COVID-19 rising among children and young adults in Washington State

COVID-19 rising among children and young adults in Washington State

By Dr. Ananya Mandal, MDNov 17 2020

Researchers from the University of Washington, USA, and the Swedish Cancer Institute, Washington, USA, have found that between March and August 2020, the number of young adults and children infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Washington state rose. Their study titled, “Continued Age Shift of Confirmed Positive COVID-19 Incidence Over Time to Children and Young Adults: Washington State March – August 2020,” has been released on the preprint server medRxiv*.

Study: Continued Age Shift of Confirmed Positive COVID-19 Incidence Over Time to Children and Young Adults. Image Credit: creativeneko


Over 55.1 million people worldwide have been infected with SARS-CoV-2, the causative pathogen of coronavirus disease 2019 (COVID-19) – with over 11.2 million cases stemming from the United States alone. The first case was reported in Washington state on January 19, 2020. A statewide lockdown followed this on March 23, 2020, and this initial lockdown was extended until May 20.

From here on, the pandemic had passed its initial “peak,” the team writes. This led to a phased removal of restrictions that were earlier implemented to prevent SARS-CoV-2’s spread, resulting in increased activity among younger persons in the realm of non-essential work, social gatherings, travel etc.

During the lockdown, there was a decline in hospitalization rates and death rates among those who were older and with comorbid conditions; within these numbers, cases among the elderly plateaued and declined. However, the positive cases among the younger population rose as lockdown measures were eased. This study attempted to look at the age-related trends from the Washington State Department of Health (DOH) data in light of these developments.

Study design

This was a longitudinal study with data from the Washington State DOH. Participants were those with a confirmed case of COVID-19. The results of all tests were entered into the Washington Disease Reporting System (WDRS), an electronic disease surveillance system.

Their age-wise distribution was assessed from March-April 2020 and March-August 2020 for changes in proportions. The team obtained data including the number of cases, deaths and hospitalizations by week, county and age groups. Age groups assigned to the cases were:

  • 0-19 years
  • 20-39 years
  • 40-59 years
  • 60-79 years
  • Over 80 years


The researchers noted that between March 1 and April 19, 2020, case positivity for COVID-19 showed a 10 percent reduction in cases aged over 60 years. Conversely, there was a 20 percent rise in cases aged between 0 and 39 years.

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Overall results can be summarized as:

  • Chi-square test comparing ages 0 to 39 years and those over 60 years showed a statistically significant difference
  • The number of positive cases between January 16 and April 19 was 14,220, and the cases confirmed from March 1 to April 19 was 13,934
  • The number of cases over the study period ranging from 8 weeks showed:
    • 515 cases among those aged between 0 and 19 years
    • 4,078 cases among those aged between 20 and 39 years
    • 4,788 cases among those aged between 40 and 59 years
    • 3,221 cases among those aged between 60 and 79 years
    • 1,332 cases among those aged over 80 years
  • The four Washington counties with the highest number of cases were King (5,955 cases), Snohomish (2,300), Pierce (1,300), and Yakima (1,119).
  • After the first peak around March 22, the incidences fell among older adults, and the percentage of new cases rose by 20 percent and 40 percent among those below 19 years and those aged between 20 and 39 years, respectively
  • This rise among cases was despite the fact that more testing was done among older adults
  • Positive cases until August 2020 was around 60 percent among those aged below 40 years. The numbers rose to 19 percent among those less than 19 years old and rose to 42 percent among those aged between 20 and 39 years.
  • Between March 22 and April 19, COVID-19 hospitalization rates fell by 49 percent for those over the age of 40 years. There was also a 54 percent decline in new cases in this age group. The hospitalization rate among age 20-39-year-olds fell by 35 percent, and there was a 36 percent decline in new cases in this age group.

WA State DOH COVID-19 Confirmed Cases by Age: 3/1/2020-4/19/2020

Conclusions and implications

This study provides a rich case study which shows that the number of new cases of COVID-19 are increasing among children aged below 19 years and young adults aged between 20 and 39 years. The authors believe this could mean that the younger population could play a significant role in “propagating the epidemic by creating a reservoir of disease.” As other studies suggest similar trends with young adults across Europe, this study presents further empirical evidence to suggest that the activities of young people are increasingly governing SARS-CoV-2 transmission and its dynamics of spread.

Their infection could be a source of disease for vulnerable older persons, especially those with comorbidities. Authors write that media and public health messages should be age-appropriate and targeted towards “less vulnerable, more mobile and lower priority vaccination age groups” to reduce the incidence of COVID-19 in the whole population.

*Important Notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.


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