Evaluation of post-introduction COVID-19 vaccine effectiveness: Summary of interim guidance of the World Health Organization

Minal K. Patel, Isabel Bergeri, Joseph S. Bresee, Benjamin J. Cowling, Natasha S. Crowcroft, Kamal Fahmy, Siddhivinayak Hirve, Gagandeep Kang, Mark A. Katz, Claudio F. Lanata, Maïna L'Azou Jackson, Sudhir Joshi, Marc Lipsitch, Jason M. Mwenda, Francisco Nogareda, Walter A. Orenstein, Justin R. Ortiz, Richard Pebody, Stephanie J. Schrag, Peter G. SmithPadmini Srikantiah, Lorenzo Subissi, Marta Valenciano, David W. Vaughn, Jennifer R. Verani, Annelies Wilder-Smith, Daniel R. Feikin

Research output: Contribution to journalArticlepeer-review


Phase 3 randomized-controlled trials have provided promising results of COVID-19 vaccine efficacy, ranging from 50 to 95% against symptomatic disease as the primary endpoints, resulting in emergency use authorization/listing for several vaccines. However, given the short duration of follow-up during the clinical trials, strict eligibility criteria, emerging variants of concern, and the changing epidemiology of the pandemic, many questions still remain unanswered regarding vaccine performance. Post-introduction vaccine effectiveness evaluations can help us to understand the vaccine's effect on reducing infection and disease when used in real-world conditions. They can also address important questions that were either not studied or were incompletely studied in the trials and that will inform evolving vaccine policy, including assessment of the duration of effectiveness; effectiveness in key subpopulations, such as the very old or immunocompromised; against severe disease and death due to COVID-19; against emerging SARS-CoV-2 variants of concern; and with different vaccination schedules, such as number of doses and varying dosing intervals. WHO convened an expert panel to develop interim best practice guidance for COVID-19 vaccine effectiveness evaluations. We present a summary of the interim guidance, including discussion of different study designs, priority outcomes to evaluate, potential biases, existing surveillance platforms that can be used, and recommendations for reporting results.

Original languageEnglish (US)
Pages (from-to)4013-4024
Number of pages12
Issue number30
StatePublished - Jul 5 2021


  • COVID-19
  • Vaccination
  • Vaccine effectiveness

ASJC Scopus subject areas

  • Molecular Medicine
  • General Immunology and Microbiology
  • General Veterinary
  • Public Health, Environmental and Occupational Health
  • Infectious Diseases


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