U.S. study suggests vaccines may be ineffective against Omicron without booster

All three U.S.-authorized COVID-19 vaccines appear to be significantly less protective against the newly-detected Omicron variant of the coronavirus in laboratory testing, but a booster dose likely restores most of the protection, according to a study released on Tuesday.

The study from researchers at Massachusetts General Hospital (MGH), Harvard and MIT that has not yet been peer reviewed tested blood from people who received the Moderna (MRNA.O), Johnson & Johnson (JNJ.N) and Pfizer (PFE.N)/BioNTech vaccines against a pseudovirus engineered to resemble the Omicron variant.

The researchers found "low to absent" antibody neutralization of the variant from the regular regimens of all three vaccines - two shots of the Moderna or Pfizer/BioNTech vaccines or one of J&J's single-dose vaccine.

But the blood from recent recipients of an additional booster dose exhibited potent neutralization of the variant, the study found.

The scientists also suggested that Omicron is more infectious than previous variants of concern, including about twice as transmissible as the currently dominant Delta variant, which may soon be overtaken by Omicron.