Breakthrough infections in vaccinated individuals tend to be mild, but will not always be so, especially in older people, Jeffrey Dorfman said.
A leading virologist in South Africa, where the Omicron variant has emerged, expects current vaccines will continue to protect those vaccinated against severe disease and death from Covid-19. Jeffrey Dorfman, Associate Professor in Medical Virology at Stellenbosch University, discussed the variant and its implications:
On optimism about vaccines
“This is because the protection [from vaccines] seems to be mediated by T cells, which can recognise any part of the virus, as opposed to neutralising antibody, which is focused upon the receptor binding domain, a part of the spike protein. We do not know a lot about the variant yet. There is no `direct’ evidence of immune escape — but that should come over the next few weeks,” said Dorfman, who has been researching HIV and other infectious diseases.
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Too few people have been infected with Omicron and identified as such, he noted. “However, our previous experience suggests that the vaccines will still prevent hospitalisation and death from Covid — but we don’t know exactly how well. Also, case numbers will go up faster and higher if previous infection with other variants does not prevent infection with this new variant very well — and having more virus around is more dangerous. We just don’t know yet,” Dorfman said.
On breakthrough infections
Breakthrough infections in vaccinated individuals tend to be mild, but will not always be so, especially in older people, he said. “We also see what seems like a younger average age of people getting severely ill from Covid. A lot of that is a result of targeting vaccination to older people… As variants get more contagious, more people get infected, and the ones who get sick are the ones who were not infected recently and not vaccinated (generally, not 100%). We also get more children getting sick as they return to school… I am not aware of any evidence to suggest that what we see is more than these effects,” he said
On mutations in combination
Dorfman referred to the range of mutations in Omicron, many (but not all) of which have been seen before — and never all together in the same variant. “We are concerned that protection, particularly protection from infection may be reduced. Also, it seems to be able to spread quickly, but the evidence for that is currently thin — there are about 70 or 80 cases detected in Gauteng province here in South Africa as of Wednesday last week,” he said.
On travel restrictions
Asked travel advisories issued by countries, he said: “Restrictions will curtail spread, perhaps for a short while. But it is probably already too late.”
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“Estimates based upon the sequences we now hold suggest that Omicron came to be sometime between mid-September to mid-October, enough time to spread where there is little surveillance. There is also a worrying case of a woman who returned home to Belgium from Egypt with the variant. The other reports that I have seen are all linked to southern Africa… If it is common enough in Egypt that a short-term traveller got it, then we should be worried,” he said.
He said there is limited benefit to the delay that travel restrictions will give. “In the case of Delta, some countries were starting to vaccinate, and keeping Delta out for a couple of months while vaccination rates went up might be counted as an important benefit. Now, few countries are in that position, and the public health benefit to a delay is more limited,” he said.
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