Hong Kong: A team of researchers from Hong Kong University (HKU) has given an explanation on why the Omicron variant of the SARS-CoV-2 virus transmits faster. They reported that the new variant multiplies 70 times faster in the bronchi than the original SARS-CoV-2 and the Delta virus.
According to the authors, these are the first findings on how the Omicron variant (B11529) infects the respiratory tract. Also, they found that Omicron infection in the lung is significantly lower than the original virus, which may be an indicator of lower disease severity.
In the study conducted by Michael Chan Chi-wai and the team, the researchers used lung tissue samples for comparing infection with the recent Omicron variant compared with Delta and the original virus from 2020. The study is under peer review for publication.
They found that Omicron replication was 70 times higher than the other two viruses 24 hours after infection. Also, they found that Omicron replication was less efficient in deeper lung tissue—more than 10 times lower than the original virus giving a potential clue on its lower severity.
In an HKU press release, Michael Chan emphasized that virus replication is not the only factor driving disease severity, host immune response can also play a role, such as the immune system dysregulation that leads to cytokine storm.
By infecting more people, a very infectious virus may cause more severe disease and death, even if the virus itself is less pathogenic, he said.
He also said by infecting more people, a very infectious virus may cause more severe disease and death, even if the virus itself is less pathogenic. Considering earlier findings that Omicron can partially escape immunity from vaccination and past infection, the overall threat will likely be significant, Chan Chi-wai said.
In other research development, a separate team from HKU found that people who received two doses of either the Pfizer-BioNTech or China's Coronavac vaccine don't produce enough antibodies against Omicron.
The researchers used blood from people who had received both doses of one of the two vaccines to explore antibody response to Omicron. Each group consisted of 25 people. In addition, they also explored how well the serum antibodies neutralized the Alpha, (B117), Beta (B1351), and Delta variants.
They found that only 5 of the Pfizer recipients produced neutralizing antibodies against Omicron. This translates to a 36- to 40-fold reduction compared with the original SARS-CoV-2 virus. However, none of the recipients of the Coronavac vaccine had enough antibodies to neutralize Omicron.
The findings highlight a breakthrough infection risk in vaccinated people and those who had previous infections. Also, the results support the use of third vaccine doses. Although it is still not clear if the third dose of Coronavac will shore up the antibody response.