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"70% of the vaccinated population is not given group immunity"

“70% of the vaccinated population is not given group immunity”

The European Center for Disease Control and Prevention launched a new platform with forecasts for the evolution of the epidemic. A year later, at a time of more optimism, are they still necessary?

We still don’t know what will happen. The development continues to depend on many factors, on how the vaccination program, which depends on the supply, the intake, will evolve. We have to take into account the cyclical variables, that is, the variables appear, which variants replace others, if the vaccine is suitable for protection against disease in the case of new variants. It depends on non-drug measures such as confinement or the use of masks and how people behave when they are vaccinated. Therefore, there are still many factors that must be combined that influence the future development of the disease in Europe. So I would say that we are far from reaching the end or being able to take our hands off the wheel and say this will follow this expected path, we are definitely not there.

We have heard this uncertainty on the one hand, and on the other hand, the assurance that we will reach mass immunity in the summer when 70% of the population will be vaccinated. Where are we in the epidemic marathon?

The primary purpose of vaccination is not to obtain group immunity. The primary goals are to reduce stress in hospitals and prevent very serious conditions that lead to death. This differs from the fact that vaccination is primarily aimed at preventing transmission of the virus. Limiting the spread of the virus may be desirable, but in reality it will be very difficult to achieve, and if we keep getting new variants, we will not want to take our eyes off the ball.

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There is an argument that trying to completely stop circulation can backfire, because in this way the population, the most protective, ends up coming into contact with new mutations, as in the case of influenza.

It is a very complex topic, the level of circulation of the virus can influence the emergence of new variants. The virus is subject to evolutionary pressure: it may have more mutations when suppressed because it must compete with more. These kinds of things are not something that we can model in projections. Feature of this center The point is that there are actually many different models, which make different assumptions. Some take into account the new variables, others look specifically at the measures in place in countries at any given moment and others are just statistical: “This is the current trend, and if it continues, the line remains that way.” So we have a lot of scientists in many countries looking at the problem in a variety of ways and what we did was not just put these models together so that we can compare them on the same platform, but merge them into a common model, which allows to reduce uncertainty and get more accurate predictions. Even if we are at the end of this story, and we are not, it is an important platform, because there are always viruses and other threats that we should be aware of.

Measles, for example?

In the case of measles, it would be difficult to use such a form. There is a random component. We know that the likelihood of a disease outbreak when the vaccination rate is low, but, as in most places, we are very close to the herd immunity line (95% vaccinated), it depends a lot on the presence of an imported case and the behavior of the people. But, for example, it can be used for influenza or dengue fever. We have collaborated a lot with CDC in the USA in developing these tools. The CDC has been making flu forecasts for eight or nine years and we talked about it center Of these before the emergence of Covid-19. And that’s why we think having this community of people who know each other, creates work habits, has this platform is a very positive thing because it means we’re ready. It is a versatile tool that can be adapted. We are better prepared next time.

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In the meantime, going back a little bit, don’t you think we’d achieve mass immunity in the summer?

It is not the primary goal of vaccination. We are trying to prevent deaths and hospitals are overburdened. In fact, it is not even clear how many people would need to be vaccinated to achieve group immunity against this disease. When people give numbers …

70% of the population that has been vaccinated …

When you say 70%, an important assumption is made, which is that people mix in the same way. That is, when you leave the door of your building, it is likely that you will meet someone who is exactly the same or completely different as you, so that you will likely meet someone who lives in your building like someone who lives at the end of a building. Way. That he will be with different people today than he was with yesterday. It is completely unreal. People tend to interact in groups and within groups with similar people, for example of similar ages. So the idea that all people mix randomly is a misconception, and if we say immunity is 70%, we are basically open to outbreaks in communities where there might be many people at risk.

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