There is science behind changing the iso period now, Omicron is here

Last August, we watched in horror as Victoria announced a record-high 725 cases of COVID-19 in 24 hours. How times have changed. Today, Australians have to come to terms with more than 20,000 COVID-19 messages in one day. The true number is probably higher. This increase in cases, driven by the Omicron variant, has brought us to another crossroads in this chaotic journey: reviewing quarantine and isolation measures and definitions. The result, as has generally been the case with many aspects of this pandemic, will not be a perfect solution, but instead a potpourri of pragmatism and caution that will hopefully put us in the right direction.

The country's leaders largely agree on changes to insulation requirements and tests.

The country’s leaders largely agree on changes to insulation requirements and tests.

These changes are undoubtedly due to the unprecedented volume of cases that Omicron has presented to us and the subsequent implications of it, namely overwhelming of our test capacity, as well as the sending of several people to isolation or quarantine. Omicron can bypass vaccines and re-infect individuals who have already had COVID. In fact, a non-peer-reviewed study from Japan concluded that this cunning variant is more than four times more transferable than Delta. If so, this potentially makes Omicron the most contagious disease we’ve ever known – an insane concept. The only silver lining to this cloud of contagion, and the other reason for redefining isolation and quarantine, is Omicron’s seemingly reduced virulence. A South African press has also reported that infection with Omicron is generating an immune response to neutralize Delta, the variant that has been prominent for most of this year.

There is science behind the measure to reduce the isolation period for those with COVID-19. Most transfers of COVID-19 occur from between two days before symptoms occur and three days after. Viral excretion occurs in addition to this for a few more days, but at lower levels. In other words, a person with COVID-19 who was released from isolation on day five or seven could still transmit it, but the risk is much lower. The caveat here is that these apply to variants before Omicron, and perhaps Omicron behaves differently. For example, early data from the US and Norway suggest that Omicron has a shorter incubation period than Delta; Therefore, rules about leaving isolation that incorporate symptom duration must be considered. There are literally millions of Omicron cases worldwide now, so reliable data on viral excretion will soon be available.

One factor has not changed with our approach to Omicron: We must prevent the hospital system from being flooded by a tsunami of SARS-CoV-2. The mantra that a less virulent but more contagious variant can hospitalize more people than a more virulent, less contagious variant still holds true. While current NSW figures show that the percentage of active COVID-19 cases in the hospital is much lower than below the peak in September, the absolute figures are rising. In the last three weeks, COVID-19 hospital admissions have increased almost fivefold and now hover around 750. The NSW government has not said much beyond that these cases in the hospital are largely unvaccinated. In terms of determining easing of definitions and constraints, it is important to understand more about these inpatients in terms of Delta versus Omicron, age, risk factors, and booster status. Such data may have practical implications, such as further shortening the range to a booster dose or not changing the isolation or quarantine definitions for those who visit or work in geriatric care centers.

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In summary, in the current climate of Omicron, it is reasonable to redefine isolation and quarantine rules. However, this is not a signal to “give loose”: easing of definitions means that compliance with COVID-safe measures becomes even more important, not less. Mandatory indoor masks, QR codes, outdoor gatherings where possible and well-ventilated indoor gatherings where it is not will continue to be key strategies as we move into this next phase of the pandemic. Governments must be willing to change their strategies in response to the deluge of data that Omicron will generate in the coming weeks. All too often, this is perceived as confused backwards rather than a considered flexibility in the face of a changing situation and new information. One thing is for sure: Never say never with COVID-19.

Sanjaya Senanayake is an infectious disease physician and lecturer at the Australian National University Medical School.

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