First vaccination, then infection: am I through with Omikron now, Mr. Kern?

Every immune response is different and our immune system is constantly learning anyway – even better with the virus than with the vaccination. Peter Kern, head of the Immunology Clinic at the Fulda Clinic, explains why antibody tests are useless and why you can sometimes get infected if you are well protected.

ntv.de: The other day I was boosted and a week later I had Covid, almost without symptoms. Am I through with Omicron now?

Peter Kern: Maybe with Omikron, never with Corona, but we’ll talk about that in a moment. First of all: congratulations! Infection after the booster vaccination is the best level of immunization one can currently get against the coronavirus. We all have to go there.

Really all?

The immunologist and internist Peter M. Kern heads the Department of Immunology at the Fulda Clinic and teaches at the Philipps University in Marburg.

We have to go there as a population, not every single one, but those with good immunization. It would be too general to say: anyone who has been vaccinated may become infected. Every immune system reacts differently. But we can say: If you are well immunized, you can become infected. This includes a strong immune system that has been well trained on Corona: with the first lesson – consisting of the first and second vaccination – and with the second lesson – that was the booster. Once these two lessons have been learned, the pathogen itself can come.

But, if I understand you correctly, not every immune system learns equally well – unfortunately.

There is everything immunologically: from people with a very competent immune system, which offers very good protection after just two vaccinations or an infection, to people with a weak immune system, which does not respond even after four or five vaccinations and who should therefore try not to become infected because they are poorly protected. An 80-year-old asthmatic on cortisone must never become infected, not even after two boosters. A healthy and vaccinated 30-year-old does not take any relevant risk with an omicron infection and does not burden the healthcare system.

But how does the individual know whether the immune protection is sufficient? Does measuring the antibody value help? Some pharmacies offer this.

That’s no use at all. The so-called antibody titer only says something about the amount, but nothing about the quality of these antibodies. However, the quality of the immune response is crucial. Determining this exactly using measured values ​​is possible but very time-consuming. It has nothing to do with the amount of antibodies. You can save yourself such a test.

So how are people supposed to know how strong their immune systems are?

This is an individual assessment that is best done by your family doctor. According to simple criteria: How old is the person? What previous illnesses does she have? What drugs is she taking that might suppress her immune system? How has the immune system worked so far? Based on these parameters, an assessment is already possible.

On balance, would it still be safer to avoid the infection?

The immunization against Corona, in other words what we are currently doing to end the pandemic, is an ongoing procedure, a process. The immune system will inevitably have constant contact with the coronavirus – or voluntarily with the vaccine – and is thus constantly retrained and its response improved. That’s why none of us are ever “through” with the virus. Even on first contact with it, the immune response builds as a process.

How exactly?

The immune system first develops many different antibodies and combat cells, the T lymphocytes, against the pathogen. In many recurring review loops, the best ones are selected and left over, the less good ones are switched off. That takes two to four weeks, then you have the best possible immunity at that point in time, which then lasts for a long time.

And now comes Omikron and is an immune escape variant.

Not really. The triple vaccination still protects very well against a severe course or even death, because the immune system also recognizes some things in Omicron that it has learned from other variants or from the vaccine. So if omicron comes and cannot cause a serious illness because we are already 80 percent protected by the vaccinations, then after the infection we may have over 90 percent protection because the immune response has been further optimized.

Sounds good.

In this way, the protection continues to increase. And when new mutations come, it is crucial how much they differ from the previous ones in terms of the immunological points of attack.

Where does our defense attack the virus?

The coronavirus has four major building proteins – the spike protein everyone is talking about and three others. Each of these four major building blocks has about 1000 sub-building blocks, the amino acids. And small groups of these amino acids are the level at which the immune system recognizes the virus.

And the immune system first attacks many of these amino acid groups? And then is evaluated?

To do this, it builds antibodies and T-lymphocytes against these groups of amino acids, but they don’t all work equally well, exactly. The immune system starts with a large number, then filters out a lot and in the end only leaves three, four, five answers that were particularly good. The infected person, whose immune system has learned from the whole coronavirus, then has immune responses against all four proteins available, i.e. a very broad defense.

And how does it work when our defenses don’t learn from the virus, but only from the copy, the vaccination?

The current vaccines only mimic the spike protein, so only one in four, and only a part of it. The immune system of the vaccinated only gets to know the sub-components of this one protein, it has a smaller selection than with the infection and less time to optimize because the vaccine stays in the body much shorter than the pathogen. That is why the immunization of the recovered person is better, it is simply broader than after a vaccination and also lasts longer.

Why do all vaccines rely on the spike protein?

Some amino acid groups there are particularly important because the virus uses them to dock onto the human cell and penetrate. If they are destroyed by the antibodies, this is a particularly good protective effect. Vaccination can do that.

The next mutation will probably come in a few months. How does our defense react then?

When the virus mutates, some sub-building blocks change. If exactly those are changed against which the immune system has developed its response, then you have lost. If the immune system has left over responses against, say, three sub-building blocks, and a new variant has all three sites different, then the immune system sees nothing. Then it starts all over again.

Great.

But that is extremely unlikely. If we look at omicron: Of the 1000 sub-building blocks of the spike protein, 30 have changed from delta to omicron. 30 out of 1000. The probability is not very high that an immune response trained on Delta can no longer recognize anything because its defense mechanisms were only geared towards sub-components that are among the 30 changed. It is much more likely that someone who is now going through the infection with Omikron will still have a certain immune response against a variant that will appear in the autumn. This probability is greater than in a vaccinated person.

It sounds like infection instead of vaccination is also an option to become immune.

I would strongly advise against that. Yes, the most effective learning sessions happen through infection. But these are also the most dangerous, so they should not happen without vaccination protection. At some point the virus will come, millions of people who are infected despite all precautionary measures and vaccination are experiencing it. But that’s not bad, it’s the natural course. That will leave an even better immune response, and if that quality decreases again with time or mutations, we can boost it with vaccinations. Anyone who now hears about the procedure with the flu has understood it.

Should my well-vaccinated family have taken the opportunity when I was infected to also upgrade to the gold standard by infecting them with omicron? Instead of wearing a mask at home?

You can’t say that in general. If I live in a household with an elderly or immunocompromised person, I should definitely not do this. Personally, I work in a specialized clinic. Of course I am exposed and I know that there is a high probability that I can get infected despite the booster and all protective measures. My wife and I have decided for ourselves at home: we will not isolate ourselves internally, but will get through it together. We are in good health, not so terribly old and have been vaccinated three times. We think the immune protection is good enough to ensure a weak course. You can decide that individually, I don’t think that’s negligent.

And as a society? How do we go about it wisely?

The more we all differ through increasingly individual immunological profiles and individual risk factors for a serious illness, the less useful it is to have a general rule that applies to everyone. We need to differentiate more in our measures. And now the first good therapeutic approaches can also be included.

Frauke Niemeyer spoke to Peter Kern

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