Denmark: SSI 4th National COVID Prevalence Study & Reopening Risk Assessment

 

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Denmark peaked with their COVID Pandemic in mid-December with just over 3,200 cases a day being reported.  Since then, their numbers have declined, with their most recent 7-day average being 764 cases, a bit off their lows in early February, but fairly constant. 

Like many countries, Denmark is anxious to reopen their society, and they have announced plans to  allow concert venues, theatres and cinemas to open on May 6th. Additional phased relaxations will occur during the month of May. 

While lower daily COVID case totals are an important indicator, there are other metrics that help researchers evaluate the risk of reopening society. Prime of among them, the presumed level of community immunity to the virus. 
While prior infection or vaccination don't guarantee immunity, they are viewed as reasonably good indicators, at least in the near term.  How long immunity lasts from either is currently unknown (see Denmark SSI: Assessment of Protection Against Reinfection with SARS-CoV-2).

Today Denmark's SSI has published a risk assessment on the reopening of Denmark, along with their 4th National COVID Prevalence study. 

Our first stop is the prevalence study, which finds that nearly 20% of the population (over the age of 12) has either been vaccinated, or has detectable COVID antibodies.  This is far from what is assumed to be needed for `herd immunity' (i.e. 70%-80%), but is a significant increase over their last survey.

The number of covid-19 infections has increased significantly, according to the fourth national prevalence survey

The fourth national prevalence study shows a marked increase in Danes who have been infected with covid-19 and formed antibodies. This indicates that 7.0% of the Danish population has now been infected with covid-19. The latest prevalence survey in early December showed that 3.9% of Danes had been infected with covid-19

Last edited 4 May 2021

In order to be able to follow the spread of the covid-19 epidemic in the population, a study is periodically made of how many Danes have antibodies against new coronavirus.

This provides a measure of what proportion of the Danish population has already been infected with covid-19. It is the Folketing that has decided that the survey must be made. It is performed by the Statens Serum Institut (SSI) within the framework of TestCenter Danmark.

Now the results of the fourth round of this study are ready. They cover the months of March and April of 2021.

What does the study show?

The study indicates that 7.0% of the Danish population over the age of 12 had been infected with covid-19 at the beginning of March 2021. This would correspond to 325,000-375,000 people over the age of 12 having been infected since the beginning of the epidemic. This is a significant jump upwards from the previous study, which showed that 3.9% of the population had antibodies.

"The part of the population that has antibodies against the covid-19 virus has, as expected, increased significantly since the last survey from the end of November. It reflects that there was a lot of infection in the community over the winter. ” says Steen Ethelberg, who is a senior researcher at SSI and has been involved in conducting the study.

If we add the vaccinated proportion of the population to the proportion of the population that has been infected with covid-19, the study shows that 19% of the Danish population had antibodies against covid-19 in March 2021.

The study also suggests that in the first months of the year, for every time there were two people positive in a covid-19 test, there was only one undetected infection. It is significantly lower than previously estimated.

“The Danish test activity is very high, and it actually looks as if we have found most of the infected people in Denmark with the testing. Every time three people have been infected, the two of them have actually been tested positive. This means that there are fewer undetected infections than before. This is very positive, as chains of infection can thus be broken, ”Steen Ethelberg continues.

 

Want to know more about the survey?

You can read more about the fourth prevalence survey and the new results here .

See the note: The results from the 4th round of antibody testing with 50,000 extracted citizens, week 9-12, 2021

The fifth prevalence survey will be launched on 14 May.

The links to the SSI's risk assessments follow, after which I'll have some excerpt from their risk assessment:

SSI's risk assessments in connection with the reopening of Denmark

In connection with the new plan for the reopening of Denmark, the Statens Serum Institut has provided advice and a number of qualitative risk assessments to support the political considerations and decisions. Below are links to the three risk assessments

Last edited 4 May 2021

The Statens Serum Institut (SSI) views the agreement on further reopening of the country positively.

“We are pleased that a broad-based reopening has now been agreed, and we are pleased that the corona passport and the strategy for local efforts with closures are part of the agreement. With this extended reopening, we step on the accelerator, but do it knowing that the brakes are working, and it is crucial that we do not put the disease control out of control, "says Henrik Ullum, director of the Statens Serum Institut.

Risk of infection when lifting additional restrictions Read the risk assessment here:

Health professional assessment of phasing out restrictions in connection with the reopening plan for 6 May (pdf)

18 reliefs and consequences for the spread of infection

Read the risk assessment here:

Health professional assessment of individual reliefs in connection with the reopening plan for 6 May (pdf)

Additional reopening scenarios

Read the risk assessment here:
Health professional assessment of further reopening scenarios in connection with the reopening plan for 6 May (pdf)

Below you'll find the (translated) summary from Health professional assessment of phasing out restrictions in connection with the reopening plan for 6 May (pdf).

It isn't exactly a ringing endorsement of a rapid reopening strategy, and warns (repeatedly) of the myriad things that can go awry, and the need to be able to `adjust' the reopening strategy and timetable going forward. 

While Denmark is arguably in a better position to reopen than most other countries, success - depending, of course, on how you measure that - is far from guaranteed.   You can read the caveat-heavy assessment (bolding mine) below.

 
Overall assessment 

The Statens Serum Institut (SSI) has been asked for a professional contribution with a view to assessing risk of infection by lifting further restrictions as part of the further reopening The covid-19 epidemic has been stable over a long period of time with largely stable infection rates as well a stabilization of new admissions and inpatients, which means that the observed development continues stays below the level of the latest forecasts. 

This may be due to the massive testing effort and implementation of a model for automatic shutdown. There has been an increase in recent days in number of detected cases and an increase in the number of contacts, but it is too early to assess whether there are talk of random variation or a consequence of the recent reopening.

While the infection situation in Denmark is still stable, epidemic control is being challenged internationally the emergence of new, more contagious varieties. Several countries around Denmark experienced, especially in the weeks around Easter, worrying increases in infection that gave rise to the introduction of further restrictions, and more countries are experiencing health care pressures and excess mortality.

The situation looks very serious in several third countries outside Europe, including in particular India and Pakistan, which is currently experiencing an explosion in infection and a derived pressure on the healthcare system that is close on collapse. There are already many uncertainties associated with qualitatively assessing the potential risk of an increase in infection due to further easing.

But it is particularly difficult at present time when the effects of the openings on 21 April 2021, which SSI assessed would entail high risk for the spread of infection, can not yet be read with certainty in the number of infected or in admission numbers. SSI's professional assessment up to the negotiations on the previous reopening was made against the background of a stable development in the epidemic over several weeks and a period without major nationwide relief.

The recently implemented reductions include both school and the education area, outdoor and indoor sports for children, outdoor and indoor dining as well assembly ban. Some of the relaxations include areas that the professional reference group has assessed to be associated with a high risk of infection (bars and pubs, relaxation of assembly bans).

In a new assessment of further relief, in the same way as in the most recent assessment, continue to make reservations that increased activity in different sectors will interact with each other, and that it is not possible to fairly quantify these indirectly derived effects both in relation to other new reductions as well as in relation to the reductions already introduced. For example, relaxation of the assembly ban contributes to people to a greater extent meeting across social networks in extension of other activities, such as education, sports, physical attendance at work, or cultural activities.

Thus, greater interaction across networks and sectors, such as it is not possible to incorporate in an overall assessment of the risk of infection increase. It is also noted that further easing of restrictions will signal diminished concern in the authorities, which may give rise to changing behavioral patterns of the population in step with a diminished threat picture. This can lead to further spread of infection through increased socialization across networks as well as reduced compliance with recommendations for infection prevention efforts, which must be expected to challenge existing epidemic control.

Mobility data from DTU and data from HOPE is already showing signs of behavioral changes in the population in relation to an increased number of contacts across networks and increased traffic activity over recent weeks. Overall, the speed of the reopening process challenges the possibility of truthfully quantitatively that assess derivative contagion effects of increasing activity in the community in a situation where the effects of it recent major reopening cannot yet be assessed.

SSI therefore continues to consider that the reopening should take place carefully and step by step so that changes in infection can be responded to quickly, especially in light of the easing happens at such short intervals. In particular, reliefs that are expected to carry the least risk should be avoided increase in infection is a priority, which includes activities with limited volume as well as limited risk for interaction across facilitation.

Overall, it is estimated that a reopening with large, and for quickly implemented easing, increases the risk of the need for major local shutdowns to maintain control of the epidemic. In parallel with the step-by-step reopening, a lot should take place detailed monitoring of both key epidemiological indicators and close monitoring of behavioral indicators and activity data so that behavioral changes can be addressed with intensive communication. In addition, a model for local shutdowns should be maintained as a mechanism to control epidemic development.

          (Continue . . . )

 
The good news in all of this is that Denmark's testing and surveillance programs are top notch, and they should be able to pick up any signs of significant backsliding relatively quickly.