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Review
. 2020 May 25;5(1):42.
doi: 10.1038/s41541-020-0193-6. eCollection 2020.

Certainty of success: three critical parameters in coronavirus vaccine development

David C Kaslow  1
Affiliations
Review

Certainty of success: three critical parameters in coronavirus vaccine development

David C Kaslow. NPJ Vaccines. .

Abstract

Vaccines for 17 viral pathogens have been licensed for use in humans. Previously, two critical biological parameters of the pathogen and the host-pathogen interaction-incubation period and broadly protective, relative immunogenicity-were proposed to account for much of the past successes in vaccine development, and to be useful in estimating the "certainty of success" of developing an effective vaccine for viral pathogens for which a vaccine currently does not exist. In considering the "certainty of success" in development of human coronavirus vaccines, particularly SARS-CoV-2, a third, related critical parameter is proposed-infectious inoculum intensity, at an individual-level, and force of infection, at a population-level. Reducing the infectious inoculum intensity (and force of infection, at a population-level) is predicted to lengthen the incubation period, which in turn is predicted to reduce the severity of illness, and increase the opportunity for an anamnestic response upon exposure to the circulating virus. Similarly, successfully implementing individual- and population-based behaviors that reduce the infectious inoculum intensity and force of infection, respectively, while testing and deploying COVID-19 vaccines is predicted to increase the "certainty of success" of demonstrating vaccine efficacy and controlling SARS-CoV-2 infection, disease, death, and the pandemic itself.

Keywords: Vaccines; Viral infection.

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Conflict of interest statement

Competing interestsD.C.K. is an employee of PATH (a not-for-profit organization), has no financial interest in any for-profit organization, and declares no competing interests.

Figures

Fig. 1
Fig. 1. “Certainty of Success” of vaccine development as a function of incubation period and broadly protective, relative immunogenicity.
a Two-dimensional analysis of 29 major human viral pathogens based on incubation period (x-axis; time, in days or weeks, from exposure to clinical signs or symptoms) and broad, relative immunogenicity (y-axis; high, moderate or low—see reference for definition). The 17 viral pathogens for which vaccine efficacy have been established are depicted in boxes with gray backgrounds; those for which vaccine efficacy has yet to be established are depicted in ellipses with white backgrounds. The area of graph associated with higher “certainty-of-success” for vaccine development (light gray) and lower “certainty-of-success” (dark gray) are separated by a thick black line. (Reprinted from an open-access article licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. b Effect of low and high infectious inoculum intensity on the assessment of the “certainty-of-success” (CoS) of SARS-CoV-2 vaccines. Interval bar (white) reflect the uncertainty in the inherent broadly protective, relative immunogenicity (see Glossary of Key Terms) associated with SARS-CoV-2 natural infection. Double-headed arrow (white with black outline) reflects the effect of infectious inoculum intensity higher (light gray) and lower (dark gray) “certainty-of-success” for vaccine development.
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