There were 27,425 PICU admissions in Wisconsin with 294,577 associated diagnoses between 3/25/2015 and 12/31/2020 (Table 1). Despite an under-18 population decline of 0.4% annually [25], PICU admissions increased by 2.7% annually during the 5-year control epoch.
Table 1
Demographic Characteristic | Control Epoch 3/25/2015–3/24/2020 | COVID-2020 Epoch 3/25/2020–12/31/2020 |
Total admissions | 24,980 | 2,445 |
Total diagnoses | 266,528 | 28,049 |
Median age | 4.5 | 6.6 |
Sex | | |
Female | 11,000 (44%) | 1,127 (46%) |
Male | 13,980 (56%) | 1,318(54%) |
Race/ethnicity | | |
White | 15,276 (61%) | 1,501 (61%) |
Black or African American | 4,416 (18%) | 456 (19%) |
Hispanic or Latino | 1,906(8%) | 232 (9%) |
Asian | 503 (2%) | 61 (2%) |
Asian/Indian/Pacific Islander | 395 (2%) | 0 |
American Indian or Alaska Native | 362 (1%) | 34 (1%) |
Native Hawaiian or Other Pacific Islander | 30 (< 1%) | 5(< 1%) |
Other/Mixed | 541 (2%) | 61 (2%) |
Unspecified | 1551 (6%) | 95 (4%) |
In COVID-2020 there were 60 ± 9 total admissions per week compared to 103 ± 4 forecasted, RR 0.63 (95% CI: 0.59–0.68), p < 0.001. There were 17 ± 6 scheduled admissions per week in COVID-2020 compared to 28 ± 3 forecasted, RR 0.61 (95% CI: 0.55–0.67), p < 0.001, and there were 8 ± 5 respiratory viral admissions per week in COVID-2020 compared to 19 ± 9 forecasted, RR 0.40 (95% CI: 0.33–0.48), p < 0.001. For each category of interest in our primary hypothesis (total admissions, scheduled admissions, and respiratory viral admissions) the model-generated trend lines mirrored observed admissions during the control epoch (validating the model) but significantly exceeded observed admissions during COVID-2020 (Figs. 1–3).
Total weekly admissions (blue) with trend (black) are compared to a forecasted no-COVID admission trend from a quasi-Poisson model of weekly admissions regressed on an indicator for the COVID-19 pandemic, annual growth, a one-week lag, and harmonic terms to account for seasonality. The estimated rate ratio for the COVID-19 pandemic was 0.63 (95% CI: 0.59–0.68, p < 0.001), meaning that admissions during COVID-2020 were 37% lower than expected after accounting for annual growth and seasonality.
Weekly scheduled admissions (blue) with trend (black) are compared to a forecasted no-COVID admission trend from a quasi-Poisson model of admissions regressed on an indicator for the COVID-19 pandemic, a one-week lag, and harmonic terms to account for seasonality. The estimated rate ratio for the COVID-19 pandemic was 0.61 (95% CI: 0.55–0.67, p < 0.001) meaning that scheduled admissions during COVID-2020 were 39% lower than expected after accounting for seasonality.
Weekly respiratory viral admissions (blue) with trend (black) are compared to a forecasted no-COVID admission trend from a quasi-Poisson model of weekly admissions regressed on an indicator for the COVID-19 pandemic, annual growth, a one-week lag, and harmonic terms to account for seasonality. The estimated rate ratio for the COVID-19 pandemic was 0.40 (95% CI: 0.33–0.48, p < 0.001) meaning that respiratory viral admissions during COVID-2020 were 60% lower than expected after accounting for annual growth and seasonality.
Among other subcategories, admission rates and ratios associated with particular respiratory viruses are presented; there were precipitous reductions in respiratory syncytial virus, adenovirus, human metapneumovirus, enterovirus, and non-pandemic coronavirus admissions. Trauma admission rates were 4 ± 2 during COVID-2020, 6 ± 1 in the forecast [RR 0.73 (95% CI: 0.63–0.86), p < 0.001], and 4 ± 2 during the record low comparator period. Admissions with a diagnosis of interest were also less frequent than forecasted. The significance threshold was met for asthma exacerbation admissions [1 ± 1 vs. 5 ± 1, RR 0.28 (95% CI: 0.20–0.40), p < 0.001] and suicide/self-harm admissions [2 ± 2 vs. 4 ± 1, RR 0.59 (95% CI: 0.46–0.77), p < 0.001]. (Table 2)
Table 2
Admission Rates by Category
| | | | Comparison of Forecasted and COVID-2020 Rates |
Category | Record Low | Fore-casted | COVID − 2020 | Relative Rate | % Change | p |
Total Admissions | 86 ± 9 | 103 ± 4 | 60 ± 9 | 0.63 (0.59–0.68) | -37% | < 0.001 |
Scheduled Admissions | 23 ± 5 | 28 ± 3 | 17 ± 6 | 0.61 (0.55–0.67) | -39% | < 0.001 |
Respiratory Viral Admissions | 11 ± 5 | 19 ± 9 | 8 ± 5 | 0.40 (0.33–0.48) | -60% | < 0.001 |
Influenza | 0.2 ± 0.5 | 1 ± 1 | 0.02 ± 0.16 | 0.02 (0.00-0.42) | -98% | 0.012 |
Rhinovirus | 0 | 0.1 ± 0.0 | 0 | --- | --- | --- |
Non-pandemic coronavirus | 0 | 0.5 ± 0.0 | 0.02 ± 0.16 | 0.05 (0.01–0.47) | -95% | 0.009 |
Adenovirus | 0.5 ± 0.7 | 1.0 ± 0.0 | 0.5 ± 0.8 | 0.45 (0.26–0.78) | -55% | 0.005 |
Human metapneumovirus | 0.0 ± 0.2 | 1.0 ± 1.0 | 0.2 ± 0.8 | 0.21 (0.11–0.42) | -79% | < 0.001 |
RSV | 1 ± 2 | 3 ± 5 | 0.3 ± 1.1 | 0.08 (0.04–0.18) | -92% | < 0.001 |
Enterovirus | 0.1 ± 0.3 | 1.6 ± 0.0 | 0.7 ± 0.8 | 0.47 (0.29–0.77) | -53% | 0.003 |
Parainfluenza | 0.2 ± 0.5 | 1.1 ± 1.0 | 0.0 ± 0.2 | 0.02 (0.00-0.42) | -98% | 0.012 |
Trauma Admissions | 4 ± 2 | 6 ± 1 | 4 ± 2 | 0.73 (0.63–0.86) | -27% | < 0.001 |
Cardiovascular | 13 ± 3 | 15 ± 1 | 10 ± 4 | 0.67 (0.58–0.76) | -33% | < 0.001 |
Dermatologic | 0.1 ± 0.3 | 0.3 ± 0 | 0.0 ± 0.2 | 0.16 (0.04–0.67) | -84% | 0.014 |
Endocrine | 3 ± 2 | 5 ± 0 | 4 ± 2 | 0.78 (0.64–0.95) | -22% | 0.015 |
Factors influencing health | 0.0 ± 0.2 | 0.3 ± 0.0 | 0.3 ± 0.6 | 1.05 (0.61–1.81) | 5% | 0.865 |
Gastrointestinal | 2 ± 1 | 2 ± 0 | 2 ± 1 | 0.96 (0.72–1.27) | -4% | 0.766 |
Genetic | 1 ± 1 | 1 ± 0 | 1 ± 1 | 0.64 (0.45–0.91) | -36% | 0.013 |
Gynecologic | 0 | 0.0 ± 0.0 | 0.0 ± 0.2 | 1.60 (0.13–13.95) | 60% | 0.671 |
Hematologic | 0.4 ± 0.7 | 0.5 ± 0.0 | 0.6 ± 0.9 | 1.20 (0.79–1.83) | 20% | 0.394 |
Immunologic | 0 | 0.0 ± 0.0 | 0.0 ± 0.2 | 1.06 (0.13–8.45) | 6% | 0.957 |
Infectious | 4 ± 2 | 7 ± 1 | 5 ± 3 | 0.62 (0.50–0.78) | -38% | < 0.001 |
Injury/poisoning/adverse effects | 11 ± 3 | 12 ± 1 | 8 ± 3 | 0.73 (0.65–0.82) | -27% | < 0.001 |
Metabolic | 0.8 ± 0.7 | 1.0 ± 0.0 | 0.6 ± 0.8 | 0.66 (0.45–0.99) | -34% | 0.045 |
Neurologic | 9 ± 3 | 12 ± 0 | 7 ± 3 | 0.60 (0.51–0.70) | -40% | < 0.001 |
Newborn/perinatal | 0.2 ± 0.5 | 0.3 ± 0.0 | 0.2 ± 0.5 | 0.86 (0.44–1.68) | -14% | 0.654 |
Oncologic | 2 ± 2 | 3 ± 0 | 2 ± 1 | 0.74 (0.60–0.92) | -26% | 0.008 |
Ophthalmologic | 0 | 0.1 ± 0.0 | 0 | -- | -- | -- |
Orthopedic | 1 ± 1 | 1 ± 0 | 0 | 0.68 (0.43–1.07) | -32% | 0.094 |
Psychiatric | 0.1 ± 0.4 | 0.6 ± 0.0 | 0.4 ± 0.7 | 0.61 (0.31–1.19) | -39% | 0.151 |
Renal/genitourinary | 0.7 ± 0.8 | 1.2 ± 0.0 | 0.9 ± 1.0 | 0.73 (0.50–1.06) | -27% | 0.100 |
Respiratory and Respiratory/ENT | 23 ± 6 | 30 ± 5 | 12 ± 3 | 0.41 (0.35–0.47) | -59% | < 0.001 |
Rheumatologic | 0.1 ± 0.3 | 0.2 ± 0.0 | 0.4 ± 0.8 | 2.16 (1.12–4.15) | 216% | 0.022 |
Symptoms | 1 ± 1 | 2 ± 0 | 2 ± 2 | 1.09 (0.88–1.36) | 9% | 0.443 |
Transplant | 0.1 ± 0.3 | 0.3 ± 0.0 | 0.3 ± 0.5 | 0.86 (0.46–1.61) | -14% | 0.644 |
DKA | 3 ± 2 | 6 ± 0 | 4 ± 2 | 0.78 (0.64–0.95) | -22% | 0.014 |
Suicide/self-harm | 2 ± 2 | 4 ± 1 | 2 ± 2 | 0.59 (0.46–0.77) | -41% | < 0.001 |
Accidental ingestions | 1 ± 1 | 2 ± 0 | 1 ± 1 | 0.69 (0.48-1.00) | -31% | 0.053 |
Child abuse | 0.1 ± 0.3 | 0.3 ± 0.0 | 0.2 ± 0.4 | 0.72 (0.37–1.41) | -28% | 0.335 |
Asthma exacerbation | 4 ± 2 | 5 ± 1 | 1 ± 1 | 0.28 (0.20–0.40) | -72% | < 0.001 |
We compared admissions in the 40-week study epoch (3/25/2020–12/31/2020, COVID-2020), to those forecasted from the preceding five years’ data (3/25/2015–3/24/2020, the control epoch) using mean weekly admission rates with standard deviations and rate ratios with 95% confidence intervals. |
When we considered admissions according to the 23 mutually-exclusive VPS diagnostic categories based largely on body systems, the greatest reductions between observed and forecasted admissions occurred in respiratory/ENT [12 ± 3 vs. 30 ± 5, RR 0.41 (95% CI: 0.35–0.47), p < 0.001], neurologic [7 ± 3 vs. 12 ± 0, RR 0.60 (95% CI: 0.51–0.70), p < 0.001], and cardiovascular [10 ± 4 vs. 15 ± 1, RR 0.67 (95% CI: 0.58–0.76), p < 0.001] admissions. No category had significantly increased weekly admissions during COVID-2020. (Table 2)
Finally, 104 patients [96 children and 8 adults (age > 17 years)] with a COVID-19 diagnosis were admitted to PICUs in Wisconsin in 2020. All of the COVID-19 admissions occurred during COVID-2020, comprising 4.3% of the PICU admissions during the epoch. COVID-19 was the primary diagnosis in 36 of the 104 cases.