William Schaffner, MD, is professor of preventive medicine and medicine (infectious diseases) at Vanderbilt University School of Medicine in Nashville, Tenn. Additionally, he serves as a hospital epidemiologist at Vanderbilt University Hospital and is immediate past-president of the National Foundation for Infectious Diseases.

When is a disparity not a disparity?

As I was writing my last blog about the ongoing pertussis outbreak in California, I couldn’t help wondering why the Hispanic community is being so hard hit there. The peak incidence is 547/100,000 among Hispanic infants younger than 6 months; nine of the 10 infants who died from pertussis in California last year were Hispanic; and 80% of hospitalized infants were Hispanic.

It’s tempting to assume that Hispanic infants aren’t getting the recommended pertussis vaccine. But think about it. The peak incidence is among those who haven’t had time to complete the primary vaccine series, so it’s not their own immunization status that’s at issue.

We also know that Mexicans, the primary Hispanic group in California, are generally very positive about vaccines and are vaccine compliant. In fact, Mexico does a great job of vaccinating for pertussis.

One hypothesis for the increased risk among Hispanic infants is that they tend to live in large households, and the disease is highly contagious among the unimmunized. This is a good hypothesis, but we need to be careful of the conclusions we draw from it. Many of those who are unimmunized fall into that category because they are too young (infants) or because their immunity has waned (adolescents and adults).

And the real issue is that all adults, regardless of ethnicity, lose their immunity over time and can spread the disease. The hard hit Hispanic community might actually be a harbinger of even worse outbreaks to come if we don’t face down the issue of waning immunity in all adults.

Make no mistake; health care disparities continue and are a real problem. But in this case, we need to look beyond the difference in ethnicity-related outcomes and focus on the bigger need — making sure that every child and every adult receives recommended vaccines.