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There are still questions about the role of vaccine administration, which uses many different approaches. All advanced candidates will be administered intramuscularly. This leads to a strong production of IgG antibodies, which are actually formed quite late in the course of an infection. Although this type of antibody protects the lower respiratory tract, i.e. the lungs, this type of administration has no effect on the number of IgA antibodies formed earlier in the course of a respiratory infection. They are found mainly on the mucous membranes of the upper respiratory tract, where they inhibit the pathogen. Vaccination may protect the lower respiratory tract but not the upper respiratory tract.
“This can lead to vaccines that protect people from a symptomatic course, but still allow the virus to spread,” even if the likelihood of transmission was still reduced, Krammer said. If it still had active ingredients that can be administered through the nose, the upper respiratory tract would also be better protected. However, there are few such candidates.
Less protection from vaccination in the elderly?
So far, it appears that a naturally occurring Covid-19 infection leads to a “normal” immune response in which the number of antibodies to the pathogen decreases somewhat over time, but not dramatically. It is not known how long a vaccine of any type protects effectively, says the virologist. It could also be that vaccination protection is lower in older people who are at higher risk. On the other hand, many candidates have been able to trigger relatively strong side effects so far, raising question marks about use in children who are more susceptible to this.
