Omicron and older people. New data on severity and hospitalisations from South Africa.
By Peter Lloyd-Sherlock
On 21 December 2021, South Africa’s National Institute for Infectious Diseases published new data on Omicron [link]. The data are able to differentiate between cases that are almost certainly Omicron variant (S-gene target failure) and those related to other variants (essentially Delta).
With specific reference to Omicron cases identified in October and November 2021, 2.5% (261 out of 10,547) were admitted to hospital, compared to 12.8% (121 of 948) of individuals with non-SGTF infection.
Risk of hospital admission was significantly higher for people aged under 5 and 60+. For example, the risk for admission for 60+ was about 3 times that for people aged 19-24 (odd ratio 3.1, 95% CI 1.9-5.0).
Among those hospitalised (and controlling for other factors that can cause serious disease) the risk of severe symptoms was significantly higher for people aged 60+. For example, the risk for severe symptoms for 60+ was more than 10 times that for people aged 19-24 (odd ratio 11.5, 95% CI 2.8-47.0), compared to individuals aged 19-24 years.
Key take-homes for other countries.
There is still tremendous uncertainty about the likely effects of Omicron on severe illness, hospitalisation and mortality. These South Africa data offer some insights, but they may not predict longer-run outcomes or what happens in other countries.
Despite this, the data are useful to guide ongoing preparations for this new wave of the pandemic. They demonstrate that risk of hospitalisation and, especially, risk of severe symptoms are strongly linked to old age. There are no obvious reasons why this will not be the case in other countries, and (until new data emerge) this should be factored into emergency planning.
The South African data refer to the period ending 30 November 2021. Since then, it is likely that some severe cases of Omicron will have led to deaths and that these will be concentrated among the oldest.
“Early assessment of the clinical severity of the SARS-CoV-2 Omicron variant in South Africa”. Nicole Wolter, Waasila Jassat, Sibongile Walaza, Richard Welch, Harry Moultrie, Michelle Groome, Daniel Gyamfi Amoako, Josie Everatt, Jinal N. Bhiman, Cathrine Scheepers, Naume Tebeila, Nicola Chiwandire, Mignon du Plessis, Nevashan Govender, Arshad Ismail, Allison Glass, Koleka Mlisana, Wendy Stevens, Florette K. Treurnicht, Zinhle Makatini, Nei-yuan Hsiao, Raveen Parboosing, Jeannette Wadula, Hannah Hussey, Mary-Ann Davies, Andrew Boulle, Anne von Gottberg, Cheryl Cohen. medRxiv 2021.12.21.21268116; doi: https://doi.org/10.1101/2021.12.21.21268116