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Descriptive Epidemiology Data Prove Extremely Valuable In Setting
Vaccine Policy And |
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Author: Roger Bernier MPH, PhD “A simple yet novel idea”. That’s how Matthew Moore and Cynthia Whitney, epidemiologists at the Centers for Disease Control and Prevention in Atlanta, describe an active surveillance program that was population- and laboratory-based for invasive bacterial infections, including those caused by Streptococcus pneumonia. The modest goal of the program was to identify and characterize these infections, however, the descriptive surveillance data have contributed in substantive ways “to every pneumococcal vaccine policy decision in the past 20 years,” according to Moore and Whitney writing in the journal Emerging Infectious Disease published ahead of print (see below). Scope of Surveillance The program begun two decades ago initially tracked invasive pneumococcal disease in 7 states with a population greater than 19 million and grew to include other sites covering 31 million persons by 2014. The methods used to count cases were audits of clinical laboratories where specimens were tested coupled with reviews of medical records in each site to ascertain underlying conditions and discharge status. Estimates of disease burden in this population have been provided annually since 1998. Risk Assessments Moore and Whitney provide multiple examples in their article of how descriptive data proved useful for vaccine policy. Data showing an increased risk in infants not eligible at the time for vaccination and in older persons who were eligible but not vaccinated influenced vaccine advisory bodies to recommend pneumococcal vaccine for children and to intensify efforts to raise coverage for adults over 65. Descriptive data on cases and antimicrobial resistance was used to shape treatment policy for pneumonia and meningitis. Sometimes data from special studies were used--- not to recommend more vaccination but to recommend limiting the age at which adults should be targeted for vaccination. This was shown to be desirable because the existing target age recommendation already included most of the high risk persons. This fact was not known when the question about broadening the target age for vaccination first arose. Natural Experiments The existence of the ongoing surveillance program allowed investigators to take advantage of “natural experiments” when vaccine shortages occurred to evaluate different vaccine dose schedules. This work produced evidence that using three instead of four doses of vaccine for children could produce very high efficacy. Modes of Transmission An interesting payoff of the surveillance data on asymptomatic infections was to elucidate the dynamics of pneumococcal transmission. While the primary driver for immunizing children was initially the prevention of otitis media, subsequent surveillance data showed that because vaccinated children were not being colonized with pneumococci to the same extent, population-based surveillance data showed that disease in adults decreased as well. According to the authors, “… a key driver after [vaccine] introduction was the reduction in adult disease…The cost per IPD (invasive pneumococcal disease) episode averted without consideration of herd protection was $33,000, and the cost per episode averted with herd protection decreased to $5,500. This observation fundamentally changed the method for cost-effectiveness analyses of pneumococcal conjugate vaccines, not only in the United States but also in other countries.” Broadening the Recommendation Despite the success of pneumococcal vaccines in reducing disease in children and adults, surveillance data showed that the remaining disease burden in adults was sufficiently high for CDC’s vaccine advisory group to recommend pneumococcal vaccine in 2014 not only for high risk persons but for all adults 65 years or older. According to the authors, this was perhaps “the widest-ranging” change in vaccine policy made possible by the descriptive surveillance data. In concluding their review, the authors re-emphasize that the surveillance programs “have contributed in fundamental ways to every pneumococcal vaccine recommendation in the United States since 2000.” To read the article, visit: https://tinyurl.com/osf2p5e ■
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