If the infection figures drop sufficiently in the coming weeks, the caretaker cabinet wants to relax with a different deployment of the corona pass. Now all locations where the corona pass applies, such as catering, football stadiums and gyms, are also allowed to enter unvaccinated after a negative test (the ‘3G’ model). The government wants to change that. In environments with a high risk of contamination, such as unplaced events and catering, 2G should apply: only vaccinated people and people who have been cured from corona will then still have access. This would be safer and could prevent certain sectors from having to remain completely closed to vaccinated people as well.
Also read: The 2G regime will not turn the tide now
Politically, the choice for 2G is highly controversial. Outgoing Health Minister Hugo de Jonge (CDA) is expected to submit a bill to enable 2G to the House of Representatives this Monday, but it is still unclear whether a majority will support this. Many parties fear a further dichotomy between vaccinated and unvaccinated. The parties also wonder whether 2G does not provide a false sense of security, just like the current 3G. Vaccinated people do not need to test, but they can carry and spread the virus. For this reason, the ChristenUnie proposed last week to look at a 1G model, in which vaccinated people also have to test again.
What can be said about the security of the three different regimes for the corona pass? The Outbreak Management Team (OMT) met last Friday about the different variants. TU Delft made a risk model that calculates for the variants how many infections and hospital admissions result directly from an event. Researcher Bas Kolen used a fictional seven-hour unplaced dance event with 100,000 visitors and looked at what happens when it is held with a 1G, 2G or 3G regime. The cabinet and the OMT partly base their choices on his model.
The current infectious Delta variant has now been calculated in the model, the reliability of the rapid test in advance is estimated at 80 percent. The model also assumes good QR control. No distinction is made between vaccinated and cured people, because their protection against the virus is almost the same.
2G: Only vaccinated and cured people inside, no one tested
In this scenario, all 100,000 visitors are vaccinated or cured, but not pre-tested. It follows from the model that in such a case about 200 visitors are contagious. They can carry the virus unnoticed or have gone to the event despite complaints. In this scenario, the virus spreads less easily than among unvaccinated people. “In the model we have taken into account that vaccinated people are 60 percent less contagious,” says Kolen. Despite this, due to the lack of a test, some vaccinees will still take the virus inside and spread it. Kolen’s calculation shows that about fifty new infections would arise at the dance party.
2G is better than the other regimes to prevent attendees from having to be admitted after the event. The number of new admissions is negligible at 0.05. The reason for this is simple: vaccinated people rarely go to hospital after being infected and in a 2G setting they cannot encounter and infect unvaccinated people who do run a serious risk of becoming seriously ill.
In conclusion, Kolen says that with 2G, “the effect on infections is smaller than on hospital admissions”. He says it is therefore important to consider the precise goal of your policy: 2G is not a panacea for reducing or keeping the number of infections low. Incidentally, the model only looks at the risk at the event itself and not at the consequences afterwards. “People who have attended a 2G event go home and can still infect others who could end up in the hospital. That applies to every regime, but you have to take that into account.”
3G: Vaccinated and cured people are allowed in, unvaccinated even after a negative test
The 3G model is how the corona pass is already being used in many places. That system is certainly not watertight, it turned out in recent weeks. Despite the QR checks afterwards, about a thousand infections were still detected at a major event such as Amsterdam Dance Event. That is not surprising if you are going to calculate with 3G. For the fictitious dance party with 100,000 visitors, TU Delft assumed a degree of protection of 75 percent. In other words, 75,000 people are vaccinated or cured and 25,000 are unvaccinated. This last group does a test beforehand.
Calculations show that there are more infections at the event with 3G than with 2G: approximately 75 instead of 50. The majority of the group of infectious people at a 3G event is fully vaccinated. That makes sense, says Kolen. “Vaccinated people are by far the largest group, so also the largest source of infections.” However, they are less likely to infect each other, with the result that unvaccinated people in particular are at risk of a 3G event. Although they do a test beforehand and therefore usually do not come to the party with the virus, they run a relatively high risk of being infected indoors by a vaccinated person. Of the 75 new infections, more than forty occur in the small group of unvaccinated people.
3G also causes significantly more hospitalizations than the other regimens. Unvaccinated people who become infected are more likely to end up in hospital. In addition, there is also the risk that they will be relatively often in contact with other unvaccinated people after the event. 3G therefore works less well than 2G or 1G against infections and hospital admissions. So while it may be the most practical or just system politically, 3G is the least effective against further spread of the virus.
1G: Vaccinated, cured and unvaccinated people are allowed in, everyone tested negative
In a 1G system, vaccinated, cured and unvaccinated people are allowed to enter and everyone is tested beforehand. That seems to be an ideal way to prevent infections at the event, because this is the only model in which the large group of vaccinated people is also required to take a test. The TU Delft calculation shows that 1G does indeed lead to the fewest infections at the event: about 25, half less than with 2G (50) and three times less than with 3G (75). The fact that 25 infections can still occur is because the method of testing with an effectiveness of about 80 percent is not perfect: one in five visitors tests false negative or was still infected in the 24 hours between the test and the event.
If the goal of your policy is to prevent as many infections as possible, 1G is the best model, says Kolen. “1G will have the most effect on epidemiology because you capture more infectious people ahead of time.” 1G does lead to slightly more hospital admissions directly from the event than 2G. This is because at a 1G event there are unvaccinated people around and some of them can become seriously ill. Still, 1G will prevent more hospital admissions after the event, thinks Kolen. “Fewer infections afterwards means less risk for society, so 1G has a greater effect on what comes after the event, also in the hospital.”
Also read: 55 percent of the Dutch are in favor of 2G, but what do ethicists say?
1G can therefore be seen as the most secure model for the corona pass, but it is also a far-reaching system at the same time. The large group of vaccinated people will have to test again and again, which also requires a lot of extra testing capacity. “You have to test everyone again, and 100 percent safety does not exist with 1G either. Ultimately it is a question of how much risk you want to take and that is up to politicians.”
A version of this article also appeared in NRC Handelsblad on November 22, 2021
A version of this article also appeared in NRC in the morning of November 22, 2021