The Omicron Variant Partly Evades Vaccine Antibodies, According To A South African Study

“The data suggests this is a more transmissible virus with significant degrees of immune escape, that is going to render the vaccines less effective,” said one expert.

South African researchers on Tuesday reported the Omicron coronavirus variant appears to dodge vaccines, but only partially. The results, from a small laboratory study, suggest people who have recovered from COVID-19 and been vaccinated will retain strong protection, but those who have only received the two-dose vaccine regimen could be significantly more vulnerable to infection. The study did not examine the effects of boosters but suggests their protection could be important against Omicron.

Since the Thanksgiving holiday, concern has grown worldwide over the appearance of the Omicron variant, which shows signs of increased contagiousness compared to other COVID-19 variants. Originally reported in South Africa, there are now case reports in over 50 countries, and at least 19 US states, so far.

The new finding from the Africa Health Research Institute (AHRI) in Durban, South Africa, is in some ways reassuring for people who have had both their shots and a past COVID-19 infection, said outside experts, and suggests raising booster shots as a priority. But the finding — which experts caution is preliminary — raises concerns for those whose initial vaccination-induced antibodies may be waning.

“I think we're in a situation where we all hoped we would be reporting something different,” said Harvard Medical School’s Jacob Lemieux.

“But the reality is that the data suggests this is a more transmissible virus with significant degrees of immune escape, that is going to render the vaccines less effective, and most of the monoclonal antibodies ineffective, coming in a surge upon a surge at a really challenging time,” Lemieux said, citing concern about a variant-enhanced surge as holiday travel increases ahead of Christmas and New Year’s.

In the new study of blood samples taken from a dozen people previously vaccinated with the Pfizer-BioNTech mRNA vaccine, researchers led by AHRI’s Alex Sigal found that their antibodies were not sufficient to “neutralize” the variant in half of them — those who had never had an infection before.

However, half of the study participants had previously been infected with COVID-19. Of those six participants, five of them saw “relatively high neutralization” against the variant.

New work from AHRI's @sigallab strongly suggests that the SARS-CoV-2 #Omicron variant escapes antibody immunity induced by the Pfizer vaccine, but that considerable immunity is retained in people who were both vaccinated & previously infected.

Twitter: @AHRI_News

Sigal said in a tweet that the result was “better than I expected for Omicron,” showing that the variant was still vulnerable to vaccines overall and that it infected cells in a manner similar to other variants. In showing that the variant only incompletely evaded vaccines, the study also suggested that shots should remain effective against severe disease, especially when supplemented with a booster.

That said, the results overall reported a 40-fold drop in antibody activity against the Omicron variant as compared to vaccine antibody neutralization of the original SARS-CoV-2 strain of coronavirus, a much larger evasion than was seen from other variants.

The blood plasma study is still a preprint and has not yet gone through peer review by other scientists, raising some caution, but not enough to outweigh its newsworthiness, said experts.

“I think there's consensus among us that even though the numbers are small, that they're coming from a reputable lab that's done this before and are not surprising,” said infectious disease expert Bruce Walker of the Massachusetts Consortium on Pathogen Readiness.

“The effects are not subtle. So it's likely to be correct.”

Earlier on a White House briefing, National Institute of Allergy and Infectious Diseases chief Anthony Fauci had described very preliminary reports from South Africa of increased transmissibility of the variant as evidenced by increased cases of reinfection among those previously infected by the Beta and Delta variants there.

Fauci also described “very preliminary” study results, also from South Africa, that the Omicron variant tended to produce less severe disease than past ones. “Hopefully in the next few weeks we’ll get a much clearer picture,” he said. “But it appears that with the cases that are seen, we are not seeing a very severe profile of disease. In fact, it might be — and I underscore might — be less severe, as shown by the ratio of hospitalizations per number of new cases.”

A much more transmissible but only slightly less dangerous version of COVID-19 would still overwhelm hospitals in a heightened surge, noted Lemieux, the Harvard Medical School researcher. In past surges, death rates have increased as hospital intensive care units have filled up.

Skip to footer