A study from South Africa of seven participants found that mRNA COVID-19 boosters failed to prevent infections from the Omicron variant.
Results, published in The Lancet, were based on a group of seven German visitors to the country who experienced Omicron breakthrough infections. Five were women and two were men. All were between the ages of 25 and 39 years old.
None of the seven said they previously were diagnosed with COVID.
Five received three doses of the Pfizer and BioNTech vaccine. One had the Moderna jab and then the Pfizer shot. The final subject had the AstraZeneca vaccine before switching to the Pfizer vaccine.
The researchers said the seven people experienced mild or moderate disease.
"The mild to moderate course of illness suggests that full vaccination followed by a booster dose still provides good protection against severe disease caused by omicron," they wrote, adding that the findings support the need for vaccines that protect against symptomatic Omicron infection.
Yesterday, an Israeli study found that a fourth vaccine dose was less effective again Omicron than other variants.