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Test Shows Big Drop in Pfizer’s Neutralising Antibodies Versus Omicron

Test Shows Big Drop in Pfizer’s Neutralising Antibodies Versus Omicron

A SEM image shows of SARS-CoV-2 isolated from a patient in the US, emerging from the surface of cells (blue/pink) cultured in the lab. Image: NIAID/Flickr, CC BY 2.0

A member of the Network for Genomic Surveillance in South Africa has revealed that laboratory tests done in the nation – its results published last night – showed a 40-fold reduction in neutralising antibodies induced by two doses of the Pfizer vaccine against an infection of the omicron variant of the novel coronavirus.

STAT News described the study as “small” and “preliminary”, and summarised the results thus:

The results support the hypothesis that the Omicron variant is a larger threat to immunity against Covid-19 than other variants, but experts caution that the implications for real-world protection are limited. … [The study’s authors and independent experts also said] previous infection combined with vaccination, or primary vaccination combined with booster doses, can amp up the body’s neutralising power even against a variant as evolved as omicron.

In a 40-minute interview to The Wire, Dr Richard Lessells called the findings “very significant” and that they put the omicron variant “clearly in a different league”. He said this is “not good news” – even as he took pains to point out that the reduction pertained only to neutralising antibodies, and didn’t extend to T cells and B cells.

Neutralising antibodies refers to the immune mechanism that deals with viral particles while they’re still in the blood and before they’ve entered the bloodstream. T cells and B cells kick in once the particles have invaded cells.

Dr Lessells, a senior infectious diseases specialist at the University of KwaZulu Natal in South Africa, also said protection against severe disease is likely to continue even though researchers hadn’t yet tested that aspect. He also said he expected the results to be “broadly consistent across all vaccines”.

He also said the omicron variant could seem to be more transmissible than the delta variant – which itself was the most transmissible variant of concern on its way to becoming the dominant strain in populations around the world. He added that the omicron variant could lead to three-times more reinfections compared to the number caused by the other variants thus far.

Specifically Dr Lessells said the omicron variant could be as transmissible as the delta variant – or even less so – but that its ability to reinfect people who’d had a novel coronavirus infection before makes its ‘susceptible population’ larger than it might have been for the delta variant.

He also said that it’s still too early to speak with any uncertainty about the omicron variant’s ability to cause more or less severe COVID-19. This is partly because the variant’s first patients have been young (typically younger than 30 years). He confirmed reports from the South African Medical Research Council that most patients in hospitals with infections of the omicron variant haven’t required supplemental oxygen or ventilation.

Watch the full interview here.

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