WASHINGTON (The Hill) — An Oxford University study published on Monday found that two-dose COVID-19 vaccines generate a lower antibody response against the omicron strain, suggesting that the variant could lead to more infections among the fully vaccinated and previously infected.

The research, which has not yet been peer-reviewed, documented a “substantial fall” in the number of neutralizing antibodies, among participants who received two doses of the AstraZeneca or Pfizer-BioNTech vaccines.

The results do not provide evidence that the omicron strain causes more severe disease, hospitalizations or deaths in vaccinated individuals. But it does indicate that the variant could lead to more cases among those vaccinated with two doses.

The study adds to a growing body of evidence supporting the push for booster doses that have been shown in other research to boost antibody levels against the omicron strain. “Increasing vaccine uptake among unvaccinated, and encouraging third doses, remain priority to reduce transmission levels and potential for severe disease,” an Oxford University release said.

Researchers examined how an omicron virus isolate affected the immune response in the blood samples of previously vaccinated participants in a study cohort. Lead author Gavin Screaton who heads the university’s medical sciences division said the study should “press home the message that those who are offered booster vaccination should take it.”

“Whilst there is no evidence for increased risk of severe disease, or death, from the virus amongst vaccinated populations, we must remain cautious, as greater case numbers will still place a considerable burden on healthcare systems,” Screaton said in a release.

The preprint study comes as the U.K. is sounding alarm bells over the omicron variant, with Prime Minister Boris Johnson advocating for boosters and warning of an upcoming “tidal wave of omicron.” 

The U.K. raised its COVID-19 alert level to its second-highest level as omicron cases have doubled in the country “every two to three days,” Johnson said Sunday. The U.K. Health Security Agency has predicted the strain will be dominant by mid-December.

More than half of states, as well as D.C., have reported cases of the omicron variant.