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. 2021 Mar 24;16(3):e0243042.
doi: 10.1371/journal.pone.0243042. eCollection 2021.

Continued proportional age shift of confirmed positive COVID-19 incidence over time to children and young adults: Washington State March-August 2020

Judith Malmgren  1 , Boya Guo  1 , Henry G Kaplan  2
Affiliations

Continued proportional age shift of confirmed positive COVID-19 incidence over time to children and young adults: Washington State March-August 2020

Judith Malmgren et al. PLoS One. .

Abstract

Background: As the coronavirus (COVID-19) epidemic passed initial infection peak in Washington State, phased re-opening lifted stay-at-home orders and restrictions leading to increased non-essential work, social activities and gathering, especially among younger persons.

Methods: A longitudinal cohort analysis of Washington State Department of Health COVID-19 confirmed case age distribution 1) March-April 2020 (N = 13,934) and 2) March-August 2020 (N = 76,032) for proportional change over time using chi square tests for significance.

Results: From March 1st to April 19, 2020 COVID-19 age distribution shifted with a 10% decline in cases age 60 years and older and a 20% increase in age 0-19/20-39 years (chi-square = 223.10, p < .001). Number of cases over the initial analysis period were 0-19 years n = 515, 20-39 years n = 4078, 40-59 years n = 4788, 60-79 years n = 3221, 80+ years n = 1332. After the peak (March 22, 2020), incidence declined in older age groups and increased among age 0-19 and 20-39 age groups from 20% to 40% of total cases by April 19 and 50% by May 3. During this time testing expanded with more testing among older age groups and less testing among younger age groups while case positivity shifted young. Percent positive cases age 0-19/20-39 years through August 2020 increased to a consistent average of 60% [age 0-19 increased to 19% (N = 10257), age 20-39 increased to 42% (N = 30215)].

Conclusions: An increased sustained proportion of COVID-19 incidence is present among children (age 0-19) and young adults (age 20-39) indicating an elevated role in disease spread during the epidemic creating a possible reservoir of disease with spillover risk to more vulnerable older persons and those with comorbid conditions. Media savvy age-appropriate messaging to enhance mitigation compliance among less vulnerable, more mobile and lower priority vaccination age groups will be a continued necessity and priority to reduce overall population incidence.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. WA State DOH COVID-19 confirmed cases by age: 3/1/2020-4/19/2020.
Fig 2
Fig 2. WA State DOH COVID-19 testing by age group: 3/1/2020-4/19/2020.
Fig 3
Fig 3. WA State DOH confirmed cases by age 3/1/2020-8/23/2020.
See this image and copyright information in PMC

References

    1. Holshue ML, DeBolt C, Lundquist S, et al.. Washington State 2019-nCoV Case Investigation Team. First case of 2019 novel coronavirus in the United States. N Engl J Med. 2020;382(10):929–936. 10.1056/NEJMoa2001191 - DOI - PMC - PubMed
    1. Governor of Washington, Proclamation by the Governor amending proclamation 20–05. https://www.governor.wa.gov/sites/default/files/proclamations/20-28.2%20.... Accessed May 5, 2020.
    1. Malmgren J, Guo B, Kaplan HG. COVID-19 Confirmed Case Incidence Age Shift to Young Persons Age 0–19 and 20–39 Years Over Time: Washington State March—April 2020. medRxiv 2020.05.21.20109389; 10.1101/2020.05.21.20109389 - DOI
    1. Personal communication with the Washington State Department of Health, State Public Health Lab, COVID-19 Branch Manager, Denny Russel. March 5, 2021
    1. CDC Has Fixed Issue Delaying Coronavirus Testing In U.S., Health Officials Say: Shots—Health News: NPR. https://www.npr.org/sections/health-shots/2020/02/27/809936132/cdc-fixes... Accessed March 5, 2021.

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