Hospitalization of Infants and Children Aged 0–4 Years With Laboratory-Confirmed COVID-19

COVID-NET, 14 States, March 2020-February 2022

Kristin J. Marks, PhD; Michael Whitaker, MPH; Nickolas T. Agathis, MD; Onika Anglin, MPH; Jennifer Milucky, MSPH; Kadam Patel, MPH; Huong Pham, MPH; Pam Daily Kirley, MPH; Breanna Kawasaki, MPH; James Meek, MPH; Evan J. Anderson, MD; Andy Weigel, MSW; Sue Kim, MPH; Ruth Lynfield, MD; Susan L. Ropp, PhD; Nancy L. Spina, MPH; Nancy M. Bennett, MD; Eli Shiltz, MPH; Melissa Sutton, MD; H. Keipp Talbot, MD; Andrea Price; Christopher A. Taylor, PhD; Fiona P. Havers, MD

Disclosures

Morbidity and Mortality Weekly Report. 2022;71(11):429-436.

Discussion

Weekly COVID-19–associated hospitalization rates among U.S. infants and children aged 0–4 years have declined since the peak of January 8, 2022; however, peak rates during Omicron predominance were approximately five times those of the peak during Delta predominance. Similarly, ICU admission rates during Omicron predominance peaked at approximately 3.5 times the peak rate during Delta predominance. The proportion of hospitalized infants and children with severe illness during all variant periods of predominance, coupled with the potential for longer-term sequelae including multisystem inflammatory syndrome,^[6,7] highlight the importance of preventing COVID-19 among infants and children aged 0–4 years. Strategies to prevent COVID-19 among infants and young children are important and include vaccination of currently eligible populations^[2] such as pregnant women,^[3] family members, and caregivers of infants and young children.^[4]

The proportion of patients with codetections of RSV was higher during Delta predominance than Omicron predominance. RSV circulation was low during the first year of the pandemic (pre-Delta predominance). The pattern of RSV codetections during 2021–2022 correlated with trends in RSV circulation observed in other surveillance systems: RSV circulation increased during the summer and fall of 2021 (Delta predominance) and declined during Omicron predominance^††††.^[8] These limited data suggest that the surge in hospitalizations during Omicron predominance was not driven by coinfections. The highest proportion of hospitalized infants and children requiring ICU admission occurred during Delta predominance, and the lowest occurred during Omicron predominance. Although the proportion of hospitalized infants and children admitted to an ICU was higher during Delta predominance, the rate of pediatric ICU admissions during Omicron predominance was approximately 3.5 times as high as that during Delta predominance, driven by the overall higher disease incidence.

Throughout the pandemic, infants aged <6 months have been hospitalized with laboratory-confirmed COVID-19 at higher rates than have infants and children aged 6 months–4 years. Infants aged <6 months were hospitalized with RSV codetections in higher proportions but required ICU admission and respiratory support in similar proportions to other age groups. Future studies are needed to understand the possible long-term consequences of COVID-19 infection among infants. Although infants aged <6 months are not currently eligible for vaccination, evidence suggests that this age group can receive protection through passive transplacental transfer of maternal antibodies acquired through vaccination.^[9] CDC recommends that women who are pregnant, breastfeeding, trying to become pregnant, or might become pregnant get vaccinated and stay up to date with COVID-19 vaccination.

The findings in this report are subject to at least four limitations. First, COVID-19–associated hospitalizations and viral coinfections might have been missed because of testing practice differences and test availability; this analysis could not account for changes in viral testing practices over time. Second, periods of variant predominance are not exclusive to a given variant; other variants might be circulating while one predominates. Third, it was not possible to account for seasonality or changes in public health policies and treatment practices over time; for example, the proportion of ICU admissions might reflect changing hospital capacity during the period of variant predominance rather than disease severity. Finally, the COVID-NET catchment areas include approximately 10% of the U.S. population; thus, these findings might not be nationally generalizable.

Coinciding with Omicron predominance, COVID-19–associated hospitalization rates among infants and children aged 0–4 years reached the current highest level of the pandemic during early January 2022. All persons who are eligible for vaccination,^[2] including pregnant women,^[3] should receive and stay up to date with COVID-19 vaccination to reduce the risk for severe disease for themselves and others with whom they come into contact,^[10] including infants and children aged 0–4 years who are currently not eligible for vaccination.^[4]

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Acknowledgments
Joelle Nadle, Monica Napoles, Sherry Quach, Gretchen Rothrock, California Emerging Infections Program, Oakland, California; Nisha Alden, Isaac Armistead, Madelyn Lensing, Sarah McLafferty, Millen Tsegaye, Colorado Department of Public Health and Environment; Ann Basting, Tessa Carter, Maria Correa, Daewi Kim, Amber Maslar, Julie Plano, Kimberly Yousey-Hindes, Connecticut Emerging Infections Program, Yale School of Public Health, New Haven, Connecticut; Marina Bruck, Rayna Ceaser, Taylor Eisenstein, Emily Fawcett, Sabrina Hendrick, Johanna Hernandez, Asmith Joseph, Grayson Kallas, Stephanie Lehman, Jana Manning, Annabel Patterson, Allison Roebling, Suzanne Segler, Chandler Surell, Katelyn Ward, Hope Wilson, School of Medicine, Emory University, Georgia Emerging Infections Program, Georgia Department of Public Health, Veterans Affairs Medical Center, Foundation for Atlanta Veterans Education and Research, Atlanta, Georgia; Chloe Brown, Jim Collins, Justin Henderson, Shannon Johnson, Sierra Peguies-Khan, Alexander Kohrman, Lauren Leegwater, Val Tellez Nunez, Libby Reeg, Michigan Department of Health and Human Services; Alison Babb, Richard Danila, Kristen Ehresmann, Jake Garfin, Jennifer Gilbertson, Grace Hernandez, Melissa McMahon, Kieu My Phi, Jill Reaney, Sara Vetter, Xiong Wang, Minnesota Department of Health; Melissa Judson, Sunshine Martinez, Mark Montoya, Florent Nkouaga, Jasmyn Sanchez, Chad Smelser, Daniel Sosin, New Mexico Department of Health; Kathy M. Angeles, Molly Bleecker, Sarah Shrum Davis, Nancy Eisenberg, Emily B. Hancock, Sarah A. Khanlian, Sarah Lathrop, Wickliffe Omondi, Mayvilynne Poblete, Francesca Pacheco, Dominic Rudin, Yadira Salazar-Sanchez, New Mexico Emerging Infections Program; Jennifer Akpo, Celina Chavez, Murtada Khalifa, Alesia Reed, Yassir Talha, CDC Foundation, Atlanta, Georgia; New Mexico Department of Health; Grant Barney, Kerianne Engesser, Suzanne McGuire, Adam Rowe, New York State Department of Health; Sophrena Bushey, Christina Felsen, Maria Gaitan, Christine Long, Thomas Peer, Kevin Popham, University of Rochester School of Medicine and Dentistry, Rochester, New York; Julie Freshwater, Denise Ingabire-Smith, Ann Salvator, Rebekah Sutter, Ohio Department of Health; Sam Hawkins, Public Health Division, Oregon Health Authority; Kathy Billings, Katie Dyer, Anise Elie, Gail Hughett, Karen Leib, Tiffanie Markus, Terri McMinn, Danielle Ndi, Manideepthi Pemmaraju, Emmanuel Sackey, Vanderbilt University Medical Center, Nashville, Tennessee; Ian Buchta, Amanda Carter, Ryan Chatelain, Melanie Crossland, Andrea George, Andrew Haraghey, Mary Hill, Laine McCullough, Jake Ortega, Tyler Riedesel, Caitlin Shaw, Ashley Swain, Salt Lake County Health Department, Salt Lake City, Utah; Rainy Henry, Sonja Mali Nti-Berko, Robert W. Pinner, Alvin Shultz, CDC; Epidemiology Task Force, CDC COVID-19 Emergency Response Team; Elizabeth Daly, Council of State and Territorial Epidemiologists.

^†††† https://www.cdc.gov/surveillance/nrevss/rsv/natl-trend.html

Table 1. Demographic and clinical characteristics and outcomes among infants and children aged 0–4 years hospitalized with laboratory-confirmed COVID-19,* by variant predominance period — Coronavirus Disease 2019–Associated Hospitalization Surveillance Network, 14 states, ^† March 1, 2020–January 31, 2022
Characteristic	Variant predominant period, no. (%) of hospitalizations				P-value^§(Omicron versus pre-Delta)	P-value^§(Omicron versus Delta)
Characteristic	Total	Pre-Delta Mar 1, 2020–Jun 26, 2021	Delta Jun 27–Dec 18, 2021	Omicron Dec 19, 2021–Jan 31, 2022	P-value^§(Omicron versus pre-Delta)	P-value^§(Omicron versus Delta)
Total no. of hospitalized infants and children	2,562^¶	1,200^¶	790^¶	572^¶	NA	NA
Age group, yrs, median (IQR)	0.6 (0.1–1.0)	0.6 (0.1–1.1)	0.7 (0.1–1.1)	0.6 (0.1–1.0)	0.41	0.69
<6 months	1,137 (44.3)	547 (45.6)	338 (42.8)	252 (43.9)	0.46	0.76
6–23 months	772 (30.4)	345 (28.8)	247 (31.2)	180 (32.0)
2–4 years	653 (25.3)	308 (25.6)	205 (26.0)	140 (24.1)
Sex
Male	1,433 (56.1)	651 (54.4)	443 (56.3)	339 (58.2)	0.18	0.54
Female	1,129 (43.9)	549 (45.6)	347 (43.7)	233 (41.8)	0.18	0.54
Race/Ethnicity**
Hispanic	710 (28.8)	397 (32.9)	184 (24.2)	129 (27.5)	0.001	0.40
Black, non-Hispanic	719 (26.7)	347 (28.8)	219 (27.5)	153 (23.1)
White, non-Hispanic	767 (29.9)	283 (23.5)	278 (34.6)	206 (34.1)
Asian or other Pacific Islander, non-Hispanic	154 (6.0)	76 (6.5)	45 (5.6)	33 (5.7)
Persons of all other races^††	65 (2.8)	32 (2.7)	16 (2.2)	17 (3.4)
Unknown race/ethnicity	147 (5.8)	65 (5.5)	48 (5.9)	34 (6.1)
Primary reason for admission^§§
Likely COVID-19–related	2,068 (84.7)	874 (80.5)	709 (90.0)	485 (84.8)	0.06	0.009
COVID-19–related symptoms at admission^¶¶
Yes	2,217 (86.6)	1,000 (83.6)	715 (90.8)	502 (86.9)	0.13	0.04
Underlying medical conditions
One or more underlying medical condition***	923 (35.8)	412 (34.6)	291 (36.8)	220 (36.6)	0.45	0.95
Prematurity^†††	294 (15.5)	120 (13.3)	100 (17.0)	74 (17.1)	0.10	0.95
Neurologic disorders	270 (10.3)	134 (11.0)	76 (9.5)	60 (10.0)	0.56	0.78
Chronic lung disease, including asthma	202 (7.7)	93 (7.9)	74 (9.4)	35 (5.8)	0.13	0.02
Congenital heart disease	152 (6.3)	62 (5.2)	41 (5.2)	49 (8.6)	0.01	0.02
Immunocompromised condition	81 (3.2)	40 (3.3)	23 (2.9)	18 (3.2)	0.92	0.83
Chronic lung disease of prematurity/BPD	64 (2.5)	27 (2.3)	19 (2.5)	18 (2.6)	0.67	0.86
Abnormality of airway	63 (2.3)	40 (3.4)	12 (1.5)	11 (1.4)	0.01	0.91
Chronic metabolic disease	61 (2.3)	31 (2.5)	15 (1.8)	15 (2.5)	0.95	0.39
Viral codetection^§§§
RSV	154 (9.5)	9 (1.6)	115 (19.7)	30 (7.3)	<0.001	<0.001
Influenza	11 (0.7)	1 (0.2)	3 (0.5)	7 (1.3)	0.02	0.16
Rhinovirus/Enterovirus	203 (17.0)	66 (15.1)	103 (25.8)	34 (10.7)	0.10	<0.001
Other viral infection	103 (8.8)	30 (6.5)	45 (11.2)	28 (9.0)	0.23	0.35
Hospitalization outcome^¶¶¶
Length of hospital stay, days, median (IQR)	1.5 (1–3.0)	1.5 (1–3.5)	2 (1–3.5)	1.5 (0.5–2.5)	0.001	0.002
ICU admission	624 (23.9)	290 (24.0)	210 (26.7)	124 (21.0)	0.19	0.02
BiPAP/CPAP	172 (6.5)	69 (5.9)	72 (9.1)	31 (5.1)	0.53	0.008
High flow nasal cannula	341(13.3)	98 (8.3)	159 (20.4)	84 (13.4)	0.002	0.002
Invasive mechanical ventilation	146 (5.7)	77 (6.4)	40 (5.2)	29 (5.2)	0.39	0.96
In-hospital death	16 (0.6)	10 (0.8)	4 (0.5)	2 (0.5)	0.51	0.99

Abbreviations: BiPAP/CPAP = bilevel positive airway pressure/continuous positive airway pressure; BPD = bronchopulmonary dysplasia; COVID-NET = Coronavirus Disease 2019–Associated Hospitalization Surveillance Network; ICU = intensive care unit; NA = not applicable; RSV = respiratory syncytial virus.
*Data are from a weighted sample of hospitalized infants and children with completed medical record abstractions. Sample sizes presented are unweighted with weighted percentages.
^†Includes persons admitted to a hospital with an admission date during March 1, 2020–January 31, 2022. Maryland contributed data through November 26, 2021. Counties included in COVID-NET surveillance: California (Alameda, Contra Costa, and San Francisco counties); Colorado (Adams, Arapahoe, Denver, Douglas, and Jefferson counties); Connecticut (Middlesex and New Haven counties); Georgia (Clayton, Cobb, DeKalb, Douglas, Fulton, Gwinnett, Newton, and Rockdale counties); Iowa (one county represented); Maryland (Allegany, Anne Arundel, Baltimore, Baltimore City, Calvert, Caroline, Carroll, Cecil, Charles, Dorchester, Frederick, Garrett, Harford, Howard, Kent, Montgomery, Prince George's, Queen Anne's, St. Mary's, Somerset, Talbot, Washington, Wicomico, and Worcester counties); Michigan (Clinton, Eaton, Genesee, Ingham, and Washtenaw counties); Minnesota (Anoka, Carver, Dakota, Hennepin, Ramsey, Scott, and Washington counties); New Mexico (Bernalillo, Chaves, Doña Ana, Grant, Luna, San Juan, and Santa Fe counties); New York (Albany, Columbia, Genesee, Greene, Livingston, Monroe, Montgomery, Ontario, Orleans, Rensselaer, Saratoga, Schenectady, Schoharie, Wayne, and Yates counties); Ohio (Delaware, Fairfield, Franklin, Hocking, Licking, Madison, Morrow, Perry, Pickaway and Union counties); Oregon (Clackamas, Multnomah, and Washington counties); Tennessee (Cheatham, Davidson, Dickson, Robertson, Rutherford, Sumner, Williamson, and Wilson counties); and Utah (Salt Lake county).
^§Proportions between the Omicron and Delta and Omicron and pre-Delta predominance periods were compared using chi-square tests, and medians were compared using Wilcoxon rank-sum tests; p-values <0.05 were considered statistically significant.
^¶Data are missing for <6% of observations for all variables, except for viral codetections.
**If ethnicity was unknown, non-Hispanic ethnicity was assumed.
^††Includes non-Hispanic persons reported as other or multiple races.
^§§Primary reason for admission was collected beginning June 1, 2020; hospitalizations before June 1, 2020, are excluded. Among sampled patients, COVID-NET collects data on the primary reason for admission to differentiate hospitalizations of patients with laboratory-confirmed SARS-CoV-2 infection who are likely admitted primarily for COVID-19 illness versus other reasons. During chart review, if the surveillance officer finds that the chief complaint or history of present illness mentions fever/respiratory illness, COVID-19–like illness, or a suspicion for COVID-19, then the case is categorized as COVID-19–related illness as the primary reason for admission. Reasons for admission that are likely primarily not COVID-19–related include categories such as inpatient surgery or trauma. Infants diagnosed with COVID-19 during their birth hospitalization were not categorized as likely COVID-19–related unless they exhibited COVID-19–related symptoms.
^¶¶COVID-19–related symptoms included respiratory symptoms (congested/runny nose, cough, hemoptysis/bloody sputum, shortness of breath/respiratory distress, sore throat, upper respiratory infection, influenza-like illness, and wheezing) and non-respiratory symptoms (abdominal pain, altered mental status/confusion, anosmia/decreased smell, chest pain, conjunctivitis, diarrhea, dysgeusia/decreased taste, fatigue, fever/chills, headache, muscle aches/myalgias, nausea/vomiting, rash, and seizures, and among those aged <2 years: apnea, cyanosis, decreased vocalization/stridor, dehydration, hypothermia, inability to eat/poor feeding, and lethargy). Symptoms are abstracted from the medical chart and might be incomplete.
***Defined as one or more of the following: chronic lung disease, chronic metabolic disease, blood disorder/hemoglobinopathy, cardiovascular disease, neurologic disorder, immunocompromised condition, renal disease, gastrointestinal/liver disease, rheumatologic/autoimmune/inflammatory condition, obesity, feeding tube dependency, or wheelchair dependency.
^†††Prematurity as an underlying medical condition is only reported for infants and children aged <2 years.
^§§§Results reported among infants and children who had testing performed (as opposed to all hospitalized infants and children). Because of testing practices, denominators differed among the viral respiratory pathogens: 1,582 infants and children were tested for RSV, 1,644 for influenza (influenza A, influenza B, flu [not subtyped]), 1,109 for rhino/enterovirus, and 1,120 for other viruses (adenovirus, parainfluenza 1, parainfluenza 2, parainfluenza 3, parainfluenza 4, human metapneumovirus).
^¶¶¶Hospitalization outcomes are not mutually exclusive; patients could be included in more than one category.

Table 2. Clinical characteristics and outcomes among infants and children aged 0–4 years hospitalized with laboratory-confirmed COVID-19 (N = 572),* by age group, during Omicron predominance — COVID-NET, 14 states, ^† December 19, 2021–January 31, 2022
Characteristic	No. (%) of hospitalizations, by age group				P-value^§
Characteristic	Total	<6 mos	6–23 mos	2–4 yrs	P-value^§
Total no. of hospitalized infants and children	572 (100)^¶	252 (44)^¶	180 (32)^¶	140 (24)^¶	NA
Primary reason for admission**
Likely COVID-19–related	485 (84.8)	210 (83.3)	159 (89.2)	116 (81.8)	0.23
COVID-19–related symptoms at admission^††
Yes	502 (86.9)	211 (82.0)^§§	163 (91.9)	128 (89.2)	0.04
Symptoms at admission
Fever/chills	340 (60.3)	128 (51.0)	123 (70.8)	89 (63.2)	0.001
Cough	317 (55.6)	119 (45.6)	120 (70.8)	78 (53.7)	<0.001
Congested/Runny nose	290 (52.1)	135 (51.3)	98 (61.1)	57 (41.6)	0.01
Shortness of breath/Respiratory distress	201 (34.7)	85 (31.0)	74 (43.8)	42 (29.3)	0.02
Inability to eat/Poor feeding	139 (29.2)	75 (26.6)	64 (32.6)	—^¶¶	0.21
Nausea/Vomiting	148 (26.6)	40 (18.1)	59 (31.8)	49 (35.4)	0.003
Fatigue	83 (13.4)	21 (6.6)	25 (13.7)	37 (25.2)	<0.001
Decreased vocalization/Stridor	49 (11.6)	15 (5.8)	34 (19.7)	—^¶¶	<0.001
Seizures	27 (3.9)	4 (1.5)	9 (5.0)	14 (6.9)	0.02
Underlying medical condition
One or more underlying medical condition***	220 (36.6)	66 (26.3)	80 (40.3)	74 (50.4)	<0.001
Prematurity	74 (17.1)	39 (16.7)	35 (17.7)	—^¶¶	0.83
Neurologic disorders	60 (10.0)	10 (3.6)	17 (8.9)	33 (23.0)	<0.001
Congenital heart disease	49 (8.6)	18 (7.1)	19 (9.2)	12 (10.5)	0.62
Chronic lung disease, including asthma	35 (5.8)	5 (2.5)	12 (5.3)	18 (12.6)	<0.001
Immunocompromised condition	18 (3.2)	1 (0.5)	5 (1.9)	12 (9.7)	<0.001
Chronic lung disease of prematurity/BPD	18 (2.6)	4 (1.8)	7 (2.6)	7 (4.3)	0.32
Chronic metabolic disease	15 (2.5)	2 (0.7)	5 (2.8)	8 (5.3)	0.02
Abnormality of airway	11 (1.4)	4 (1.2)	5 (1.8)	2 (1.3)	0.85
Viral codetection^†††
RSV	30 (7.3)	22 (12.7)	6 (4.3)	2 (2.0)	0.003
Influenza	7 (1.3)	4 (1.3)	1 (0.8)	2 (2.1)	0.62
Rhinovirus/Enterovirus	34 (10.7)	13 (10.6)	10 (8.4)	11 (13.5)	0.59
Other viral infections	28 (9.0)	4 (3.2)	14 (13.4)	10 (12.2)	0.03
Hospitalization outcome^§§§
Length of hospital stay, days, median (IQR)	1.5 (0.5–2.5)	1.5 (1–2.5)	1.5 (0.5–3)	1.5 (0.5–3)	0.70
ICU admission	124 (21.0)	57 (21.6)	39 (21.9)	28 (18.9)	0.81
BiPAP/CPAP	31 (5.1)	12 (4.5)	12 (6.1)	7 (4.8)	0.76
High flow nasal cannula	84 (13.4)	43 (14.1)	28 (16.1)	13 (8.7)	0.20
Invasive mechanical ventilation	29 (5.2)	10 (4.6)	11 (5.9)	8 (5.6)	0.84
In-hospital death	2 (0.5)	2 (1.1)	0 (—)	0 (—)	0.70

Abbreviations: BiPAP/CPAP = bilevel positive airway pressure/continuous positive airway pressure; BPD = bronchopulmonary dysplasia; COVID-NET = Coronavirus Disease 2019–Associated Hospitalization Surveillance Network; ICU = intensive care unit; NA = not applicable; RSV = Respiratory syncytial virus.
*Data are from a weighted sample of hospitalized infants and children with completed medical record abstractions. Sample sizes presented are unweighted with weighted percentages.
^†Includes persons admitted to a hospital with an admission date during December 19, 2021–January 31, 2022. Counties included in COVID-NET surveillance during this period: California (Alameda, Contra Costa, and San Francisco counties); Colorado (Adams, Arapahoe, Denver, Douglas, and Jefferson counties); Connecticut (Middlesex and New Haven counties); Georgia (Clayton, Cobb, DeKalb, Douglas, Fulton, Gwinnett, Newton, and Rockdale counties); Iowa (one county represented); Michigan (Clinton, Eaton, Genesee, Ingham, and Washtenaw counties); Minnesota (Anoka, Carver, Dakota, Hennepin, Ramsey, Scott, and Washington counties); New Mexico (Bernalillo, Chaves, Doña Ana, Grant, Luna, San Juan, and Santa Fe counties); New York (Albany, Columbia, Genesee, Greene, Livingston, Monroe, Montgomery, Ontario, Orleans, Rensselaer, Saratoga, Schenectady, Schoharie, Wayne, and Yates counties); Ohio (Delaware, Fairfield, Franklin, Hocking, Licking, Madison, Morrow, Perry, Pickaway and Union counties); Oregon (Clackamas, Multnomah, and Washington counties); Tennessee (Cheatham, Davidson, Dickson, Robertson, Rutherford, Sumner, Williamson, and Wilson counties); and Utah (Salt Lake county).
^§Proportions of infants and children aged <6 months, 6–23 months, and 2–4 years were compared using chi-square tests, and medians were compared using the Wilcoxon rank-sum test; p-values <0.05 were considered statistically significant.
^¶Data are missing for <6% of observations for all variables, except for viral codetections.
**Among sampled patients, COVID-NET collects data on the primary reason for admission to differentiate hospitalizations of patients with laboratory-confirmed SARS-CoV-2 infection who are likely admitted primarily for COVID-19 illness versus other reasons. During chart review, if the surveillance officer found that the chief complaint or history of present illness mentions fever/respiratory illness, COVID-19–like illness, or a suspicion for COVID-19, then the case was categorized as COVID-19–related illness as the primary reason for admission. Reasons for admission that are likely primarily not COVID-19–related include categories such as inpatient surgery or trauma. Infants with COVID-19 diagnosed during their birth hospitalization were not categorized as likely COVID-19–related unless they exhibited COVID-19–related symptoms.
^††COVID-19–related symptoms included respiratory symptoms (congested/runny nose, cough, hemoptysis/bloody sputum, shortness of breath/respiratory distress, sore throat, upper respiratory infection, influenza-like illness, and wheezing) and non-respiratory symptoms (abdominal pain, altered mental status/confusion, anosmia/decreased smell, chest pain, conjunctivitis, diarrhea, dysgeusia/decreased taste, fatigue, fever/chills, headache, muscle aches/myalgias, nausea/vomiting, rash, and seizures, and among those aged <2 years: apnea, cyanosis, decreased vocalization/stridor, dehydration, hypothermia, inability to eat/poor feeding, and lethargy). Symptoms are abstracted from the medical chart and might be incomplete.
^§§Among the 250 hospitalizations among infants aged <6 months with complete data on birth hospitalization, 14% (31 of 250) were birth hospitalizations. Of these birth hospitalizations, 91% (28 of 31) had no symptoms recorded. If birth hospitalizations are excluded, 94% (208 of 219) infants aged <6 months had symptoms recorded.
^¶¶Cyanosis, decreased vocalization/stridor, inability to eat/poor feeding, and lethargy are symptoms that are only recorded for infants and children aged <2 years. Prematurity is an underlying medical condition only reported for infants and children aged <2 years.
***Defined as one or more of the following: chronic lung disease, chronic metabolic disease, blood disorder/hemoglobinopathy, cardiovascular disease, neurologic disorder, immunocompromised condition, renal disease, gastrointestinal/liver disease, rheumatologic/autoimmune/inflammatory condition, obesity, feeding tube dependency, or wheelchair dependency.
^†††Results reported among infants and children who had testing performed (as opposed to all hospitalized infants and children). Because of differing testing practices, denominators differed among the viral respiratory pathogens: 424 infants and children were tested for RSV, 440 for influenza (influenza A, influenza B, flu [not subtyped]), 260 for rhino/enterovirus, and 261 for other viruses (adenovirus, parainfluenza 1, parainfluenza 2, parainfluenza 3, parainfluenza 4, and human metapneumovirus).
^§§§Hospitalization outcomes are not mutually exclusive; patients could be included in more than one category.

Authors and Disclosures

Kristin J. Marks, PhD^1,2, Michael Whitaker, MPH¹, Nickolas T. Agathis, MD^1,2, Onika Anglin, MPH^1,3, Jennifer Milucky, MSPH¹, Kadam Patel, MPH^1,3, Huong Pham, MPH¹, Pam Daily Kirley, MPH⁴, Breanna Kawasaki, MPH⁵, James Meek, MPH⁶, Evan J. Anderson, MD^7–9, Andy Weigel, MSW¹⁰, Sue Kim, MPH¹¹, Ruth Lynfield, MD¹², Susan L. Ropp, PhD¹³, Nancy L. Spina, MPH¹⁴, Nancy M. Bennett, MD¹⁵, Eli Shiltz, MPH¹⁶, Melissa Sutton, MD¹⁷, H. Keipp Talbot, MD¹⁸, Andrea Price¹⁹, Christopher A. Taylor, PhD¹ and Fiona P. Havers, MD¹, COVID-NET Surveillance Team

¹CDC COVID-19 Emergency Response Team; ²Epidemic Intelligence Service, CDC; ³General Dynamics Information Technology, Atlanta, Georgia; ⁴California Emerging Infections Program, Oakland, California; ⁵Colorado Department of Public Health and Environment; ⁶Connecticut Emerging Infections Program, Yale School of Public Health, New Haven, Connecticut; ⁷Emory University School of Medicine, Atlanta, Georgia; ⁸Georgia Emerging Infections Program, Georgia Department of Public Health; ⁹Atlanta Veterans Affairs Medical Center, Atlanta, Georgia; ¹⁰Iowa Department of Public Health; ¹¹Michigan Department of Health and Human Services; ¹²Minnesota Department of Health; ¹³New Mexico Department of Health; ¹⁴New York State Department of Health; ¹⁵University of Rochester School of Medicine and Dentistry, Rochester, New York; ¹⁶Ohio Department of Health; ¹⁷Public Health Division, Oregon Health Authority; ¹⁸Vanderbilt University Medical Center, Nashville, Tennessee; ¹⁹Salt Lake County Health Department, Salt Lake City, Utah.

Corresponding author
Kristin J. Marks, KJMarks@cdc.gov.

COVID-NET Surveillance Team
Jeremy Roland, California Emerging Infections Program; Jordan Surgnier, Colorado Department of Public Health and Environment; Carol Lyons, Connecticut Emerging Infections Program, Yale School of Public Health; Kyle Openo, Georgia Emerging Infections Program, Georgia Department of Health, Division of Infectious Diseases, Emory University School of Medicine; Kenzie Teno, Iowa Department of Health; Alexander Kohrman, Michigan Department of Health and Human Services; Erica Bye, Minnesota Department of Health; Cory Cline, New Mexico Department of Health; Alison Muse, New York State Department of Health; Virginia Cafferky, University of Rochester School of Medicine and Dentistry; Laurie Billing, Ohio Department of Health; Nasreen Abdullah, Public Health Division, Oregon Health Authority; William Schaffner, Vanderbilt University Medical Center; Keegan McCaffrey, Utah Department of Health

All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Evan J. Anderson reports grants from Pfizer, Merck, PaxVax, Micron, Sanofi-Pasteur, Janssen, MedImmune, and GlaxoSmithKline; personal fees from Pfizer, Medscape, Kentucky Bioprocessing, Inc., Sanofi-Pasteur, and Janssen, outside the submitted work; and institutional funding from the National Institutes of Health to conduct clinical trials of Moderna and Janssen COVID-19 vaccines. Eli Shiltz, Andy Weigel, Sue Kim, and Andrea Price report grants from the Council of State and Territorial Epidemiologists during the conduct of the study. Sue Kim reports grants from the Michigan Department of Health and Human Services during the conduct of the study. Ruth Lynfield reports editorial payments from the American Academy of Pediatrics Red Book (Committee on Infectious Diseases), which were donated to the Minnesota Department of Health. No other potential conflicts of interest were disclosed.