Case-control vaccine effectiveness studies: Preparation, design, and enrollment of cases and controls

Jennifer R Verani¹, Abdullah H Baqui², Claire V Broome³, Thomas Cherian⁴, Cheryl Cohen⁵, Jennifer L Farrar⁶, Daniel R Feikin⁷, Michelle J Groome⁸, Rana A Hajjeh⁶, Hope L Johnson⁹, Shabir A Madhi¹⁰, Kim Mulholland¹¹, Katherine L O'Brien¹², Umesh D Parashar⁶, Manish M Patel⁶, Laura C Rodrigues¹³, Mathuram Santosham¹², J Anthony Scott¹⁴, Peter G Smith¹⁵, Halvor Sommerfelt¹⁶, Jacqueline E Tate⁶, J Chris Victor¹⁷, Cynthia G Whitney⁶, Anita K Zaidi¹⁸, Elizabeth R Zell⁶

Affiliations

¹ National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, USA. Electronic address: jverani@cdc.gov.
² International Center for Maternal and Newborn Health, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St, Baltimore, MD, USA.
³ Rollins School of Public Health Emory University, 1518 Clifton Rd, Atlanta, GA, USA.
⁴ Department of Immunizations, Vaccines and Biologicals, World Health Organization, 20 Avenue Appia, 1211 Geneva, Switzerland.
⁵ Centre for Respiratory Diseases and Meningitis, National Institute for Communicable Diseases, 1 Modderfontein Road, Sandringham, Johannesburg, South Africa.
⁶ National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, USA.
⁷ National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, USA; International Vaccine Access Center, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St, Baltimore, MD, USA.
⁸ Respiratory and Meningeal Pathogens Unit, University of Witwatersrand, Richard Ward, 1 Jan Smuts Ave, Braamfontein, Johannesburg, South Africa.
⁹ Monitoring & Evaluation, Policy & Performance, GAVI Alliance, Chemin des Mines 2, 1202 Geneva, Switzerland.
¹⁰ Centre for Respiratory Diseases and Meningitis, National Institute for Communicable Diseases, 1 Modderfontein Road, Sandringham, Johannesburg, South Africa; Respiratory and Meningeal Pathogens Unit, University of Witwatersrand, Richard Ward, 1 Jan Smuts Ave, Braamfontein, Johannesburg, South Africa.
¹¹ Murdoch Children's Research Institute, Royal Children's Hospital, 50 Flemington Rd, Parkville, VIC 3052, Australia; Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK.
¹² International Vaccine Access Center, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St, Baltimore, MD, USA.
¹³ Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK.
¹⁴ Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK; KEMRI-Wellcome Trust Research Programme, P.O. Box 230-80108, Kilifi, Kenya.
¹⁵ MRC Tropical Epidemiology Group, London School of Tropical Medicine and Hygiene, London, UK.
¹⁶ Centre of Intervention Science in Maternal and Child Health and Centre for International Health, University of Bergen, P.O. Box 7800, Bergen, Norway; Department of International Public Health, Norwegian Institute of Public Health, PO Box 4404, Nydalen, Oslo, Norway.
¹⁷ PATH, 2201 Westlake Avenue, Seattle, WA, USA.
¹⁸ Aga Khan University, Stadium Rd, Karachi, Pakistan.

PMID: 28442231
PMCID: PMC7007298
DOI: 10.1016/j.vaccine.2017.04.037

Review

Case-control vaccine effectiveness studies: Preparation, design, and enrollment of cases and controls

Jennifer R Verani et al. Vaccine. 2017.

. 2017 Jun 5;35(25):3295-3302.

doi: 10.1016/j.vaccine.2017.04.037. Epub 2017 Apr 22.

Authors

Affiliations

¹ National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, USA. Electronic address: jverani@cdc.gov.
² International Center for Maternal and Newborn Health, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St, Baltimore, MD, USA.
³ Rollins School of Public Health Emory University, 1518 Clifton Rd, Atlanta, GA, USA.
⁴ Department of Immunizations, Vaccines and Biologicals, World Health Organization, 20 Avenue Appia, 1211 Geneva, Switzerland.
⁵ Centre for Respiratory Diseases and Meningitis, National Institute for Communicable Diseases, 1 Modderfontein Road, Sandringham, Johannesburg, South Africa.
⁶ National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, USA.
⁷ National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, USA; International Vaccine Access Center, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St, Baltimore, MD, USA.
⁸ Respiratory and Meningeal Pathogens Unit, University of Witwatersrand, Richard Ward, 1 Jan Smuts Ave, Braamfontein, Johannesburg, South Africa.
⁹ Monitoring & Evaluation, Policy & Performance, GAVI Alliance, Chemin des Mines 2, 1202 Geneva, Switzerland.
¹⁰ Centre for Respiratory Diseases and Meningitis, National Institute for Communicable Diseases, 1 Modderfontein Road, Sandringham, Johannesburg, South Africa; Respiratory and Meningeal Pathogens Unit, University of Witwatersrand, Richard Ward, 1 Jan Smuts Ave, Braamfontein, Johannesburg, South Africa.
¹¹ Murdoch Children's Research Institute, Royal Children's Hospital, 50 Flemington Rd, Parkville, VIC 3052, Australia; Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK.
¹² International Vaccine Access Center, Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe St, Baltimore, MD, USA.
¹³ Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK.
¹⁴ Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK; KEMRI-Wellcome Trust Research Programme, P.O. Box 230-80108, Kilifi, Kenya.
¹⁵ MRC Tropical Epidemiology Group, London School of Tropical Medicine and Hygiene, London, UK.
¹⁶ Centre of Intervention Science in Maternal and Child Health and Centre for International Health, University of Bergen, P.O. Box 7800, Bergen, Norway; Department of International Public Health, Norwegian Institute of Public Health, PO Box 4404, Nydalen, Oslo, Norway.
¹⁷ PATH, 2201 Westlake Avenue, Seattle, WA, USA.
¹⁸ Aga Khan University, Stadium Rd, Karachi, Pakistan.

PMID: 28442231
PMCID: PMC7007298
DOI: 10.1016/j.vaccine.2017.04.037

Abstract

Case-control studies are commonly used to evaluate effectiveness of licensed vaccines after deployment in public health programs. Such studies can provide policy-relevant data on vaccine performance under 'real world' conditions, contributing to the evidence base to support and sustain introduction of new vaccines. However, case-control studies do not measure the impact of vaccine introduction on disease at a population level, and are subject to bias and confounding, which may lead to inaccurate results that can misinform policy decisions. In 2012, a group of experts met to review recent experience with case-control studies evaluating the effectiveness of several vaccines; here we summarize the recommendations of that group regarding best practices for planning, design and enrollment of cases and controls. Rigorous planning and preparation should focus on understanding the study context including healthcare-seeking and vaccination practices. Case-control vaccine effectiveness studies are best carried out soon after vaccine introduction because high coverage creates strong potential for confounding. Endpoints specific to the vaccine target are preferable to non-specific clinical syndromes since the proportion of non-specific outcomes preventable through vaccination may vary over time and place, leading to potentially confusing results. Controls should be representative of the source population from which cases arise, and are generally recruited from the community or health facilities where cases are enrolled. Matching of controls to cases for potential confounding factors is commonly used, although should be reserved for a limited number of key variables believed to be linked to both vaccination and disease. Case-control vaccine effectiveness studies can provide information useful to guide policy decisions and vaccine development, however rigorous preparation and design is essential.

Keywords: Case-control studies; Evaluation studies; Vaccines.

Published by Elsevier Ltd.

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Conflict of interest statement

Author disclosures of potential conflict of interest

CC reports having received grant funds from Sanofi Pasteur that were awarded to the National Institute for Communicable Diseases, South Africa

References

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Case-control vaccine effectiveness studies: Preparation, design, and enrollment of cases and controls

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Case-control vaccine effectiveness studies: Preparation, design, and enrollment of cases and controls

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