Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2021 Aug 31;39(41):6088–6094. doi: 10.1016/j.vaccine.2021.08.098

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© 2021 Elsevier Ltd. All rights reserved.

Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

PMC Copyright notice

Fig. 1 — Schematic representation of the epidemiological model of Eqs. (1), (2), (3), (4), (5), (6), (7), (8), (9). The dashed-line arrows indicate that the V compartment is virtual, meaning that the individuals just pass through it.