Study: Initial COVID vaccination or prior infection offer ‘virtually no protection against Omicron’

VIENNA, Austria — New research from the Medical University of Vienna finds that receiving a third booster shot achieves partial antibody protection against the Omicron variant. Scientists report both initial dual vaccination and recovering from infection with an earlier COVID-19 strain offer virtually no protection against Omicron. Currently, Omicron is the most contagious version of SARS-CoV-2 by a wide margin.

Study authors examined COVID-19 antibodies among a collection of either vaccinated or recovered Austrians. In addition, they looked for signs of specific antibodies associated with various strains of SARS-CoV-2, from the original version first detected in Wuhan, China, to Delta, as well as Omicron.

To accomplish such a complex task, researchers developed a test capable of identifying whether the Omicron variant of SARS-CoV-2 specifically can bind to the receptor on human cells via its receptor binding domain (RBD). Test results confirmed that while recovering from an earlier case of COVID-19 and double initial vaccination provides robust protection against Delta, those same antibodies do very little to block receptor binding against Omicron. The team tested all possible combinations of COVID-19 vaccines currently available in Austria.

Third vaccine dose shows strong protection from Omicron

On a more positive note, Austrians who had received a third vaccine dose displayed stronger resilience to Omicron.

“The third vaccination developed protective antibodies in many individuals,” Rudolf Valenta of the Medical University of Vienna, Institute of Pathophysiology and Allergy Research explains in a statement, “however, there is also a significant proportion (20 percent) in whom no protection was established.”

The RBD that the coronavirus uses to infect and enter new human cells via the ACE2 receptor had primarily stayed the same until Omicron. Earlier variants’ RBDs were all unique. However, their general similarities meant prior infection and/or initial vaccination continued to provide a certain degree of protection. Because of its radically different RBD, people have a more challenging time protecting themselves against Omicron.

What’s the best solution? In Valenta’s opinion, researchers can develop a “broadly effective combination vaccine” that offers comprehensive protection against both Omicron and all other previous versions of SARS-CoV-2.

“Until we have such a vaccine, only repeated vaccinations with the existing vaccines will provide some protection. The protective effect achieved by vaccination can be evaluated with special tests that can be rapidly adapted to new virus variants,” Valenta concludes.

The study is available to read in the journal Allergy.