Have you ever seen a case of pertussis, otherwise known as 'whooping cough?' Chances are good that if you never have you may soon, since 2012 had the dubious distinction of being the year with the most cases of pertussis occurring nationally, that's about 38,000, since 1959. As Rick and I discuss on PodMed this week, pertussis is just one of a number of reportable, vaccine-preventable diseases chronicled in a retrospective analysis in NEJM entitled, "Contagious Diseases in the United States From 1888 to the Present," and many of which are increasing in incidence, mostly for indefensible reasons.
First of all, we'd both like to laud the authors of this paper for the massive investigation and data crunching represented herein. Investigators digitized all weekly surveillance reports of nationally notifiable diseases between 1888 and 2011. This represented almost 90 million individual cases, further characterized by both date and geographic location in the United States. Eight vaccine-preventable contagious diseases were selected from the dataset for further analysis: polio, measles, rubella, mumps, hepatitis A, diphtheria, pertussis and polio. For seven of these eight diseases the authors estimated the number of cases that have been prevented since the introduction of a vaccine for the disease, using the year of the specific vaccine introduction as the cutoff date. Smallpox was eliminated from this analysis since the vaccine was introduced in 1800 and no estimate of preventive capability was therefore possible. Interestingly, not one of the 56 notifiable diseases reported since 1888 was continuously reported during this period, which the authors attribute to "shifting public health priorities and challenges."
So what did this analysis find? Not surprisingly, most infectious diseases prior to the development and release of vaccines had more or less predictable patterns of outbreaks and epidemics, often seasonal, followed by a period of reduced transmission. Once an effective vaccine was introduced and used widely, that pattern was eliminated and the number of cases of each disease declined rapidly. The authors calculate that 103.1 million cases of these infectious diseases were prevented because of the employment of effective vaccines, assuming that all of the decline in incidence before and after vaccine introduction was due to the vaccine. As I comment to Rick in the podcast, this seems to be an unrealistically low estimate to me, and the investigators concur, citing under-reporting as one factor that likely lowered cases of reportable diseases as well as the probability that under-reporting occurred more often in the pre- rather than post-vaccine introduction period. In any case, the analysis clearly establishes vaccines as a success story and should enable clinicians to stress their virtues to the distressingly large number of parents who seem reluctant to have their children vaccinated.
Rick and I agree with the authors that persistent urban myths related to vaccination dangers to offspring must be dispelled repeatedly and public health measures supported to ensure proper vaccination, including enforcement of school attendance policies. As a primary conduit of infection, children must be vaccinated to safeguard the health of all, especially very young infants and older folks whose immune response has declined. Perhaps primary care physicians could employ video of a child with whooping cough to bring home the point that worldwide, almost 300,000 deaths still occur from this disease.
Other topics this week include a disappointing response to the latest HIV vaccine candidate, also in NEJM, micronutrients in early HIV infection and thalidomide for kids with refractory Crohn's disease in JAMA. Until next week, y'all live well.