Laboratory research from South Africa has suggested that the SARS-CoV-2 Omicron variant escapes antibody immunity induced by the Pfizer-BioNTech (Comirnaty) vaccine, but that considerable immunity is retained in people who were both vaccinated and previously infected.
The research, led by Professor Alex Sigal from the Africa Health Research Institute (AHRI) in South Africa, has been submitted to medRxiv, a preprint server for health sciences.
The research confirms predictions that a large number of mutations in the spike protein and elsewhere on the Omicron variant would translate into some evasion of the immune response induced by current vaccines.
It also shows that Omicron – despite its many mutations – still requires binding to the angiotensin-converting enzyme 2 (ACE2 ‘receptor’) in order to infect cells, the researchers said.
Sigal’s researchers’ team used plasma, which is a blood product that contains antibodies, from 12 vaccinated people and added either live Omicron or live ancestral (original) SARS-CoV-2 virus. The ability of the antibodies in the plasma to control the two viruses was compared – a so-called ‘neutralization’ test, the researchers said. They found that there is an extensive, 40-fold decrease in the ability of antibodies from the Pfizer-BioNTech vaccine to neutralize the Omicron variant, compared with the ancestral virus.
However, the plasma of those who had both been vaccinated and had a previous infection show relatively high neutralization against Omicron, they added.
“This was better than I expected of Omicron,” said Sigal in a release. “The virus is so changed, there was concern that it uses a different receptor, not ACE2. If that were the case, many of our pharmacological tools to control this virus would become useless. But this is not the case. Instead, previous infection, followed by vaccination – or likely a booster – is probably protective against Omicron, and almost certainly against severe disease. So, Omicron is a tractable problem with the tools that we have already got.”
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