The research, led by Rudolf Valenta of the Medical University of Vienna, found that only people who had received the third dose of a COVID-19 vaccine can form antibodies that could partially block Omicron, although noting that the protection is far from optimal.
“The third vaccination developed protective antibodies in many individuals,” Valenta said, adding that “there is also a significant proportion (20 percent) in whom no protection was established.”
According to results of the study recently published in the journal Allergy, researchers with the Medical University of Vienna examined an Austrian subpopulation of people who had been vaccinated or recovered from the CCP (Chinese Communist Party) virus. Scientists examined individuals’ antibody status and protection against the Wuhan, Delta, and Omicron variants, strains that are currently prevalent in the European country.
The study involved people who received all types of COVID-19 vaccines and vaccine combinations currently licensed in Austria.
Regarding the Omicron variant, researchers developed a test for the previous variants that investigates whether the COVID-19 strain can bind to the receptor on human cells via its receptor-binding domain (RBD).
“The results showed that both COVID-19 convalescent individuals and individuals who had been vaccinated twice had developed antibody protection against Delta. However, the antibodies were not able to block receptor binding against Omicron,” the researchers found.
An RBD is a key part used by a virus, including the CCP virus, to enter the “spike protein” domain that allows viruses to dock to the human body, gain entry into cells, and lead to infection.
The RBD differed only slightly in all CCP virus variants previously known, researchers said, adding that the COVID-19 vaccines that are currently available could provide protection against infections caused by these previous strains.
“Omicron is the first variant that differs greatly from the previous variants in RBD, consequently, infections with the previous variants and currently available vaccines provide little or no protection against Omicron,” the study found.
The researchers noted that the best protection would be to develop a broadly effective combination vaccine that could protect against both the previous CCP virus variants and Omicron.
“Until we have such a vaccine, only repeated vaccinations with the existing vaccines will provide some protection,” Valenta said. “The protective effect achieved by vaccination can be evaluated with special tests that can be rapidly adapted to new virus variants.”
Omicron became dominant in the United States in December 2021 and other studies have already suggested it can evade protection from COVID-19 vaccines and prior infection better than Delta. Most previous studies have also found that natural immunity remains superior to vaccination, including while Delta was dominant.
In a recent study, antibody protection against the CCP virus among recovered individuals was detected at 20 months post-infection, adding to the body of evidence that such protection, known as natural immunity, is long-lasting.