Omicron, Delta, and the Need for More Accurate Hospitalization Data

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Before the Omicron surge, the number of COVID-19 hospitalizations was increasingly being recognized as one of the most important metrics for a county or state to track its progress against the virus. Both San Francisco and Los Angeles County cited a low level of hospitalizations, deaths, and community transmission (along with high vaccination coverage) as the primary criteria that had to be met for consideration of removing the mask mandate, for example.


The one-month rise and near-dominance of the highly transmissible Omicron variant changed this conversation. Now, having an accurate account of COVID-19 hospitalizations is more important than ever. As Dr. Fauci recently said, we should focus less on the number of new infections and more on hospitalizations and deaths, and the medical community should operate on a focus on these two metrics.  We should not adopt a policy of marginalizing daily case numbers or stop tracking these carefully by health departments, of course, but our primary method of defining the success of our COVID strategies should be on lowering hospitalizations.


To do this, however, we owe it to the public health and ourselves to have better data on COVID-19 hospitalizations. This is even more critical as the U.S. is experiencing a higher level of hospitalizations relative to cases than has been observed in the United Kingdom and South Africa.


We noted with cautious optimism that the Republic of South Africa saw a peak to their Omicron surge after just 4 weeks. Published data also showed better outcomes of patients requiring admission for COVID-19-related illness relative to previous waves. One study showed that only 17.6% of patients required supplemental oxygen therapy versus 74% during the Delta wave. Only 1.6% required mechanical ventilation (vs 12.4%) and there was an 11% decline in those who required admission to the ICU. The median length of stay of Omicron hospitalizations was three days, while it was seven under Delta. These early indicators have significant implications for hospital resources and staff, which have been overburdened both physically and mentally for many months.


Some analysts pointed out that the affected population in South Africa – particularly in the epicenter of Gauteng Province – skewed younger and healthier, contributing to a perceived “milder” Omicron. However, subsequent age-controlled data from the Ministry of Health demonstrated that deaths among patients hospitalized for COVID-19 are two-thirds lower in this Omicron wave relative to the previous Delta wave. Adding to this, the largest real-world study to date out of the UK showed that those infected with Omicron were 50-70% less likely to require hospitalization than those infected with the Delta variant. Hospitalizations in London, and to an even larger extent ICU bed occupancy, appear on a sustained decline as well.


We now have six laboratory studies showing a decreased ability of Omicron to infect lung tissue, providing cellular level support that Omicron is less likely to cause the dreaded viral pneumonia prompting admission for supplemental oxygen or mechanical ventilation.


So why then is the U.S. seeing a surge in hospitalizations that looks poised to surpass last winter’s high? Possible reasons include the following:


Delta Is Still Out There

The Delta variant has not just vanished out of thin air. While Omicron has become the dominant variant in communities around the world, multiple regions of the U.S. – particularly in the Northeast and the Midwest -could be coming down from their Delta wave. As winter weather drove people indoors and the Holidays loomed, these areas were ripe for a re-surge in Delta-related hospitalizations.


As of last week, the Los Angeles County Department of Public Health was reporting that Delta was still responsible for 46% of new cases. However, the CDC now reports that new infections from Omicron are up to 95%, making it likely that Omicron will be replacing Delta everywhere in the US soon. .


Unhealthy Demographics

Another contributing factor is the U.S. population’s overall poor health and preponderance of chronic medical problems. Relative to the population of South Africa, a broader swath of our population is susceptible to severe illness from COVID-19 due to preexisting conditions such obesity, high blood pressure, emphysema, and other conditions. Even if Omicron is ultimately proven to be inherently milder than Delta, comorbidities can contribute to morbidity and mortality in the US.


The Accuracy of Our Hospitalization Data

Finally, how confident are we in our COVID-19 hospitalization data? We expect that hospitals now routinely test all patients requiring admission for COVID-19, regardless of whether they are being admitted for coronavirus-related illness or not. The reason for this is to isolate patients with positive COVID swabs, even if asymptomatic.


In a large study from South Africa, 63% of patients with Omicron on swabs admitted to the hospital were not symptomatic for COVID-19. So, knowing that so many South African were detected through testing and not symptoms, just how many COVID-19 hospitalizations in the U.S. are based on an incidental positive test when admitted for something else?


In fact, the chance for an incidental positive test would be greater in cities and counties with higher vaccination rates. While the most prevalent symptoms of COVID-19 are pulmonary, a COVID-19 infection can cause a range of pro-inflammatory or vascular symptoms, including heart attacks, strokes, or blood clots. The onus is certainly on us doctors – from the Emergency Room to the ICU to specialist consults like Infectious Disease – to test all patients and document accurately whether COVID is contributory to their illness.


As we now know, PCR tests can be positive for upwards of 90 days. Wouldn’t be better to be doing rapid antigen tests in the ER to identify those with an active infection? Most hospitals in the U.S. do PCR tests for admitted patients, including our own, but it is not standard across the board.


The United Kingdom is a leader in the detailed reporting of its hospital data. It recently found that 25-30% of its COVID-19 “hospitalizations” were incidental.


There are some leaders in reporting accurate hospital data here in the United States. Florida-based Jackson Health System reports daily how many of their admitted patients tested positive for COVID-19; and how many of those are admitted for non-covid reasons – recently as high as 50%. New York Governor Kathy Hochul this week ordered a clearer reporting and delineation of COVID-19 admissions as well. Los Angeles County-run hospitals reported that 2/3 of patients who tested positive for COVID-19 on admission were hospitalized for something else.  Marin County, the most vaccinated county in California, reported that 42% of COVID-19 positive tests for patients admitted to the hospital were incidental.


We propose that counties and/or states undertake a better accounting of COVID-19 admissions that would be reported to the CDC at the national level. Ideally, delineation of COVID-19 positive cases would include the following:

  • Incidental: not related to reason for admission

  • Nosocomial: not detected on admission; became infected during admission

  • COVID-19-related: the primary reason for admission


UCSF Hospitals report additional information on hospitalizations which would be very helpful for medical experts and policymakers:

  • Acute care

  • ICU – not on mechanical ventilation

  • ICU – requiring mechanical ventilation


Further specifics on hospitalization – in particular the percentage that require ICU level of care and mechanical ventilation – are proving to be a very important metric. U.S. hospitals, even in current wave epicenter New York City, are seeing approximately just 64% of their hospitalized patients in ICU beds relative to last winter’s surge.


And yes, while we need to continue to push hard for people to get their vaccine doses, we cannot rely on vaccine outreach alone. We must also make oral antivirals as widespread as vaccines and provide more at-home testing. Our call for more detailed hospital data isn’t just for the sake of having it. The efficacy of these approaches all hinge on accurate data; it informs our state and national pandemic responses and allows resources to be allocated accordingly.


But for now, we are flying blind without better data on hospitalizations.


Michael Daignault

Dr. Michael Daignault (@dr.daignault) is a board-certified emergency room physician at Providence Saint Joseph Medical Center in Burbank, California.



Monica Gandhi

Monica Gandhi MD, MPH is Professor of Medicine and Associate Division Chief (Clinical Operations/ Education) of the Division of HIV, Infectious Diseases, and Global Medicine at UCSF/ San Francisco General Hospital. She also serves as the Director of the UCSF Center for AIDS Research (CFAR) and the Medical director of the HIV Clinic at SFGH (“Ward 86”).


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