A new study from South Africa may indicate that the Omicron variant can break through booster shot immunity.

The study, which was obtained by Reuters, involved seven German visitors to Cape Town, South Africa, who were aged 25 to 39 and were infected with the Omicron variant from late November to early December.

The patients – six of whom were vaccinated with the Pfizer-BioNTech COVID vaccine and five of whom had received Pfizer booster shots with one receiving a Moderna booster dose - had mild to moderate symptoms and none required hospitalization, Reuters reported.

One study participant had received two doses of the AstraZeneca vaccine and a booster dose of the Pfizer shot, according to the news outlet.

None had prior COVID infections but did become infected with the Omicron variant one to two months after inoculation of their booster shots, the study indicated.

Wolfgang Preiser, a virologist at Stellenbosch University and one of the study’s co-authors, told Reuters the study showed that infection from the Omicron variant was possible and caused symptomatic disease even after boosted immunization.

The study, however small, is under peer review, with Preiser maintaining that vaccinations are still important to combating the virus.

“It still protects against severe disease and death: we are quite sure about that,” he told Reuters, adding, “the picture emerging is that this virus is very capable of undermining the immune response … (so) it’s clear that we will need an updated vaccine.”

South African doctor Angelique Coetzee, who sounded the alarm about Omicron in late November after seeing symptoms in her patients, described the symptoms of the variant to the BBC as “extremely mild.”

She told the news outlet, “What we are seeing clinically in South Africa — and remember I’m at the epicenter of this where I’m practicing — is extremely mild. For us [these are] mild cases.”

Her patients reported symptoms of a scratchy throat, headache, fatigue, and body aches and pains. They did not have a cough or loss of taste or smell.

The Omicron variant is proving to have a high degree of transmissibility, with cases of the variant being reported in at least 37 U.S. states.

Cases in Europe are doubling every two to three days, with the U.K. being one of the hardest-hit countries for the new COVID strain. The U.K. saw the first death from Omicron on Monday.

A health worker prepares the Pfizer-BioNtech Covid-19 vaccine in the city of Joinville, Santa Catarina, Brazil
A health worker prepares the Pfizer-BioNtech Covid-19 vaccine in the city of Joinville, Santa Catarina, Brazil AFP / Carlos JUNIOR