First Choice Neurology

Delta Remains the Dominant Variant while Omicron Emerges

Omicron variant
Original image sourced from US Government department: The National Institute of Allergy and Infectious Diseases.

COVID-19 cases have increased 43% over the past two weeks and hospitalizations show a 22% increase, but is it the Omicron variant? More than 1,300 deaths are being reported each day, which is up 26%.

Numerous states are reporting double the cases from two weeks ago. Texas and Florida lead with the most COVID-19 cases. Texas cases are up 167%, and Florida is up 185% in the last 2 weeks.

The increase is driven by the Delta variant. It is unclear how the Omicron variant will affect the trends in the coming weeks. The Delta variant accounts for more than 99% of all U.S. cases. Reports show that the Omicron variant is very transmissible. Even if most cases are mild, a highly transmissible variant could result in enough infections to overwhelm health systems, the CDC cautioned.

Dr. Anthony Fauci stated that the Omicron variant can evade some vaccine protection, but booster shots can increase efficacy and offer more coverage.

Testing for Omicron cases has been primarily focused on travelers who are typically young and healthy, said Jennifer Nuzzo, DrPH, senior scholar at the Center for Health Security at the Johns Hopkins Bloomberg School of Public Health.

“The body of evidence that we have so far, which is very limited, suggests the potential that it may be more transmissible than the Delta variant,” she added. “We don’t yet have any evidence of increased severity.”

The scientific community’s understanding of omicron will change as it makes its way into older and more susceptible populations, Nuzzo said.


The Omicron Variant

What do we know about Omicron? On November 30, the United States designated Omicron as a Variant of Concern for which there is evidence of an increase in transmissibility, more severe, a significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures.

Omicron has some similar mutations in its spike protein to the Delta variant, according to the Republic of South Africa’s Department of Health, as well as the Alpha, Gamma, and Beta variants — all classified as variants of concern by the WHO.

Omicron has more mutations on its spike protein than the Delta variant does. The coronavirus enters our cells using its “corona,” or layer of protein spikes, then makes copies of itself in our bodies, where inevitably there are some errors or mutations, as explained by Yale Medicine. Sometimes those mutations in the virus are harmless, but other times — like in the case of the Delta and Omicron variants — they make it much easier for the virus to spread from person to person and infect more people.

Omicron significantly reduces the number of neutralizing antibodies from a 2-dose mRNA series compared to previous variants. This is because immune systems are adaptive and diverse.

Omicron cases are doubling every 3-4 days. There are also more breakthrough cases with Omicron. Vaccines and boosters continue to provide some protection, based on preliminary evidence, but is it enough?

Pfizer announced today that they created Paxlovid, a Covid pill that protects against severe disease, including the Omicron variant. Studies showed the pill reduced the risk of hospitalization and death by 89 percent if given within three days of the onset of symptoms. The drug jams into one of Omicron’s key proteins — called a protease — just as effectively as it does with other variants, Pfizer found.

Pfizer said that 0.7 percent of patients who received Paxlovid were hospitalized within 28 days of entering the trial, and none died. By contrast, 6.5 percent of patients who received a placebo were hospitalized or died.



It has been one year since the first vaccine dose was given in the U.S.  COVID-19 vaccines have proven to be highly effective in preventing hospitalization and death, with people who are unvaccinated being more than 10 times more likely to be hospitalized if infected. But no vaccine is 100% effective at preventing illness, so some people who are fully vaccinated against COVID-19 may still get infected.

However, vaccinated people who get infected with COVID-19 are much less likely to get severely ill or die from COVID-19 than people who are unvaccinated. 62% of Americans are fully vaccinated.

Vaccine makers are optimistic the current vaccines authorized for use in the US will provide a degree of protection against Omicron, too.

Earlier this week, the FDA authorized the first drug for widespread use in preventing Covid-19 in Americans with weakened immune systems, a group that includes blood cancer patients, transplant recipients, and people taking drugs that suppress the immune system.

The antibody treatment, Evusheld developed by AstraZeneca is engineered to last longer. The body metabolizes it more slowly so that it can stay active for months. That is expected to offer longer-lasting protection — perhaps for half a year — compared to the monoclonal antibody treatments that are given to high-risk people already sick with Covid.



Preliminary evidence shows that vaccine effectiveness against Omicron after 2 mRNA shots of Pfizer was 30-40% – but, a booster shot increased effectiveness to 70-80%. The U.S. has authorized COVID-19 vaccine booster doses for all Americans age 16 and older.

The National Institutes of Health (NIH) wrote that the initial results of studies conducted both in the lab and in the real world show that people who get a booster shot, or third dose of vaccine, might be better protected. Though these data are preliminary, they suggest that getting a booster will help protect people already vaccinated from breakthrough or possible severe infections with Omicron during the winter months.

According to the CDC, adults 16 and older, should get a Pfizer or Moderna booster if it has been at least six months since they completed the two-dose series with the Pfizer or Moderna vaccines. Adults who received the single-dose Johnson & Johnson shot at least two months ago should get a booster with any of the COVID-19 vaccines available.

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