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NICD analysis finds Omicron subvariant increases risk of reinfection

The National Institute for Communicable Diseases (NICD) says your chance of contracting COVID-19 again is much higher if you had the Omicron strain, rather the Delta or Beta variants, even though total infections countrywide are decreasing.

The latest analysis by the NICD of reinfection trends since the Omicron subvariant emerged showed a marked increase in the reinfection risk that was not evident with the Delta and Beta variants.

The study was authored by leading COVID experts, including Professor Juliet Pulliam, director of the South African Centre for Epidemiological Modelling and Analysis (Sacema); Professor Jonathan Dushoff, an infectious disease expert from McMaster University in Canada; Dr Michelle Groome, Professor Anne von Gottberg, Professor Cheryl Cohen and Nevashan Govender, all from the NICD; Professor Koleka Mlisana from the National Health Laboratory Service; Professor Harry Moultrie from the University of the Witwatersrand; Siobhan Johnstone from the NICD; and Cari van Schalkwyk from Sacema.

Additionally, reports Daily Maverick, the analysis also found that the two subvariants dominant in South Africa, BA.4 and BA.5, also caused a gradual increase in reinfections but not higher than the “original” Omicron variant (BA.1).

Scientists started tracking reinfection risk in January 2022, a month after Omicron was first identified in Tshwane and designated as a variant of concern by the World Health Organisation.

The authors said they noted that a similar reinfection risk was not seen when Beta and Delta variants dominated infections in SA.

In their latest report, they analysed data up to 31 August and found the reinfection risk had remained constant since the first outbreak of the Omicron subvariant and that the risk had not changed as other subvariants emerged.

Omicron was first identified late in 2021. The analysed data showed that second and third infections spiked between December 2021 and January 2022.

Heightened risk

This research follows a Discovery Health study that investigated reinfection risks before Omicron came on the scene, using data from the first three waves before vaccines became available.

The resulting analysis (of medical scheme member data) showed an 80% decrease in relative reinfection risk and that the risk decreased with each successive wave.

Discovery Health’s data showed a 20% relative possible reinfection risk within 90 days after the recovery from the first infection (with the “original” COVID-19 virus).

Further findings of this study included:
• 36.3% of patients were infected in the first and second waves; and
• 13.7% of people who first contracted COVID-19 during the second wave contracted the disease for a second time during South Africa’s third wave of infection.

Current SARS-CoV-2 infection numbers, released by the NICD on 8 September, show that the number of confirmed infections is still dropping, as is the number of hospital admissions as a result of complications caused by the virus.

In the week up to 8 September, 1 475 cases of confirmed infections were reported: 5% lower than the previous week. There has been an increase in test positivity for the older age groups (older than 75), said the NICD, and a 40% decrease in the number of new admissions in the past week compared with the week before.



Daily Maverick article – Covid reinfection – Omicron subvariant increases your risk, study finds (Open access)


See more from MedicalBrief archives:


Discovery Health’s large real-world analysis of Omicron


Boosters up to 68% effective against hospitalisation following Omicron reinfection – CDC study


Increased risk of SARS-CoV-2 reinfection associated with Omicron — South African study


‘Most transmissable’ Omicron variant re-infects within weeks


Omicron sub-variant BA.2 warning for US as European cases surge



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