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Omicron Variant: What Do We Know So Far?

Dec. 20, 2021

A COVID-19 variant unlike any others that was detected in South Africa at the end of November prompted countries around the world — including the United States — to take swift action in slowing transmission.


The cause for concern? This variant—B.1.1.529, or the omicron variant—has several mutations, and some early signs show that people who have previously had COVID-19 may still be susceptible to this strain.

What little was known of the omicron variant was enough for the World Health Organization (WHO) to classify it as a Variant of Concern on Nov. 26, 2021.

Scientists are studying the omicron variant to understand the threat it poses, but more information is needed before we can fully answer that question.

“We do know that the number of mutations places this strain genetically distant to the other variants like alpha, gamma and delta,” said Carl Fichtenbaum, MD; professor in the Division of Infectious Diseases in the Department of Internal Medicine at the UC College of Medicine; and a UC Health physician.

Pharmaceutical companies and vaccine manufacturers Pfizer-BioNTech and Moderna have stated that early data suggest a booster dose following two doses of their respective vaccines are effective in preventing infection by the omicron variant.

Dr. Fichtenbaum and other UC Health experts will continue to monitor news from the WHO.

“Over the next few weeks, there are likely to be preprints of articles that describe the variant, its response to treatments and how effective vaccines are against the variant,” he added.

Who discovered the omicron variant?

The variant was first reported from South Africa to the WHO on Nov. 24, 2021, though the first confirmed case was from a test performed on Nov. 9.

The discovery came amid increased cases of COVID-19 cases in South Africa.

But that doesn’t necessarily mean the variant originated in South Africa, according to Dr. Fichtenbaum.

“We do not yet know the origin of this virus,” he said. “It is likely that this variant exists across the world but that we first identified it in South Africa.”

Like many other strains, scientists hypothesize the omicron variant circulated in people whose immune systems are suppressed and who are less likely to “clear the virus” from their bodies, Dr. Fichtenbaum said.

“This allows the virus to further adapt and mutate,” he said. “Most of the time, the virus mutates and dies. But sometimes the mutation has characteristics that give it an advantage, like the delta variant.  Time will tell if omicron is going to cause extensive problems or not.”

The omicron variant is named after the 15th letter in the Greek alphabet, the equivalent to the letter “o” in the Latin, or English language, alphabet.

Similar to the naming of hurricanes, COVID-19 variant names are selected in alphabetical order.

“There have been a number of Variants of Interests that utilized prior Greek letters that have not become prevalent,” Dr. Fichtenbaum said.

Understanding Variants of Interest and Variants of Concern

Over time, all viruses mutate. Some new strains don’t significantly impact the way the virus acts, but some do.

As part of its ongoing monitoring of COVID-19, the WHO has established the labels Variants of Interest (VOI) and Variants of Concern (VOC) to allow countries to adequately respond to any potentially harmful strains.

A VOI is defined as a strain that meets both the following criteria:

  • It has genetic changes that could affect contagiousness, disease severity, vaccine effectiveness and other characteristics.
  • It has led to increased community spread or caused clusters in multiple countries, with increased numbers of cases and prevalence.

A strain is upgraded to a VOC if it meets the criteria for a VOI, plus at least one of the following:

  • It is more contagious.
  • It causes more severe disease.
  • Public health measures such as vaccines, tests and treatments are not as effective.

The omicron variant is one of five variants the WHO currently classifies as a VOC, in addition to alpha, beta, gamma and delta. The delta variant accounts for almost every case of COVID-19 in the United States. It’s characterized mostly by increased contagiousness and increased disease severity.

The Centers for Disease Control and Prevention (CDC) also has labels for variants it monitors. The CDC definitions for VOI and VOC are similar to those of the WHO.

However, the CDC has a label that the WHO does not: Variant of High Consequence (VOHC). In addition to meeting the definition of a Variant of Concern, a VOHC is defined by the following:

  • It isn’t detected well enough by tests (doesn’t meet testing targets).
  • There is a significant reduction in vaccine effectiveness, an unexpectedly high percentage of vaccinated people have been infected, or vaccines don’t protect well against severe disease.
  • Treatments are significantly less effective.
  • It causes more severe disease and increased hospitalization.

No variants are currently designated variants of high consequence.

How contagious is the omicron variant?

Scientists aren’t sure yet how contagious the omicron variant is, but the CDC notes that it might be more contagious than other variants—including delta. The delta variant is more than twice as contagious as the original COVID-19 strain.

The WHO notes that South Africa is experiencing increased cases, but epidemiologists are trying to understand if the uptick is the result of the omicron variant, or other factors.

How effective are existing vaccines against omicron?

Three doses of the Pfizer vaccine proved in preliminary laboratory studies to be just as effective as the original two doses have been against the original COVID-19 strain.

The third dose produced 25 times the amount of omicron neutralizing antibodies shown in blood tests, compared to the two doses.

The study also found that two doses of its vaccine, the regular vaccine series, may still protect against severe disease from the new variant.

Pfizer-BioNTech is planning to develop a vaccine specific to the omicron variant that could be ready in March, if needed.

Moderna also stated that a third dose of its vaccine created 37 times the amount of neutralizing antibodies against the omicron variant, when compared with the regular two doses.

When recipients received a double dose of the booster, their number of neutralizing antibodies were 83 times higher than the original two doses.

Similar to Pfizer, Moderna vows to develop an omicron-specific booster, which it expects to test in clinical trials in early 2022. It will also continue to study the effectiveness of its boosters, including evaluating the impact of a “double dose.”

The CDC recently recommended the Pfizer or Moderna vaccines over the one-dose shot by Johnson & Johnson, citing vaccine effectiveness, safety and rare adverse events.

Johnson & Johnson will continue to be offered in the United States, and the CDC emphasized that any vaccine is better than no vaccine—especially as the delta and omicron variants continue to spread worldwide.

Data has not yet been released on the effectiveness of the J&J vaccine against omicron, but experts urge those who have received this one-dose shot to get boosted with Moderna or Pfizer to increase their protection.

Vaccines from manufacturers Pfizer and Moderna remain very effective in reducing severe disease and death against the delta variant.

How do we protect ourselves against omicron?

The good news is that we have the tools to protect ourselves from this new variant, and they’re the same that have protected us from all strains of COVID-19.

Dr. Fichtenbaum noted that COVID-19, specifically the delta variant, remains a threat in the U.S., and that we should continue to protect ourselves and others even if omicron hasn’t yet spread widely.

“There is an uptick in cases through the United States and in Ohio/Kentucky. Transmission is still occurring at high rates,” he said. “Individuals should avoid indoor gatherings where possible, wear masks and use good hand hygiene.”

Whether or not you travel for the holidays, it would be wise to practice methods that reduce your risk of infection.

“The risk of infection will be highest when individuals gather indoors, eat or mingle with individuals not wearing masks,” he said. “The highest risk will be for those who have not been vaccinated.”