Covid vaccines, previous infection offer stronger than basic' protection against Omicron: Study

People previously infected with COVID-19 and those vaccinated will have some "stronger than basic" protection against Omicron, according to one of the earliest peer-reviewed studies looking into the recently identified variant of coronavirus.

However, the study conducted in a lab suggests that Omicron "exceeds" all other variants in its potential capability to evade the protection gained from previous COVID-19 infection or vaccination.

The findings, published in the journal Emerging Microbes & Infection, also suggest that although a third-dose of vaccines can significantly boost immunity", the protection from Omicron "may be compromised".

The researchers from the National Institutes for Food and Drug Control in China, however, noted that more research is needed to better understand the association.

The results support recent findings in South Africa which highlight that for Omicron it was easy to evade immunity, they noted.

"We found the large number of mutations of the Omicron variant did cause significant changes of neutralisation sensitivity against people who had already had COVID," said study lead author Youchun Wang from the National Institutes for Food and Drug Control.

"However, the average ED50 (protection level) against Omicron is still higher than the baseline, which indicated there is still some protection effect that can be observed," Wang said.

Wang cautioned that because the antibody protection -- in the form of previous infection or vaccination -- decreases gradually over a period of six months, Omicron "may be able to escape immunity even better".

The researchers looked at 28 serum samples from patients recovering from the original strain of SARS-CoV-2.

They tested these against in-vitro Omicron samples, as well as four other strains marked 'of concern' by the World Health Organization such as Delta, and two variants marked as of interest'.

"This study verifies the enhanced immune escape of Omicron variant, which sounds the alarm to the world and has important implications for the public health planning and the development of matching strategies," Wang said.

The researchers noted that more research carried out not just in-vitro but in real-world studies is urgently needed to better understand Omicron.

It will be of utmost importance to know whether the variant can escape from the vaccine elicited immunity to cause more severe disease and death, they said.

"It needs to be re-evaluated whether the antibodies can still be effective against the Omicron variant," the authors of the study noted.

"The exact impact to human protection may be influenced by more factors such as the infectivity of Omicron variant relative to other variants to human populations and the viral fitness of Omicron once the humans are infected," they added.

More population studies including the level of immune protection and symptoms among people infected with Omicron are needed to fully establish the global impact of Omicron to the control of COVID-19 pandemic, the researchers said.

The major caveat of this study is that it is in-vitro in nature and that it used pseudotyped or manufactured viruses, the researchers said.

However, the current vaccine literature "has established that the in-vitro neutralisation assays are good predictors of vaccine protection efficacy and real-world vaccine effectiveness," they said.

Therefore, the authors said their data "may well predict the potential reduction of vaccine protection against the new Omicron variant".