Pandemic Endgame: Danish Epidemiologist's Prediction

An earlier post, "Coronavirus Geography: Denmark Could Be an Omicron Harbinger," noted that experts pointed to three countries where the Omicron variant was causing infections to surge in mid-December. An update on Denmark follows.

"Speaking to Danish TV 2, Tyra Grove Krause—the chief epidemiologist at Denmark's State Serum Institute—said a new study from the organisation found that the risk of hospitalisation from Omicron is half that seen with the Delta variant," reports Chris Jewers for the Daily Mail on Jan. 3.

This, she said, has given Danish authorities hope that the Covid-19 pandemic in Denmark could be over in two months.

'I think we will have that in the next two months, and then I hope the infection will start to subside and we get our normal lives back,' she said on Monday.

Another major finding of the Danish study was the primary reason for the rapid spread of the Omicron variant. What was most surprising was what it found about transmission in fully vaccinated households in the Omicron wave. Scroll down to the final two sections below, beginning with "Transmissibility vs. immune evasion."

The Statens Serum Institut operates under the auspices of the Danish Ministry of Health and is charged with ensuring preparedness against infectious diseases.

Endemicity ahead

"Despite early fears that Omicron could prolong the pandemic due to its increased level of infection, Ms Krause said it actually could spell the end of the pandemic," adds Jewers.

According to the study: 'Omicron is here to stay, and it will provide some massive spread of infection in the coming month. When it's over, we're in a better place than we were before.'

"Living with the virus," as opposed to "defeating the virus," as President Biden continued to assert on Jan. 7, is to accept COVID-19 as an endemic disease. 

[See related post: Post-Pandemic: Living with COVID, January 31, 2021]

Population immunity will increase

"But while infection numbers in countries with the variant are soaring, the expert said that the highly infectious Omicron appears milder than the Delta variant, and therefore more people will be infected without having serious symptoms," adds Jewers.

As a result, she said, this will provide a good level of immunity in the population.

Krause is referring to population immunity, "defined as the proportion of the population that is protected against SARS-CoV-2 infection due to prior infection or vaccination," according to the American College of Physicians. While similar to herd immunity, it does not involve meeting a threshold when transmission of the pathogen ceases.

Denmark has 78% of its population fully vaccinated, according to The New York Times global coronavirus tracker on Jan. 8, the fifth-highest in Europe after Gibraltar, Portugal, Malta, and Spain. Nearly 48% of vaccinated Danes have received a booster shot, according to Reuters. The U.S. has 62% of its population fully vaccinated, with nearly 36% boosted.

World Health Organization agrees

"Ms Krause's optimistic comments came three days after the World Health Organisation [WHO] made a similarly hopeful statement about Omicron," adds Jewers.

'If we put an end to inequality, we will put an end to the pandemic and the global nightmare that we have all gone through,' WHO chief Tedros Adhanom Ghebreyesus said in a speech on New Years Eve. 

Tedros is referring to vaccine equity. WHO Incident Manager Abdi Mahamud told Geneva-based journalists on Jan. 4, "The best way to reduce the impact of the variant would be to meet the WHO's goal of vaccinating 70% of the population in each country by July, rather than offer third and fourth doses in some countries," reported Reuters.

Cases are surging more rapidly than last posted

Denmark had the world's third-highest case incidence on Christmas Day, as noted in the aforementioned post:

The 7-day average of daily new cases in Denmark approached 11,000 on Dec. 25, according to The New York Times global coronavirus tracker, up 77% in the last two weeks and 10% from what SSI reported (via CNN above) a week earlier. The daily case incidence was 184 per 100,000 people, the third-highest in the world after San Marino and Andorra, both of which have higher vaccination levels than the U.S.

The surge has increased since Christmas. Daily new cases have increased to a 7-day average of over 18,000 on Jan. 8, an increase of almost 70% during the last 2 weeks, according to the Times tracker. While no longer on the tracker's 'top 10' list in case incidence, a sign that Omicron is becoming dominant globally, it is #14 with 311 per 100,000 people.

U.S. COVID update

By comparison, the 7-day average of new cases in the U.S. on Jan. 8 is >650,000, up 226% from 2 weeks ago, according to the Times U.S. tracker. The daily case incidence is just short of 200 per 100,000 people.

As noted in a recent post (under the header, "Two health metrics to watch closely"), the hospitalization rate is more important to follow during the Omicron wave. Hospitalizations have increased to a 7-day average of almost 125,000, the second-highest since the pandemic began, surpassing the Delta wave peak of 103,000 set on Sept. 4, 2021, but still below the 2020/2021 winter surge record of 137,500 daily average hospitalizations set on Jan. 10, 2021.

The hospitalization rate is 38 per 100,000 people, a 75% increase from 2 weeks ago. Hospitalizations have increased in all but three states (Wyoming, New Hampshire and New Mexico) during the last 2 weeks.

It will get worse before it gets better

"Omicron will peak at the end of January, and in February we will see declining infection pressure and a decreasing pressure on the health care system," Kraus said, adds Jewers.

'But we have to make an effort in January, because it will be hard to get through.'

Omicron's increasing spread will continue to put pressure on Denmark's healthcare system, she said. 'This is definitely what will be the challenge in the future.'

Transmissibility vs. immune evasion

As posted earlier ("Your Date With Omicron"), scientists study three traits when a new variant emerges, as Dr. Ashish Jha, dean of the Brown School of Public Health, explained in a New York Times op-ed on Nov. 27, two days after South African scientists first identified the Omicron variant:

• Transmissibility
• Virulence
• "And third, will it render our immune defenses — from vaccines and prior infections — less effective (a phenomenon known as immune escape)."

While the Daily Mail and TV-2, the government-owned subscription television station, were quick to note the finding that that the hospitalization risk of the Omicron variant was half that of the Delta variant, resulting in Krause's prediction about the oncoming transition to endemicity, the focus of the study was on transmission of the variant, particularly within Danish households and comparison to the prior Delta variant.

The study, "SARS-CoV-2 Omicron VOC Transmission in Danish Households," conducted by researchers at the University of Copenhagen, Statistics Denmark, and Statens Serum Institut (SSI), found that "the virus is mainly spreading more rapidly because it is better at evading immunity obtained from vaccines," reported  Nikolaj Skydsgaard for Reuters on Jan. 3.

"Our findings confirm that the rapid spread of the Omicron (variant) primarily can be ascribed to the immune evasiveness rather than an inherent increase in the basic transmissibility," the researchers said. The study has yet to be peer-reviewed.

The immune evasion was illustrated when comparing the transmission of the Omicron variant within vaccinated and unvaccinated households.

Startling finding on transmission within households

"The study found an increased transmission for unvaccinated individuals and a reduced transmission for booster-vaccinated individuals, compared to fully vaccinated individuals,"  states the three-paragraph summary of the study posted on SSI's webpage.

However, when comparing transmission within vaccinated and unvaccinated households (HHs), called the secondary attack rate (SAR) – when an infected  HH member spreads the virus to other members in the HH, resulting in secondary infections, the results were truly surprising.

The paragraph that deals with the SAR and secondary infections in the short abstract can be difficult to follow. It may be easier to understand the findings in the "Results" section on pg. 7 or 31 in the study PDF.

The highest SAR, i.e., the highest likelihood of household transmission, occurred in fully vaccinated HHs for the Omicron variant: 32%, as compared to 19% with Delta. In sharp contrast, not only was the SAR lower for unvaxxed HHs for Omicron, 29%, but the SAR was essentially the same for these HHs for the Delta variant, 28%, showing no noticeable change for the unvaccinated in transmission from the two variants.

Boosters decreased the SAR for Omicron for vaxxed members to 25%, just a bit lower than for the unvaxxed HH members.

In short, Omicron is a game-changer for households that are fully vaccinated when it comes to transmission during the Omicron wave – they are actually more vulnerable to infection from infected family members than unvaccinated households.

Related in Planetizen:

• Your Date With Omicron, December 29, 2021
• Coronavirus Geography: Denmark Could Be an Omicron Harbinger, December 27, 2021
• Post-Pandemic: Living with COVID, January 31, 2021