High levels of previous exposure to three previous waves of coronavirus infection in South Africa may explain the relatively low levels of hospitalisation and severe disease in the current outbreak of the Omicron variant, rather than the variant itself being less virulent.
The suggestion was made by the vaccine expert Shabir Madhi of the University of the Witwatersrand, who has led vaccine trials in the country. He warned that South Africa’s experience of Omicron might not be a reliable indicator for how the Omicron outbreak unfolds in other countries.
The same message was echoed by the WHO, and Tedros Adhanom Ghebreyesus said it was “Wrong for people to consider Omicron as mild”.
Other senior WHO officials, warning that the peak of Omicron could be weeks away as it spread rapidly, added that current evidence suggested vaccines were not failing to protect against Omicron altogether, and did offer some degree of protection.
While Madhi said emerging evidence pointed to the fact that Omicron was both more infectious and more able to evade antibody protection, he suggested other mechanisms at work in acquired immunity through infection could explain the lower levels of hospitalisations and severe illness.
While the UK has a seropositivity rate above 90%, South Africa’s experience may be very different to the UK’s in terms of the Omicron, with the UK having an older population and different vulnerabilities to disease.
Addressing the issue of whether Omicron is “milder” than other previous variants, Madhi said the high levels of previous exposure meant that experts were “simply unable to make a meaningful head-to-head comparison of virulence with Omicron in comparison with the other variants.
“[That is] imply because of the underpinning of immunity that currently exists which is different to what existed in the past, and that immunity is going to bring about some change in the clinical course of the infection, including the likelihood of infection progressing to severe disease.”
“What is quite fascinating is that taking the rate of infection per 100,000 and comparing that to the hospitalisation rate as well as the death rate, the hospitalisation rate is much more muted compared with what was the equivalent case rate in the first three waves that transpired.
“So it tells us something is at play when the high force of infections with Omicron is not materialising in terms of severe disease and deaths in large numbers.”
Citing evidence of Omicron’s ability to evade antibody protection he suggested data was “congregating” that immunity from T cells might be driving protection against more severe disease.
PS: It seems that the jury is still out there on the decision that whether it's Omicron being mild or whether our immune system gives a better fight.
With the Pfizer vaccine - when it came to avoiding infection altogether, the study by South Africa showed that protection against catching COVID-19 had slumped to 33% from 80% previously.
Between Nov. 15 and Dec. 7, people who had received two doses of the shot had a 70% chance of avoiding hospitalisation, down from 93% during the previous wave of Delta infections, the study showed.
The suggestion was made by the vaccine expert Shabir Madhi of the University of the Witwatersrand, who has led vaccine trials in the country. He warned that South Africa’s experience of Omicron might not be a reliable indicator for how the Omicron outbreak unfolds in other countries.
The same message was echoed by the WHO, and Tedros Adhanom Ghebreyesus said it was “Wrong for people to consider Omicron as mild”.
Other senior WHO officials, warning that the peak of Omicron could be weeks away as it spread rapidly, added that current evidence suggested vaccines were not failing to protect against Omicron altogether, and did offer some degree of protection.
While Madhi said emerging evidence pointed to the fact that Omicron was both more infectious and more able to evade antibody protection, he suggested other mechanisms at work in acquired immunity through infection could explain the lower levels of hospitalisations and severe illness.
While the UK has a seropositivity rate above 90%, South Africa’s experience may be very different to the UK’s in terms of the Omicron, with the UK having an older population and different vulnerabilities to disease.
Addressing the issue of whether Omicron is “milder” than other previous variants, Madhi said the high levels of previous exposure meant that experts were “simply unable to make a meaningful head-to-head comparison of virulence with Omicron in comparison with the other variants.
“[That is] imply because of the underpinning of immunity that currently exists which is different to what existed in the past, and that immunity is going to bring about some change in the clinical course of the infection, including the likelihood of infection progressing to severe disease.”
“What is quite fascinating is that taking the rate of infection per 100,000 and comparing that to the hospitalisation rate as well as the death rate, the hospitalisation rate is much more muted compared with what was the equivalent case rate in the first three waves that transpired.
“So it tells us something is at play when the high force of infections with Omicron is not materialising in terms of severe disease and deaths in large numbers.”
Citing evidence of Omicron’s ability to evade antibody protection he suggested data was “congregating” that immunity from T cells might be driving protection against more severe disease.
PS: It seems that the jury is still out there on the decision that whether it's Omicron being mild or whether our immune system gives a better fight.
With the Pfizer vaccine - when it came to avoiding infection altogether, the study by South Africa showed that protection against catching COVID-19 had slumped to 33% from 80% previously.
Between Nov. 15 and Dec. 7, people who had received two doses of the shot had a 70% chance of avoiding hospitalisation, down from 93% during the previous wave of Delta infections, the study showed.
