Booster shots with mRNA vaccines such as those made by Pfizer failed to block Omicron in some of the first documented breakthrough COVID-19 cases caused by the highly contagious variant, according to a new South African study.
German visitors to Cape Town experienced symptomatic COVID-19 between late November and early December despite already being boosted with mRNA vaccines, researchers said in findings published on Tuesday (Jan. 18) in The Lancet.
The study clearly demonstrates Omicron’s ability to evade immunity generated by COVID-19 mRNA vaccines.
“The presence of this group from Germany presented a unique opportunity to study Omicron breakthrough infections in individuals with mRNA vaccine boosters,” the researchers said.
Meanwhile, preliminary data from an Israeli trial involving 154 health workers released on Monday (Jan. 17) showed that even a fourth dose of Pfizer’s COVID-19 mRNA vaccine didn’t stop Omicron.
Better vaccines will be needed to stop symptomatic infections with Omicron, they concluded.
Israel’s Sheba Medical Center has given second COVID-19 booster shots in a trial among its staff and studied the effect of the Pfizer booster in 154 people after two weeks and the Moderna booster in 120 people after one week, said Gili Regev-Yochay, director of the Infectious Diseases Unit.
These were compared to a control group that did not receive the fourth shot. Those in the Moderna group had previously received three shots of Pfizer’s vaccine, the hospital said. The fourth dose led to a increase in the number of antibodies “a little bit higher than what we had after the third dose,” said Regev-Yochay.
“Yet, this is probably not enough for the Omicron,” she told reporters. “We know by now that the level of antibodies needed to protect and not to got infected from Omicron is probably too high for the vaccine, even if it’s a good vaccine.”
The findings, which the hospital said were the first of its kind in the world, were preliminary and not yet published.