The effectiveness of the corona vaccines is undisputed, even after evaluating real-world data in countries with high vaccination rates.

As in the clinical trials, it is excellent for all vaccines approved in Europe.

However, the effectiveness is not set in stone.

It subsides over time.

The crucial question is therefore: How quickly and how much does it disappear - and when does the vaccination have to be refreshed?

Joachim Müller-Jung

Editor in the features section, responsible for the “Nature and Science” section.

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    The Standing Vaccination Commission (Stiko) at the Robert Koch Institute is still officially covered, even if the Stiko chairman Thomas Mertens recently “2022 at the latest” as the date for a possible third (for Johnson & Johnson vaccine for a second) vaccination dose called. SPD health expert Karl Lauterbach brought the study situation to a different number in an interview: The vaccination protection is sufficient for most about six months.

    In fact, the assessments of vaccination experts currently differ widely - which is not due to the vaccines themselves, but above all to the high degree of individuality of the immune response. And the difficult to assess spread and effect of the virus variants with immune escape mutations. The “South African” variant, for example, and to a lesser extent the “Brazilian” and “Indian” variants, have mutations that weaken the effect of the neutralizing antibodies in the blood.

    However, none of the numerous studies so far has shown that the immune response is so severely impaired that protection against Covid 19 disease is lost.

    Nevertheless, the vaccine manufacturers are already developing “booster” doses and - like Curevac in Tübingen - “second generation vaccines”, which are also targeted against such variants.

    The vaccinated people hardly have to fear that they will become seriously ill after being infected with a variant.

    Immune response is different

    But it is also clear: The effective antibodies are gradually broken down in the blood, the immune and thus also the protection against infection dwindle. How quickly this happens depends on many factors. Among other things, how strong the immune response is after the vaccination. This was often observed in those who had recovered last year: the more seriously someone was sick, the stronger the immune response and the longer the immune system protected against further illness.

    In systematic studies with infected hospital staff, the pool of antibodies and immune cells was still sufficient after one year. And: vaccines usually produce a more pronounced immune response than an infection. The protection also depends on the vaccination schedule: A British study recently showed for the mRNA vaccine from BioNTech / Pfizer that - similar to the product from AstraZeneca - there is an interval of three months between the vaccine doses (instead of the usual six weeks) the number of neutralizing antibodies more than tripled. A booster vaccination may then be necessary later.

    It is crucial that in the double vaccination schedule, the second dose is by no means omitted.

    In those who have recovered - even if the Covid 19 disease was many months ago - a single dose of vaccine generates an excellent immune response.

    Most experts reckon that a third dose a few months later will again significantly accelerate the immune response and improve it in the longer term through the maturation of antibody-forming memory cells and T cells.

    Booster vital for cancer patients

    For immunocompromised people, and thus also for hundreds of thousands of cancer patients undergoing treatment and for organ transplants, the booster vaccination is even vital. Several studies have found that their immune system is often weak, even after two vaccinations. How long a “booster” then lasts remains open. A study by the Moderna vaccine manufacturer has shown that after the second vaccination dose, the neutralizing antibodies can be expected to drop to a seventh of the initial value after about eight months - with a strong vaccination effect this should still be sufficient, by fifty percent of the To prevent infections and almost all serious illnesses.

    According to the vaccine manufacturer, the decline in the protective antibodies then progresses at a much slower rate. This has not yet been confirmed with data. At least since this week there has been more clarity as to how the status of the immune protection can be clarified. In the journal "Nature Medicine", Australian immunologists have found that the measured amount of neutralizing antibodies in all known vaccines reflects the protection against mild to severe Covid-19 diseases almost exactly. It is therefore clear that monitoring the immune response with antibody tests can also make sense for people at risk.