Although early findings suggest that the omicron variant is a milder form of SARS-CoV-2 infection, the severity of illness — particularly in different populations by age and underlying conditions — is still an unknown.
It is intuitive that those not infected previously or vaccinated would be at some higher risk of initial infection and possibly more severe complications. If the omicron variant turns out to be consistently mild even in those who are unvaccinated, we will be at a revelatory inflection point in the global pandemic. For now, all bets are off. COVID-19 vaccination and boosting are being widely encouraged by public health officials in the United States to prevent severe disease and hospitalization. However, as of this report, there were little data on the clinical outcomes of omicron infection in the unvaccinated. It was also unknown whether those infected with the new variant will retain some immunity against reinfection.
If omicron attacks the unvaccinated population like the delta variant, the result could be a surge in hospitalizations and deaths. According to Centers for Disease Control and Prevention (CDC) data regarding delta, unvaccinated people have about a six-fold increased risk of infection and are 14 times more likely to die than those vaccinated for SARS-CoV-2.1
The delta variant still represents almost all cases in genomic surveillance in the United States and appears to be surging again even as omicron has been reported in more than 25 states. As of Dec. 7, 2021, 89% of U.S. counties were reporting high (80%) or substantial (9%) COVID-19 transmission.2 In CDC genomic surveillance data as of Dec. 11, 2021, delta represented 97% of isolates, with 2.9% listed for omicron and 0.1% as “other.”3
On Dec. 10, 2021, there were 120,967 new COVID-19 cases, 1,310 deaths, and 63,995 hospitalizations as the United States approached the 800,000 deaths mark.4 Those daily totals represent a 38% increase in cases, a 26% increase in deaths, and a 22% increase in hospitalizations over the prior two weeks.
“Forget about omicron — we still have a major problem with delta,” Carlos del Rio, MD, distinguished professor of infectious diseases at Emory University in Atlanta, said at a recent briefing held by the Infections Diseases Society of America.
Whether omicron will supplant the delta variant and become the predominant SARS-CoV-2 strain in the United States remains unknown, but the initial signs from South Africa suggest that omicron might dethrone the reigning variant by sheer transmissibility. It seems to be rapidly becoming the predominant variant in the African country and genomic testing has been increased. The United Kingdom and some European nations expect Omicron to overtake delta in the near future.
Although there have been no large omicron outbreaks in the United States as of this writing, the CDC reports that some of the early U.S. cases “indicate community transmission.”5 Given the variant’s transmission traits and the global epidemiology, it appears almost certain that that there is much more omicron in the United States than public health officials have reported. Currently about 90% of COVID-19 case isolates in the United States are not subjected to the genomic analysis necessary for strain identification, so much more testing is needed, del Rio said.
Even if the saving grace of less severe disease holds true, there is thin line between increased severity and increased transmissibility, as the latter enables the virus to extend its reach to highly vulnerable populations. As of this report, broad evidence of that phenomenon was not being reported — at least concerning transmission to vulnerable people who would be expected to experience more severe infections. In any case, the basic infection control measures used against delta also should be effective against omicron, although there may be less margin for error given its high transmissibility.
“We certainly are not panicking,” says Ann Marie Pettis, RN, BSN, CIC, president of the Association for Professionals in Infection Control and Epidemiology. “It’s stay the course and keep promoting what we have been promoting. [That includes] educating the public about the safety of and the need for the COVID vaccines that we have. And the need for boosters because of waning immunity. We continue to promote the other mitigation efforts that we have been recommending from early on — face masks, social distancing, and avoiding large indoor gatherings when able.”
REFERENCES
- Centers for Disease Control and Prevention. COVID Data Tracker. Rates of COVID-19 cases and deaths by vaccination status. https://covid.cdc.gov/covid-data-tracker/#rates-by-vaccine-status
- Centers for Disease Control and Prevention. COVID Data Tracker. COVID-19 integrated county view. https://covid.cdc.gov/covid-data-tracker/#county-view
- Centers for Disease Control and Prevention. COVID Data Tracker. Variant proportions. Updated Dec. 11, 2021. https://covid.cdc.gov/covid-data-tracker/#variant-proportions
- Allen J, Almukhtar S, Aufrichtig A, et al. The New York Times. Coronavirus in the U.S.: Latest map and case count. Updated Dec. 13, 2021. https://www.nytimes.com/interactive/2021/us/covid-cases.html
- CDC COVID-19 Response Team. SARS-CoV-2 B.1.1.529 (Omicron) variant — United States, December 1-8, 2021. MMWR Morb Mortal Wkly Rep 2021; Dec 10. doi: http://dx.doi.org/10.15585/mmwr.mm7050e1. [Online ahead of print].
Although early findings suggest that the omicron variant is a milder form of SARS-CoV-2 infection, the severity of illness — particularly in different populations by age and underlying conditions — is still an unknown.
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