COVID-19 vaccines from US drugmaker Johnson & Johnson and China's Sinopharm as well as Russia's Sputnik V shot had no neutralizing activity against the Omicron variant, according to a study which has not yet been peer reviewed.

The Omicron variant has raised concerns regarding its ability to evade protection provided by widely-used vaccines, with drugmakers tailoring their shots to target the variant while testing the effectiveness of their existing shots.

Vaccines from Moderna, AstraZeneca and Pfizer and partner BioNTech retained activity against Omicron, but the antibody response was greatly reduced when compared with the original virus strain first detected in China, the study found.

WHO warns Covid variant Omicron risk ‘very high’

The study, conducted by Humabs Biomed SA, a unit of Vir Biotechnology and the University of Washington, among others, also found the decrease was less pronounced for vaccinated individuals who were previously infected.

The study also found that while the effectiveness of GlaxoSmithKline and Vir Biotech's COVID-19 drug sotrovimab reduced three-fold against Omicron compared to the original strain, monoclonal antibody treatments by Regeneron and Eli Lilly completely lost their neutralizing activity against the variant.

The finding is consistent with recent laboratory tests demonstrating the two treatments lose most of their effectiveness when exposed to the Omicron variant.

WHO sees unprecedented Omicron spread, 'probably' in most countries

In a real-world study published this week, it was seen that Pfizer-BioNTech's COVID-19 vaccine has been less effective in South Africa at keeping people infected with the virus out of hospital since the Omicron variant emerged last month.