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. 2022 Feb 24;62(4):503–510. doi: 10.1016/j.amepre.2021.11.007

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© 2021 American Journal of Preventive Medicine. Published by Elsevier Inc.

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.

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Influence of cross-immunity between annual strains on second season influenza cases.

Note: Second-season cases per 100,000 are depicted by the burden of the first season (low versus normal) and by the amount of viral transmissibility (low versus high). x-axis is % cross-immunity between first- and second-year strains; y-axis is mean second season cases per 100,000. The shaded area represents 95% CIs of model results. Arrows indicate likely cross-immunity values for first-season/second-season strain pairs. For example, H1N1/H1N1 means that the first season and second season strains are both H1N1. The dashed line is second-season cases after a low first season. The solid line is second-season cases after a normal first season. The difference between dashed and solid lines indicates an increase in second-season cases when first-season cases are very low.