Omicron does reinfect after natural infection

Reinfections are probable, not good news actually How likely somebody who has already had Covid to catch Omicron? (catching it twice or more) Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa What is…

Omicron does reinfect after natural infection

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Reinfections are probable, not good news actually

How likely somebody who has already had Covid to catch Omicron?

(catching it twice or more)

Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa

What is already known on this topic

https://www.medrxiv.org/content/10.1101/2021.11.11.21266068v2.full.pdf

Prior infection with SARS-CoV-2 is estimated to provide 84% reduction in infection risk

What this study adds

We find no evidence of increased reinfection risk associated with circulation of Beta or Delta variants,

compared to the ancestral strain in routine epidemiological data from South Africa.

In contrast, we find clear, population-level evidence to suggest substantial immune evasion by the Omicron variant.

Omicron selection advantage is at least partially driven by an increased ability to infect previously infected individuals.

Omicron variant increases reinfection risk – Yes

Omicron variant of SARS-CoV-2 demonstrates substantial population-level evidence for evasion of immunity from prior infection.

Retrospective analysis of routine epidemiological surveillance data

4th March 2020 to 27th November 2021

South Africa’s National Notifiable Medical Conditions Surveillance System

N = 2,796,982

Laboratory-confirmed SARS-CoV-2

Results

35,670 suspected reinfections were identified

among 2,796,982 individuals with laboratory-confirmed SARS-CoV-2,

who had a positive test result at least 90 days prior to 27th November 2021

35,670 individuals with at least two infections

332 individuals with third infections

1 individual with four infection

The relative hazard ratio for wave 2 versus wave 1 was 0.75

The relative hazard ratio for wave 3 versus wave 1 was 0.71

Relative hazard ratio for the period from 01 November 2021 to 27 November 2021

The relative hazard ratio for wave 4 versus wave 1 was 2.39

In the time of beta and delta

Increases in primary infections

No corresponding increase in reinfection hazard

In the time of omicron

Omicron variant, decrease in the hazard for primary infection

Increase in reinfection hazard coefficient

Conclusion

Population-level evidence suggests that the Omicron variant is associated with substantial ability to evade immunity from prior infection.

In contrast, there is no population-wide epidemiological evidence of immune escape associated with the Beta or Delta variants.

This finding has important implications for public health planning,

particularly in countries like South Africa with high rates of immunity from prior infection.

Urgent questions remain regarding whether Omicron is also able to evade vaccine-induced immunity,

and the potential implications on protection against severe disease and death.

Prof Paul Hunter

The implications of this paper are that Omicron will be able to overcome natural and probably vaccine-induced immunity to a significant degree.

But, the degree is still unclear – though it is doubtful that this will represent complete escape.

Prof Francois Balloux, University College London

The higher estimated re-infection ability of the Omicron variant to cause re-infection is not overly surprising

and could be largely anticipated based on the large number of mutations in the spike protein carried by the omicron variant,

which increase the Omicron variant’s ability to bypass host immunity

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