California is in the midst of a pertussis epidemic. Commonly called whooping cough, the illness has reached levels in the state that have not been seen in fifty years. As of the October 19, 2010 report, 6,257 cases of whooping cough have been reported to the state. Ten infants have died.
The California Department of Public Health (CDPH) is issuing weekly updates at its website about the pertussis epidemic. Many mass media outlets are pointing to Latinos / Hispanics as both the hardest hit by the epidemic and even as the possible source of the epidemic. The data seems to suggest the opposite.
Based upon census estimates from the United States Bureau of the Census, in 2009 California was 37% Hispanic, 13.7 million people out of a state total of 37 million.
Three California counties, San Bernardino, Los Angeles and Riverside, have 38% of the state’s total population. They each have over 44% of their population listed as Hispanic. Yet, they account for only 20% of the whooping cough cases in California.
When the data from the CDPH is examined county by county, the most heavily populated nine counties show some surprising data. The top nine California counties by population account for 70% of the state’s population and 73% of the state’s Hispanic population. In contrast, they account for 48.6% of the state’s reported pertussis cases. Only Alemeda and San Diego counties exceed the state infection rate of 16 per 100,000 population. San Bernardino county, where Hispanics make up 48% of the population, has a pertussis infection rate of only 4.26 cases per 100,000 population.
The California counties with the highest rates of pertussis infection are San Luis Obispo, Marin and Fresno. All three counties have Hispanic population numbers far below the state average, with San Luis Obispo at 9% but holding the highest infection rate of 137.71 cases of pertussis per 100,000 population. Marin comes in at 14.66% and 126.62 / 100,000. Fresno has 25.63% Hispanic population and an infection rate of 53.38 / 100,000.
Time Magazine has an article titled California’s Whooping Cough Epidemic Hits Latino Babies Hardest. In it, anonymous health officials are quoted as blaming the number of cases in the Hispanic community on overcrowding. Fox News quotes a spokesman from the Centers for Disease Control (CDC) as making a similar claim.
Were those claims true, whooping cough infection rates would be highest in those California counties with large Hispanic populations. The opposite appears to be the case from the data.
Dean A. Blumberg, M.D., is quoted in the Fox piece. He has seen outbreaks of whooping cough in areas where parents are electing not to immunize their children. His quote:
“It’s not that they can’t afford it or don’t have access to vaccinations,” said Blumberg, an associate professor of pediatrics at University of California, Davis. “We are seeing geographic clustering in areas with lower immunization rates, where parents choose to opt out because they are reading stuff on the Internet.”
The CDPH itself suggests that African American children are at greatest risk due to having the lowest immunization rates. The data and graphs in the October 19 CDPH report clearly show that whites have the highest infection rates over age 7, and the infection rate for children between ages 6 months and 6 years is virtually identical for white and Hispanic children.
California is one of twenty states that allow parents to refuse to immunize their children based on a personal belief or philosophical exemption. The California Immunization Handbook for Schools has this to say about the exemption:
“California is one of a number of states that allows a personal beliefs, or philosophical, exemption to school/ child care immunization requirements. California law states that “Immunization of a person shall not be required for admission…if the parent or guardian…files…a letter or affidavit stating that the immunization is contrary to his or her beliefs.” Any parent has the option to take the personal beliefs exemption at any time.”
A San Diego State University organization called the Watchdog Institute has done some research on the use of the personal belief exemption in California. Statewide, 2.03% of children entering kindergarten had such exemptions, and 2.63% in San Diego. However, the researchers found that some schools had even higher rates. A private school, the Waldorf School in San Diego, had a rate of 51.2% exempt in those children who began school in the Fall of 2009. Most of the public schools on their list had rates of 5-8%.
Four of the top five states with high case counts allow this exemption. 74% of the total whooping cough cases reported in 2010 are from the 20 states allowing the exemption. States such as Michigan and Ohio have small Latino communities but both are reporting over 1,000 cases of whooping cough for 2010 and both allow the personal belief exemption.
The pertussis epidemic in California is affecting all ages and ethnic backgrounds. The data does not support placing the blame for the epidemic on the Hispanic community. Data, however, does suggest that parents who have exempted their children from necessary immunizations may have strongly contributed to the spread of the disease. Public health professionals will be studying the 2010 origins and spread of whooping cough in California and in the United States for some time to derive lessons learned and preventative strategies for the future.