Global Health Press

Multiple early studies find notable Omicron vaccine evasion

In quickly moving scientific developments over the past 24 hours, three separate labs that tested the Omicron (B.1.1.529) COVID-19 variant against vaccines reported significant immune escape based on reduced antibody titers, which were followed by similar findings from Pfizer that also suggest a third dose shores up antibody titers.

In other developments, the World Health Organization (WHO) in its weekly update said global cases were at a plateau last week for the second week in a row, though cases rose sharply in Africa—especially in South Africa and neighboring countries. And at a briefing, WHO officials said the Omicron variant has been detected in at least 57 countries so far.

A flurry of immune escape clues

Last week, global health officials predicted that researchers would work fast to shed light on the Omicron variant threat and how well countermeasures might hold up.

For early clues about impact on vaccines, researchers have been testing Omicron variant viruses (live or pseudovirus) in small numbers of patients’ blood samples and comparing antibody neutralization titers against either the original COVID-19 virus or the Delta (B1617.2) variant.

Yesterday, the first study came from a group at Africa Health Research Institute in South Africa, led by Alex Sigal, PhD, which found a 40-fold reduction in antibody neutralization, both in people who had two doses of the Pfizer-BioNTech vaccine as well as in people who had hybrid immunity from both natural infection and a dose of Pfizer vaccine.

A short time later, a team based at Sweden’s Karolinska Institute found a sevenfold reduction in blood samples from random donors and a fivefold reduction in samples from those who had earlier COVID-19 infections.

Virologist Sandra Ciesek, MD, a virologist and gastroenterologist with University Hospital Frankfurt, reported that her experiments showed a 37-fold reduction in neutralization against Omicron in the blood of people who had received three doses of Pfizer, when compared with Delta. She also found no measurable Omicron neutralization 6 months after two-dose regimens of Pfizer, Moderna, or a mix of Pfizer and AstraZeneca.

Then Pfizer released its preliminary findings, which suggest three doses of the vaccine neutralizes the Omicron variant, with the third dose increasing neutralizing antibodies 25-fold compared to two doses of the vaccine against the wild-type virus. The company said it is working on a variant-specific vaccine against Omicron, which it hopes to have available by March 2022, if needed.

Red flags, but vaccines likely help

Taken together, although the preliminary studies raise red flags, they also hint that Omicron’s escape from neutralization is incomplete. Several virology and epidemiology experts on Twitter commented on the new findings, which they said are concerning. However, some emphasized that a degree of neutralization was still present and that hybrid immunity (earlier infection and vaccinated) neutralized Omicron, a potentially encouraging sign for boosters.

At a WHO briefing, Kate O’Brien, MD, who directs the WHO’s Department of Immunization, Vaccines, and Biologicals, said, “Even with Omicron, I don’t think anybody expects that the vaccine, even in a worst-case scenario, would have no effect on a variant.” She added that the discussion hinges on what changes or adjustments there might be to vaccines, but not that they’re entirely ineffective.

Soumya Swaminathan, MD, the WHO’s chief scientist, said booster doses are probably not the solution, though officials are still looking at the evidence.

She emphasized that many countries, even those with ample vaccine supplies, have substantial portions of people who aren’t vaccinated. She said the benefits of reaching people who haven’t received their primary doses are likely to be higher than administering booster doses.

Global plateau for second week

In its weekly update on the pandemic, the WHO said cases last week remained at a plateau, though numbers were up significantly in two regions: Africa and the Americas.

Africa’s cases were up 79% from the previous week, led by South Africa’s surge in Omicron variant activity. Cases also soared in neighboring countries such as Eswatini, Zimbabwe, and Mozambique, though it’s not clear if Omicron, thought to be more transmissible, is playing a role. The WHO noted that the countries have very low vaccination rates, with about 12% of populations fully vaccinated.

Director-General Tedros Adhanom Ghebreyesus, PhD, said Omicron has now been reported in 57 countries, and it expects the number keep growing. “New data are emerging every day, but scientists need time to complete studies and interpret the results. We must be careful about drawing firm conclusions until we have a more complete picture,” he said.

He warned countries that complacency could cost lives. “Even though we still need answers to some crucial questions, we are not defenseless against Omicron, or Delta. The steps countries take today, and in the coming days and weeks, will determine how Omicron unfolds.”

Source: CIDRAP

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