A third dose of both the AstraZeneca and Pfizer-BioNTech COVID-19 vaccines significantly increased the immune response to the omicron variant, according to a new study by University of Oxford researchers.

The laboratory study, which hasn’t been peer reviewed yet, compared antibody levels in blood samples from people who received two doses of vaccine with samples from those who had received a third dose.

While two doses provided much less protection against omicron than earlier variants, levels of neutralizing antibodies rose sharply after a third dose, the study found.

Also read: Boosters key to fight omicron, lot still to learn

“In summary, neutralization titres against omicron are boosted following a third vaccine dose, meaning that the campaign to deploy booster vaccines should add considerable protection against omicron infection,” the researchers wrote.

The study also found that unvaccinated people who had recovered from COVID-19 probably have “little protection from reinfection with omicron,” though they may have some protection against serious illness.

Also read: Moderna: Initial booster data shows good results on omicron