has been placed at approximately 93%. Public health officials are concerned that the disease’s spread may grow in California–a state with one of the highest levels of vaccine refusal–and throughout the country.