In China, 87% of confirmed cases were ages 30 to 79 years and 3% were ages 80 years or older. Approximately 51% of patients were male.
In Italy, the median age and prevalence of comorbidities was higher compared with China.
In the UK, the median age of patients was 73 years and males accounted for 60% of admissions in a prospective observational cohort study of more than 20,000 hospitalized patients.
In the US, older patients (ages ≥65 years) accounted for 31% of all cases, 45% of hospitalizations, 53% of intensive care unit admissions, and 80% of deaths, with the highest incidence of severe outcomes in patients ages ≥85 years. Cases in children, adolescents, and young adults increased between October to December 2020; however, hospitalizations, intensive care unit admissions, and deaths remain low for these groups (2.5%, 0.8%, and <0.1% respectively, based on available data).
Evidence suggests that children have a lower susceptibility to infection compared with adults, with an odds ratio of 0.56 for being an infected contact compared with adults. Adolescents appear to have similar susceptibility to adults.
China - 2.1% (median age 7 years)
Italy - 1.2% (median age 4 to 5 years; higher in males but not statistically significant)
Spain - 0.8% (median age 3 years)
US - 12.6% (or 3336 cases per 100,000 children in the population) as of 14 January 2021.
In the UK, a prospective observational cohort study found that children and young adults represented 0.9% of all hospitalized patients at the time. The median age of children admitted to hospital was 4.6 years, 56% were male, 35% were under 12 months of age, and 42% had at least one comorbidity. In terms of ethnicity, 57% were White, 12% were South Asian, and 10% were Black. Age under 1 month, age 10 to 14 years, and Black race were risk factors for admission to critical care.
In the US, a retrospective cohort study of over 135,000 children found that the mean age of infected children was 8.8 years, and 53% were male. In terms of ethnicity, 59% were White, 15% were Black, 11% were Hispanic, and 3% were Asian. Only 4% of children tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in this population, and clinical manifestations were typically mild.
Most cases in children are from familial clusters, or children who have a history of close contact with an infected patient. It is rare for children to be the index case in household transmission clusters. Unlike adults, children do not seem to be at higher risk for severe illness based on age or sex.
A meta-analysis of over 2500 pregnant women with confirmed COVID-19 found that 73.9% of women were in the third trimester; 50.8% were from Black, Asian, or minority ethnic groups; 38.2% were obese; and 32.5% had chronic comorbidities.
In the UK, the estimated incidence of admission to hospital with confirmed SARS-CoV-2 infection in pregnancy is 4.9 per 1000 maternities. Most women were in the second or third trimester. Of these patients, 41% were ages 35 years or older, 56% were from Black or other ethnic minority groups, 69% were overweight or obese, and 34% had preexisting comorbidities.
In the US, 55,154 cases have been reported in pregnant women (as of 11 January 2021), with 9778 hospitalizations and 66 deaths. According to an analysis of approximately 400,000 women ages 15 to 44 years with symptomatic disease, Hispanic and non-Hispanic Black pregnant women appear to be disproportionately affected during pregnancy.
The incidence of infection in healthcare workers ranged from 0% to 49.6% (by polymerase chain reaction), and the prevalence of SARS-CoV-2 seropositivity ranged from 1.6% to 31.6%. The wide ranges are likely related to differences in settings, exposures, rates of community transmission, symptom status, use of infection control measures, and other factors.
A systematic review and meta-analysis of nearly 130,000 healthcare workers estimated the overall seroprevalence of SARS-CoV-2 antibodies to be 8.7%, with higher seroprevalence reported in North America (12.7%) compared with Europe (8.5%), Africa (8.2%), and Asia (4%). Risk factors for seropositivy included male sex; Black, Asian, or Hispanic ethnicity; working in a COVID-19 unit; patient-facing work; and frontline healthcare work.
Approximately 14% of the cases reported to the World Health Organization are in healthcare workers (range 2% to 35%).
The majority of healthcare workers with COVID-19 reported contact in the healthcare setting. In a study of over 9000 cases reported in healthcare workers in the US, 55% had contact only in a healthcare setting, 27% only in a household, 13% only in the community, and 5% in more than one setting.
The most frequently affected healthcare workers were nurses. Only 5% of healthcare workers developed severe disease and 0.5% died. The incidence of severe or critical disease and mortality in healthcare workers was lower than the incidence of severe or critical disease and mortality in all patients.
Patient-facing healthcare workers were three times more likely to be admitted to hospital compared with nonpatient-facing workers according to a study in Scotland. In the same study, healthcare workers and their household members accounted for 17% of hospitalizations.
Analysis of hospitalization data from 13 sites in the US found that 6% of hospitalized adults were healthcare workers, and 36% of these people were in nursing-related roles. Around 90% of hospitalized healthcare workers had at least one underlying condition, the most common conditions being obesity, hypertension, and diabetes.
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