A new Pediatric COVID-19 study showed that many children upon being infected with the BA.2 variant or subvariants, developed disease severity requiring intensive care and supplemental oxygen and a few died from the BA.2 infections.
The study findings showed that the intrinsic severity of Omicron BA.2 is not mild as evident by the fatality and severe complications of the uninfected and unvaccinated children.
The study findings were published on a preprint server by Lancet.
During the pre-vaccination era of Coronavirus disease 2019 (COVID-19), 469982 out of 12 million children and young people <18 years old (CYP) in the United Kingdom (UK) had been reported to be infected with SARS-CoV-2 in the first year of the pandemic, mostly by the wild type and Alpha variant, and the infection fatality rate (IFR) was 5 per 100000 (0.005%)1.
Since then, other variants, such as Beta, Gamma and Delta also swept across the globe, leading to over 6 million total deaths to date, of which 0.4% were estimated to be in children2-5. For many of those who survived, their convalescent sera demonstrated antibody protection across variants, which, in combination with vaccination, can induce hybrid immunity against COVID-196,7.
By the time Omicron emerged in November 2021, symptoms appeared to be milder than previous variants, and paediatric deaths were rare, but these were observed in populations in which a majority was already protected from a high degree of immunity from past infection, vaccination or both8. Therefore, the intrinsic severity of Omicron in children remains unknown 9,10.
The setting in Hong Kong (HK) can provide the prototypical platform for understanding the intrinsic severity of Omicron in children 0-11 years old. Since the onset of the pandemic, the HK Government implemented stringent social distancing policies, including universal masking, contact tracing, intermittent business closures and territory-wide school suspensions.
From January 2020 to March 2022, school attendance was reduced from around 400 days to just 300 days, and even during reopening, students were allowed to attend only half-day of face-to-face lessons11-15.
These measures were associated with one of the lowest recorded numbers of COVID- 19 for the past 2 years in HK relative to other geographical regions16. Sero-epidemiological studies showed an infection rate of approximately 1% of the population of HK as of 31 October 2021 (Peiris-personal communication).
Furthermore, COVID-19 vaccines were only approved for HK children aged 5-11 years old in mid-January 2022, so these children were both uninfected and unvaccinated at the start of the Omicron wave in HK17.
The highly contagious Omicron, predominantly of the BA.2 sublineage in HK, led to exponential increases of SARS-CoV-2 infections of more than 900000 new cases since the start of the fifth wave of COVID-19 between 31 December 2021 to 15 March 2022 as compared to the mere 14197 cases over a 2-year period throughout the first 4 waves 16,18.
Indeed, although children have generally experienced more favourable outcomes than older adults in HK during the first 4 waves as similarly observed internationally, recent studies have described disproportionately higher hospitalisation rates in children after the emergence of Omicron19,20.
Furthermore, these cases appear to have a greater predilection for more severe complications affecting the neurological and respiratory systems. In an observational study of the first Omicron wave, likely predominated by the BA.1 sublineage, the most frequent clinical diagnoses linked to paediatric hospitalisation was seizure8.
Other studies suggested that laryngotracheobronchitis, or croup, is more prevalent, severe and prolonged with Omicron than other variants21-23.
Deaths in children infected with Omicron have occurred but were all related to complex underlying co- pathologies 8. Such emerging data are reshaping the notion that Omicron may not be as mild as initially speculated.
To understand the intrinsic severity of Omicron, this population-based study aimed to describe Omicron BA.2-dominant fifth wave’s severe outcomes in hospitalised children aged 0-11 years, who basically lack immune exposure to past COVID-19 infections or vaccination.
Additionally, we compared the neurological and respiratory complications in hospitalised children aged 0-11 years during this fifth wave of COVID-19 to previous waves and to other common respiratory viruses—influenza and parainfluenza virus infections—before the COVID-19 pandemic.