Concepts and Methods in Infectious Disease Surveillance

Nkuchia M. M'ikanatha, John Iskander, Nkuchia M. M'ikanatha, John Iskander

• Publisher: Wiley-Blackwell
• Year: 2014
• Print ISBN: 9780470659397
• eBook ISBN: 9781118928639
• Edition: 1
• Topic: Medicine
• Subtopic: Infectious Diseases

Infectious disease surveillance has evolved at an extraordinary pace during the past several decades, and continues to do so. It is increasingly used to inform public health practice in addition to its use as a tool for early detection of epidemics. It is therefore crucial that students of public health and epidemiology have a sound understanding of the concepts and principles that underpin modern surveillance of infectious disease. 

Written by leaders in the field, who have vast hands-on experience in conducting surveillance and teaching applied public health, Concepts and Methods in Infectious Disease Surveillance is comprised of four sections. The first section provides an overview, a description of systems used by public health jurisdictions in the United States and legal considerations for surveillance. The second section presents chapters on major program-area or disease-specific surveillance systems, including those that monitor bacterial infections, foodborne diseases, healthcare-associated infections, and HIV/AIDS. The following section is devoted to methods for conducting surveillance and also approaches for data analysis.  A concluding section summarizes communication of surveillance findings, including the use of traditional and social media, in addition to showcasing lessons learned from the New York City Department of Health's experience in surveillance and epidemiology training.

This comprehensive new book covers major topics at an introductory to intermediate level, and will be an excellent resource for instructors. Suitable for use in graduate level courses in public health, human and veterinary medicine, and in undergraduate programs in public-health-oriented disciplines, Concepts and Methods in Infectious Disease Surveillance is also a useful primer for frontline public health practitioners, hospital epidemiologists, infection control practitioners, laboratorians in public health settings, infectious disease researchers, and medical and public health informaticians interested in a concise overview of infectious disease surveillance.

SECTION II
Specific Surveillance Systems

CHAPTER 5
Surveillance for Vaccine-Preventable Diseases and Immunization

Daniel C. Payne

Centers for Disease Control and Prevention, Atlanta, GA, USA

Introduction

Vaccine-preventable disease (VPD) surveillance is grounded in a firm understanding of the pathogenesis, clinical course, epidemiological risk factors, and molecular characterization of the disease agent targeted for vaccination. Therefore, VPD surveillance begins well before the vaccine is even developed, approved, and widely administered. The clinical, epidemiological, and laboratory characteristics of the disease agent are the foundations for developing valid, scientifically accurate assessments of the VPD in populations during the widespread use of the vaccine.

Critical functions of VPD surveillance activities are those that evaluate vaccine policy, including understanding pathogen epidemiology, vaccine impact, vaccine coverage, safety, and effectiveness. A lab component could monitor for molecular changes, whether influenced by the vaccination program (e.g., when the pathogen genetically adapts to post-vaccine selective pressures) or not (e.g., through antigenic drift). Continued monitoring over time is important and may lead to unexpected findings. Communicating these results through peer-reviewed publications, scientific conferences and symposiums, reports to governmental and industry oversight boards, domestic and international networks, and healthcare providers ensures that the scientific and regulatory communities accumulate a common knowledge of these findings, and can therefore tailor assessments and recommendations appropriately.

In this chapter, we will describe the factors required for understanding VPD and the lessons learned from previous studies. Then, we will review the components of a thorough VPD surveillance portfolio, and learn the importance of continued monitoring and communication of findings. For these objectives, we will use the example of the U.S. rotavirus vaccination program.

Step One: Understanding the Background: Burden and Risk Factors of VPD Illness and Transmission Processes of the Target Pathogen

An accurate quantitation of the burden of rotavirus illness represents more than simply an introduction to this particular pathogen. These “burden of disease” estimates are the scientific results that led to the understanding that this pathogen contributes substantially to childhood mortality and morbidity and impacts healthcare systems worldwide. Pre-vaccine era epidemiologic data formed the basis for creating meaningful surveillance systems that would come to fruition years later, when vaccines would be developed and introduced, and that would enable public health communities to assess the performance and impact of vaccines upon this VPD.

During the pre-vaccine era, rotavirus infected nearly every unvaccinated child before their fifth birthday. In the absence of vaccine, multiple rotavirus infections may occur during infancy and childhood. Rotavirus causes severe diarrhea and vomiting (acute gastroenteritis [AGE]), which can lead to dehydration, electrolyte depletion, complications of viremia, shock, and death. Nearly one-half million children around the world die of rotavirus infections each year, meaning that it is a significant source of mortality and morbidity among children globally [1].

Even in the United States and other developed countries, where rotavirus infections were much less likely to cause death, this virus was responsible for 40–50% of hospitalizations because of acute gastroenteritis during the winter months in the era before vaccines were introduced. Hundreds of thousands of emergency department (ED) and outpatient visits were a result of rotavirus as well, costing approximately $1 billion each year [2].

Meticulous studies describing how the virus infects humans and observations of when the most severe infections occurred were keys to determining when and how an effective vaccine would be developed and introduced. First rotavirus infections are most likely to result in moderate–severe cases of rotavirus gastroenteritis but subsequent infections are progressively milder. Velazquez et al. [3] found that the adjusted efficacy of a child's first natural rotavirus infection in protecting against subsequent natural rotavirus-associated diarrhea was 77%. This protection increased to 83% after two natural infections and to 92% after three natural infections. A 3-year study compared rotavirus-infected neonates with uninfected neonates. A similar proportion of neonatally infected and uninfected infants had rotavirus infections during the follow-up period. Symptoms among those neonatally infected, however, were less frequent and less severe leading to the conclusion that neonatal rotavirus infection protects against clinically severe disease during reinfection [4]. A similar finding was reported among a sample of Indian neonates infected in healthcare settings, most of whom had asymptomatic infections, resulting in a protective effect against rotavirus gastroenteritis lasting throughout the 2-year follow-up period, with protection concentrated in the first year of life [5].

The rationale for developing and implementing a vaccination program against rotavirus derived from observations that control measures, such as clean-water initiatives and improvements to personal hygiene, led to dramatic declines in bacterial and parasitic gastroenteritis infections across the world, but rates of rotavirus infection and illness among children in industrialized and less-developed countries remained similar [6–11]. Hygienic measures were unlikely to lead to corresponding declines in rotavirus burden [12]. Because first infections have been shown to induce strong immunity against severe rotavirus reinfections [3] and because vaccination mimics such first infections without causing illness, vaccination was identified as the optimal strategy for decreasing the burden associated with severe and fatal rotavirus diarrhea.

Any changes that may be later attributed to vaccination effects require knowledge of the pre-licensure (i.e., baseline) rates and trends in the target disease as a reference. Baseline data gives public health practitioners the grounding needed to quantitate the extent of observations (whether these are changes in hospital stays attributed to the VPD, mortality rates in a given age group, or other relevant measurements) after the vaccine is being used widely and helps delineate whether any post-licensure changes are likely due to the vaccine or are part of another underlying trend. Efforts to obtain baseline data are necessary before a vaccine is licensed and introduced [13].

Through an understanding of these epidemiological dynamics, VPD surveillance systems would later be able to track the correct clinical settings, clinical characteristics, transmission patterns, and the most likely ages of potential severe infections. This data, in turn, allows accurate assessments of the impact and performance of vaccines in childhood populations.

Step Two: Understanding the Vaccines

VPD surveillance activities should be tailored to an understanding of the vaccines to be assessed and the mechanisms of immunologic protection, as well as the studied and approved parameters by which the vaccines are administered.

During the pre-licensure clinical trial studies that are conducted prior to a vaccine's approval for widespread use, extensive data is collected regarding the vaccine's performance in controlled environments, its safety, and other factors that may influence when and how the vaccine is administered. These other factors may include assessments of the ideal age for vaccination and how many vaccine doses are needed to induce an acceptable level of immunity. Early phases of clinical trial (Phase II) may even indicate the best anatomic location for an intramuscular vaccine, dose-ranging studies, or whether an adjuvant improves the immunologic response against a particular antigen in the vaccine.

Using our example of rotavirus vaccines, very large pre-licensure clinical trials indicated that rotavirus vaccines are safe and are not associated with severe vaccine adverse events [14–16]. Rotavirus vaccines are orally administered, live-attenuated vaccines designed for infant immunization in order to avoid the most severe rotavirus infections expected to occur in the first months of life. Following licensure by the Food and Drug Administration (FDA), in February, 2006, a pentavalent (five-strain containing) human-bovine reassortant rotavi...

Table of contents

• Cover
• Table of Contents
• Title page
• Copyright page
• List of Contributors
• Foreword
• Preface
• Acknowledgments
• Acronyms and Abbreviations
• SECTION I: Introduction to Infectious Disease Surveillance
• SECTION II: Specific Surveillance Systems
• SECTION III: Methods Used in Surveillance and Data Analysis
• SECTION IV: Cross-Cutting Issues in Infectious Disease Surveillance
• Index
• End User License Agreement