Note: This is an automated translation (using DeepL) of the original German article.
Analysis attests: PCR entry test and high vaccination coverage reduce infection risk from open air event
Simulation models are an ideal tool to answer “What if…?” questions. One such question is how to safely hold music festivals in times of a pandemic.
Results of the study at a glance
The study focused on the question of which strategy would detect as many infected persons as possible and thus break infection chains. For this purpose, the legally provided 3G strategy (entry only with proof of being infected, vaccinated or tested) was contrasted with a stricter testing strategy. In this stricter strategy “3G-PCR “ all persons who are not vaccinated or recovered must take a PCR entry test on site.
Firstly, it was shown that thanks to the stricter “3G-PCR” entry rule, a large proportion of infected persons are already fished out of the system at entry. As a result, the number of new infections detected by the antigen test 72 hours after entering the site is reduced by 40%. Secondly, a significant influence of the vaccination coverage among festival visitors can be observed. Thus, at a 70% vaccination coverage rate, the number of new infections confirmed at the festival decreases by over 40%, compared to a 50% vaccination coverage rate.
In addition, the rule of not having to be tested if vaccinated presumably provides an incentive for visitors to take up vaccination appointments. This is a positive aspect in that, especially for autumn, the highest possible vaccination coverage rate must be achieved to prevent an increase in the number of cases. It would therefore be ideal to actively promote vaccination in the run-up to the event in order to motivate target groups that are difficult to reach to be vaccinated.
In addition to new infections, the impact on the health care system is relevant. Here we see, especially by the composition of the age groups of the visitors, that only an (for the health system)insignificantly small number of people need medical care. This does not include further infections, e.g. among the elderly after the festival.
The simulation assumptions in detail
For the event - and thus the simulation - the specifications of the organizers were:
- The entire festival area (incl. camping zone) is cordoned off, visitors must prove 3G or “3G-PCR “ upon entry and remain in the area until departure. Staff can leave and enter the area according to general rules.
- Proof of 3G, or in the “3G-PCR “ strategy an additional PCR test for only-tested, must be provided prior to entry into the premises.
- 72 hours after admission to the festival site, any person admitted as “negatively tested” will be subject to antigen testing.
- The festival will take place from August 19 to 22 (4 festival days), with the 17th and 18th as arrival days and the 22nd and 23rd as departure days.
- 49,500 visitors are expected. These are divided between 83% Austrians, 17% Germans in the age group of 16-25.
- The festival will be shortened from 4 days (Thursday - Sunday) to 3 days (Thu-Sat) if necessary (in this case only the 22nd day will be departure day).
The entrance test will intercept a large proportion of Covid-infected individuals at the entrance. However, due to the diagnostic window, as well as the (very small) possibility of being infected shortly before entry despite vaccination or recovery, it is impossible to intercept 100% of all Covid-infected individuals.
With these assumptions, four different scenarios (each for the 4- and 3-day festival) were tested:
- 50% of festival attendees are vaccinated + normal 3G rule.
- 50% of the festival visitors are vaccinated + all only-tested have to do PCR test
- 70% of the festival visitors are vaccinated + normal 3G rule
- 70% of festival visitors are vaccinated + all only tested have to do PCR test
The number of new infections detected by antigen testing at the festival was compared and can be seen for the 4-day festival in figure 1. Results for the 3-day festival are not meaningful due to the limitations.
Fig.1: PCR entry testing at the festival removes a large proportion of infected individuals (yellow bars) from the system who might not have been tested if the festival had not taken place. In addition, a high vaccination coverage rate of 70% (versus 50% vaccination rate) drastically reduces the number of confirmed new infections.
- The number of confirmed cases is the proportion of infected persons found by testing and varies greatly among age groups. The remaining infected persons include the so-called dark figure. This was not reported.
- The study was calculated with the then current Covid forecasts (dated 6.7.2021). Due to the increased number of cases since then, the results must therefore be corrected upwards accordingly.
- The antigen test is performed 72h (3 days) after entry into the site. If the duration of the festival is shortened from 4 to 3 days, a large part of the visitors will no longer be tested due to the time of arrival and departure. This clearly reduces the number of new infections detected.
- For the calculated scenarios, a comparable seasonality as in July 2020 was assumed.
- The prevalence of the delta variant was considered in the simulation and will account for over 90% of cases in August.
- Other imported variants with potential escape mutations are not considered.