Many think: if they are vaccinated, they can do what they want afterwards without getting infected. Why is that not the case?
The antibodies in the bloodstream protect very well against serious infections. But there is still the “gateway” through which the virus comes: the nasopharynx. A small part of the antibodies is also there by the mucous membranes “gun at your feet” and secures this “entry gate”. However, if the number of viruses becomes too high, these local antibodies can no longer prevent a local infection in the nasal cavity.
You can’t have enough antibodies in your nasal cavity for antibodies to intercept every virus in such a case. Here the virus multiplies and the free viruses then attack the cells in the nasopharynx. These are the breakthrough infections, but they have almost no symptoms.
So if there are too many viruses, it can still lead to infections, despite vaccination?
Yes, but this is where vaccination is so important. The systemic antibody cells in the blood then prevent the infection from spreading further into the body and leading to lung damage.
As you can see, the antibodies can prevent a local infection up to a certain number of viruses. Breakthroughs occur with high viral loads. But then the vaccination prevents infections in the rest of the body.