Very low rates of severe COVID-19 in children hospitalised with confirmed SARS-CoV-2 infection in London, England”

Graphical abstract

We read with interest the publication by Chappell et al. reporting a very low risk of severe COVID in immunosuppressed children in England.¹

Compared to adults, children and young people (CYP) are more likely to remain asymptomatic or develop mild symptoms when exposed to SARS-CoV-2, and less likely to develop severe disease, be hospitalised, or die of COVID-19.² In adults, hospitalisation and case fatality rates due to COVID-19 are regularly used to measure disease severity with new variants and following vaccination.³ The disconnect between infection and severe disease after successful COVID-19 immunisation programmes, for example, has been a primary driver for many countries to remove mitigations even with the emergence of more transmissible variants.

In CYP, COVID-19 fatalities are rare and the use of COVID-19 hospitalisations as a proxy for disease severity,⁴ is questionable because of the high rates of incidental (asymptomatic or mild) infections identified during routine SARS-CoV-2 screening of all CYP presenting to hospital. Two years into the pandemic, there are still limited data on the risk of hospitalisation for severe COVID-19 in CYP. We, therefore, undertook a retrospective case-note review of CYP admitted to a large paediatric hospital in London with PCR-confirmed SARS-CoV-2 infection over 14-month period covering the alpha, delta and omicron variant waves (Fig. 1a and b ).

Fig. 1a.

Children and young people aged 0–18 years who were admitted to St. George's Hospital, London, with PCR-confirmed SARS-CoV-2 infection and total case numbers for the same age-group in London by month of year during December 2020 to January 2022. The blue bars denote children hospitalised for acute COVID-19, the orange bars denote hospitalisations where SARS-CoV-2 likely contributed to the hospitalisation and the grey bars denote incidental infections in children and young people hospitalised with other medical conditions.

Fig. 1b.

Children and young people aged 0–18 years who were admitted to St. George's Hospital, London, with PCR-confirmed SARS-CoV-2 infection by age-group during December 2020 to January 2022. The blue bars denote children hospitalised for acute COVID-19, the orange bars denote hospitalisations where SARS-CoV-2 likely contributed to the hospitalisation and the grey bars denote incidental infections in children and young people hospitalised with other medical conditions.

St. George's Hospital is a large teaching hospital providing acute paediatric A&E, general and specialist paediatric, oncological, surgical and neurosurgical, orthopaedic and trauma, NICU and PICU care for children in South London. CYP aged 0–18 years with a SARS-CoV-2 PCR-positive result between 01 December 2020 and 31 January 2022 were identified through the hospital microbiology laboratory database and their electronic medical records reviewed by two independent paediatricians. Case rates for 0–18-year-olds in London were obtained from national community testing data.⁵ We excluded children with PIMS-TS, which typically occurs 2–6 weeks after SARS-CoV-2 infection by which time SARS-CoV-2 PCR-tests are usually negative. Confirmed cases were categorised into:

• (i)Incidental: admitted for an unrelated illness, but SARS-CoV-2 PCR-positive on routine screening
• (ii)Contributory: SARS-CoV-2 potentially contributed to hospitalisation
• (iii)Severe COVID-19: SARS-CoV-2 was the primary reason for hospitalisation

During the 14-month period, there were 33,775 CYP A&E attendances and 3593 hospitalisations at St. George's Hospital. Of these, 147 were hospitalised with a positive SARS-CoV-2 PCR-test. The distribution of incidental and contributory cases closely followed community infection rates in London, but hospitalisations for severe COVID-19 occurred mainly during the alpha wave, with very few cases during the delta or omicron waves despite large numbers of community infections in the same age-group.

Incidental infections accounted for 83 (57%) cases and included CYP admitted for surgical (24/83, 29%), neurological (12/83, 14%), trauma (10/83, 12%) and other illnesses (e.g. eating disorders, neonatal jaundice; 37/83,45%). Cases where SARS-CoV-2 likely contributed to hospitalisation (49/147, 33%) had clinical presentations that were typical of other childhood viral illnesses. Most CYP (32/49, 65%) presented with fever and respiratory symptoms, or fever with inadequate oral intake, which warranted admission for observation and/or sepsis screen with antibiotic cover until bacterial cultures returned negative after 48 h; 26% (13/49) in this category were aged <3 months. Other presentations included acute exacerbation of asthma (7/49, 14%), febrile convulsions (4/49, 8%) and other presentations (e.g. diarrhoea and vomiting, feeding difficulties, lethargy; 6/49, 12%). Symptoms were generally mild and only five required supplemental oxygen during their short hospital stay.

Thus, only 15 children (10%) were hospitalised with severe COVID-19 presenting as pneumonitis, mainly during the alpha variant wave (10/15, 67%), and in older CYP (9/15 [60%] were aged 12–18 years) with comorbidities (11/15, including 8 with immunosuppression) (Table 1 ). Thirteen CYP required supplemental oxygen, seven required intensive care and all recovered.

Table 1.

Supplement Table. Characteristics, clinical presentation, management and outcomes of children and young people aged 0–18 years with PCR-confirmed SARS-CoV-2 infection who were hospitalised with acute COVID-19 during December 2020 to January 2022.

	Age	Underlying condition	Clinical Presentation	Hospital days	ICU days	Oxygen	Treatment
1.	‹1 year	Prematurity	Respiratory distress, pneumonia	3	3	Y	None
2.	‹1 year	Prematurity, chronic lung disease	Apnoea, pneumonia	8	6	Y	None
3.	‹1 year	Primary immunodeficiency	Chronic diarrhoea, failure to thrive, then pneumonia	8	-	N	None
4.	‹1 year	None	Pneumonia	2	-	N	None
5.	5–11 years	Malignancy	Febrile neutropaenia	29	-	Y	Steroids and antivirals
6.	5–11 years	Malignancy	Gram-negative bacterial sepsis, then pneumonia	13	2	Y	None
7.	12–18 years	Malignancy	Gram-negative bacterial sepsis, then pneumonia	10	-	Y	Steroids and antivirals
8.	12–18 years	Malignancy	Febrile neutropenia and pneumonia	10	2	Y	2 admissions: Steroids and antivirals (1st admission), antivirals (2nd admission)
9.	12–18 years	Chronic heart disease	Pneumonia	17	7	Y	Steroids and antivirals
10.	12–18 years	Malignancy	Pneumonia	10	1	Y	Steroids and intravenous immunoglobulin
11.	12–18 years	None	Pneumonia	6	-	Y	Steroids and antivirals
12.	12–18 years	Malignancy	Febrile neutropenia, pneumonia	5	1	Y	Steroids
13.	12–18 years	Primary immunodeficiency	Prolonged fever	10	-	N	Antivirals
14.	12–18 years	None	Fever and dehydration	1	-	N	None
15.	12–18 years	Chronic liver disease	Pneumonia	4	-	Y	Steroids

ICU, intensive care unit.

In our hospital, more than half the CYP hospitalised with a positive SARS-CoV-2 PCR-test had incidental infection. In a further third, SARS-CoV-2 likely contributed to hospitalisation with clinical presentations that were typical of other respiratory viruses that are currently not circulating in England because of the physical distancing measures imposed during various lockdowns.⁶ This group included mainly high-risk CYP (young infants, immunocompromised) who typically presented with fever and mild respiratory symptoms but were hospitalised to rule serious underlying infection. Of the few CYP hospitalised with COVID-19 pneumonitis, most were adolescents and nearly all had underlying conditions, especially immunosuppression. They all recovered, consistent with current literature reporting favourable outcomes, including for CYP with comorbidities and immunosuppression.^{1 , 7} Vaccinating children against COVID-19 will further reduce the small risk of severe disease,8, 9, 10 but, since current vaccines provide only limited short-term protection against infection or mild disease,^{8 , 9} the virus will likely continue to contribute indirect hospitalisations, just like other respiratory viruses. In conclusion, unlike adults, hospitalisation with a positive SARS-CoV-2 PCR-test is not a useful marker of severe COVID-19 in children. Our findings demonstrate that, not only do CYP have a very low risk of hospitalisation with SARS-CoV-2 infection, but the vast majority of hospitalised CYP (especially healthy CYP) with confirmed SARS-CoV-2 infection do not have severe COVID-19, irrespective of SARS-CoV-2 variant, while the minority with severe COVID-19 recovered without complications. The very low rate of severe COVID-19 during the omicron variant wave is also reassuring.

Declaration of Competing Interest

None.