COVID-19 Roundup: Omicron’s ‘Doubling Time’ Concerns Health Officials; No Need for New ‘Specific Booster’; and More

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December 17, 2021


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With Doubling Rate of 2-3 Days, Omicron Will Likely Overtake Delta Variant, Experts Say

Some U.S. states are seeing record high hospitalizations as the Delta variant continues to be dominant, mostly among the unvaccinated. But researchers are now warning that Omicron likely spreads more rapidly.

The Omicron 19 variant, first detected in South Africa about a month ago, now makes up about 3 percent of cases sequenced in the U.S., according to the latest data this week from the U.S. Centers for Disease Control and Prevention (CDC). Rochelle Walensky, M.D., CDC director, has referred to Omicron’s doubling effect in media interviews, referring to the period of time the number of cases of the variant doubles in a given country.

“The science is still evolving, it’s still early, but what we’re seeing in some of these other countries is doubling times of about every two days or so, so really rapid increase in the amount of Omicron that’s out there,” Dr. Walensky said on the Today Show. She added that it could take a matter of weeks for Omicron to overtake Delta as the dominant variant. Delta has had a reported doubling time of at least seven days. 

The CDC states that anyone with Omicron infection can spread the virus to others, even if they are vaccinated or don’t have symptoms.

Last week, the CDC said no deaths have been reported among the 43 patients that have been followed up on. The most common symptoms so far have been mild, including cough, fatigue, congestion and a runny nose. Among those patients, 58 percent were between the ages of 18 and 39 years of age and 79 percent were fully vaccinated at least 14 days before symptom onset or testing positive.

It’s too early to tell if Omicron cases will remain mostly mild as it spreads, U.S. public officials say.

“The level of severity appears to be maybe a bit less than Delta –but there are a lot of confounding issues there,” White House chief medical advisor Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases, said in an ABC News interview. “It may be due to the underlying protection in the community due to prior infections, but these are just preliminary data that we’re going to have to just follow carefully to get them confirmed.”

Booster shots of both the Pfizer-BioNTech and Moderna vaccines seem to provide strong protection against severe illness from the new Omicron variant — although the initial two doses of each vaccine appear less effective than three doses.


Dr. Fauci: No Need for ‘Specific Booster’ — Third Shots from Existing Vaccines Highly Protective Against Omicron

It seems very likely that booster doses of both the Moderna and Pfizer-BioNTech COVID-19 vaccines offer a substantial increase in protection against the new Omicron variant, which by all accounts is more transmissible than the Delta variant, according to Anthony S. Fauci, M.D., President Biden’s top medical adviser on COVID-19.

During a presentation this week at the National Institutes of Health (NIH), Dr. Fauci said that “at this point, there is no need for a very specific booster” designed specially to fight Omicron. Existing boosters do the job of protecting the public from severe illness from both Omicron and Delta variants. Delta remains the dominant variant nationwide, but that may change within weeks because of Omicron’s higher transmissibility.

“Our booster vaccine regimens work against Omicron,” said Dr. Fauci, who is also director of the National Institute of Allergy and Infectious Diseases. “At this point, there is no need for a very specific booster. And so, the message remains clear: If you are unvaccinated get vaccinated, and particularly in the arena of Omicron if you are fully vaccinated, get your booster shot.”

Dr. Fauci cited a study from England that found two shots of Pfizer-BioNTech vaccine were 40 percent effective against Omicron, but that effectiveness jumped to 80 percent after a third shot, or booster. He also shared preliminary data from the NIH’s study of the Moderna vaccine that found two doses produced a less-than-optimal antibody response against Omicron, but that protection increased significantly after a third dose as well.

U.S. public health officials are trying to encourage everyone who is eligible — those 16 and older — to get their booster shots. As of Wednesday, about 27 percent of fully vaccinated Americans have had booster shots, according to the U.S. Centers for Disease Control and Prevention.


Study: Natural Infection Immunity and Vaccination Combined May Provide Best Protection

A combination of vaccination from COVID-19 and naturally acquired immunity from infection seems to provide the most robust antibodies against the coronavirus and its variants, according to new UCLA research.

The study’s findings, published in the peer-reviewed journal mBio, also indicates that COVID-19 boosters, now available for everyone 16 and older may be equally protective in fortifying antibodies to target variants, including the Delta variant, which is still dominant, and the new Omicron variant, which may be even more transmissible. While the study was conducted prior to the emergence of Delta and Omicron, the study’s senior author said in a news release that the results could apply to those and other new variants.

“The main message from our research is that someone who has had COVID and then gets vaccinated develops not only a boost in antibody amount, but also improved antibody quality — enhancing the ability of antibodies to act against variants,” said Otto Yang, M.D, the senior author and a professor of medicine in the division of infectious diseases at UCLA’s David Geffen School of Medicine. “This suggests that having repeated exposures to the spike protein allows the immune system to continue improving the antibodies if someone had COVID then been vaccinated.”

The virus uses spike protein to invade the body’s cells, resulting in infection. It remains uncertain whether the same benefits would be realized for people who have repeated vaccinations — but who have not contracted COVID-19.

The researchers compared blood antibodies in 15 vaccinated people who had not been previously infected with the virus with infection-induced antibodies in 10 people who were recently infected — but not yet vaccinated. Several months later, the 10 participants in the latter group were vaccinated, and the researchers then analyzed their antibodies again.  Most people in both of the groups had received the Pfizer–BioNTech or Moderna two-dose vaccines.

Research suggest that repeated vaccinations may be able to accomplish the same thing as getting vaccinated after having been infected — “although further research will be required to address that possibility.”

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