Mith the delivery of the first Covid-19 vaccines adapted to the omicron variant BA.1, hope for a completely renewed corona immune protection is germinating not only with Federal Minister of Health Karl Lauterbach – and, once again, some confusion. We evaluated current studies and answered five questions.
Do the new vaccines really protect better against omicrons?
The first two omicron vaccines from Biontech/Pfizer and Moderna approved by the European regulatory authority Ema are bivalent, i.e. they are directed against two different virus strains: against the original virus and against the BA.1 subtype circulating at the beginning of the year. The first vaccines adapted to the currently circulating Omikron BA.5 – also bivalent vaccines – are to be delivered by the end of this month.
According to the most recent comparative studies, these two Omicron-adapted vaccines are similar as boosters, at least as far as preventing severe Covid courses is concerned. In this respect, they are superior to the older vaccines, at least initially, but they are not much better either. In other words: Even those who have only recently been vaccinated with one of the conventional vaccines are very likely to be protected against a severe course of Covid 19 – the main thing is to get boosters. The two new vaccines from Biontech/Pfizer and Moderna can be used in people aged twelve and over who have received at least the basic immunization against Covid-19.
When does the booster vaccination work best?
Basically, the further back the last vaccination or infection, the more sensible it is to have a booster. The immunity curve automatically flattens out over time. After three or four months, the amount of antibodies and the activity of the immune cells decrease to such an extent that the omicron virus, which is notorious for its pronounced immune escape, is already much more likely to trigger acute Covid symptoms and severe courses.
According to the recommendations of the Standing Vaccination Commission (STIKO) and most expert committees abroad, a fourth dose (second booster) is also recommended for people over the age of sixty and vulnerable people. A booster vaccination and thus a high level of neutralizing antibodies and immune cells not only protects better against infection and disease in the initial period, but also demonstrably protects against the late effects of an acute infection, the long and post-Covid, which can sometimes last for months.
Should one wait for the more up-to-date omicron vaccines?
The vaccines adapted to Omikron BA.5 are in the approval phase and should come a few weeks after the BA.1 vaccines. They have the advantage that they are tailor-made for the currently circulating variant. However, BA.1 and BA.5 are not so far apart in terms of their antigenic profile that the superiority would weigh heavily.
In general, all Omikron-adapted vaccines have proven themselves as boosters in recent studies – provided they are administered in the ideal time window, i.e. with the necessary distance from one another. A lot doesn’t necessarily help a lot. Anyone who boosts themselves with the new BA.1 vaccine today should wait at least two months, and STIKO even recommends six months before the next booster. The situation is similar with an infection that has gone through, regardless of whether it is mild or severe: Anyone who has only recently come into contact with the virus or has been vaccinated has so many effective antibodies and active immune cells that an additional booster can only provide a small and little lasting extra boost triggers.
Should one use the same vaccines as before for boosters?
As far as the so-called hybrid vaccination is concerned, i.e. immunization with different vaccines or vaccine plus infection, it was clear even before the adapted vaccine was approved: hybrid beats homogeneous. According to a recent study, three different vaccines (or two vaccines plus infection) produce the most pronounced and longest-lasting immunity. Anyone who has had an infection not too long ago is also better protected against a new infection, because the mucous membranes in the nasopharynx have only had intensive contact with the virus surface molecules in the case of an infection. As a result, a special type of antibody (type A) is produced there in large numbers.
The viruses are caught by them almost immediately after infection and before they penetrate the internal organs. Next-generation vaccines should also offer such “sterile” immunity. In addition to other vaccines adapted to variants, there are therefore more than half a dozen vaccines in clinical trials that are administered as a nasal spray or by inhalation. India and China were each the first to circulate these vaccines, most of which were developed on the basis of vector vaccines or weakened viruses.
Can the vaccines also protect against new variants?
This depends above all on how strongly the virus variants then circulating differ genetically from the previous variants or how similar they are to the previous virus strains in terms of the immunologically decisive surface molecules. In any case, the “Centaurus” subvariant BA.2.75, recently brought into play as a potentially new dominant omicron, has proved in laboratory experiments to be sufficiently similar to BA.1 and BA.2 that it apparently does not exhibit a greater immune escape than the current omicrons. The current vaccines should therefore protect against severe Covid-19 for a while even if “Centaurus” spreads. There are currently no concrete signs of another more problematic virus variant.
