Do you need the third dose of vaccine?

Three questions are waiting to be answered

1. How long does the vaccination last?
2. Do you have to refresh the vaccine protection and can you mix the vaccines for this?
3. How well do the vaccinations protect against new virus variants?

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And the antibodies dwindle …

The vaccinations are supposed to make the immune system fit against the virus. To do this, it produces antibodies that bind to the invading virus and render it harmless. But there are reinfections and it is also known that the number of antibodies decreases, in some cases quite rapidly. This escapes the hope that the cellular immune defense will compensate for this. It is “more elegant” than the antibodies floating around in the blood. You can count them and do serum tests to prove whether the antibodies are actually fighting the virus; while the immune cells only become active in the event of an infection.

Experience that has been made with immunity to other human coronaviruses shows that the immune response becomes weaker. With OC43, which causes colds, it lasts about a year. Coronavirus 229E produces antibodies, but not enough to protect against infection with Sars-CoV-2. Maybe it prevents severe gradients.

Many people with Covid-19 likely have had a history of contact with other human coronaviruses. One suspects up to 20 percent. With some, an increased production of antibodies (a kind of booster effect) was observed with a Covid infection, with others nothing at all. Sera from patients who had a 229E infection 8 to 17 years ago no longer responded to a current variant of 229E.

It appears that within a period of about six months after the second dose, the level of antibodies in the blood may drop below a level that will prevent infection. This speaks for the need for a booster vaccination.

Nothing speaks against a vaccine cocktail

Of course, scientists should answer the question of whether a third vaccination is needed, and not the producers. This also applies to the question of whether the vaccines can be mixed. Whether after two doses of Moderna a Pfizer booster works just as well as vice versa. Technologically, there seems to be nothing to be said against it.

Both companies are already experimenting with a further vaccine development that takes the new variants into account. In England, however, it has been observed that a mix of a Pfizer dose with one from Astrazeneca caused stronger and more frequent side effects. So it seems more sensible to use the same vaccine to which you once responded well.

And how is the race with the virus going?

What do the vaccinations do now? The preferred answer to the third question would of course be: the vaccinations are so good they will make the virus go away. The magazine “Nature” made a survey. 89 percent of the 119 scientists surveyed from 23 countries considered it to be at least “likely” that the virus will become endemic. That – like other infectious diseases – it will haunt us periodically. Only 14 percent considered it “very likely” that the virus could be locally eradicated (25 percent as “likely”).

The measles scenario would be conceivable. That would mean that regions would become Covid-free thanks to vaccination coverage and herd immunity, while outbreaks would recur in other regions. Or that the vaccinations protect so well and can be spread so widely that one would only have to reckon with mild courses. It’s like the way we deal with the flu.

There are differences, however. We do not yet know how Sars-CoV-2 will develop. As long as the incidence is high in certain countries, it will continue to mutate. And the 229E story is troubling. However, the spike protein of the coronavirus is not as versatile as hemagglutinin, the surface protein of the influenza virus, which plays an important role when the virus tries to penetrate a host cell. This evolutionary breadth of the influenza virus leads to the annual poker game with the vaccine. The mRNA vaccines used against Sars-CoV-2 are also much more flexible.

The syringes will be with us for a while

We have to come to terms with the fact that the two pikers are not enough. As long as the virus is rampant, there is a high probability that our immune system will not be able to keep the antibody level at the required level that no booster or other booster vaccinations will be necessary.

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