The virus has changed — and continues to change
. Viruses evolve. This is not a flaw in science; it is a fundamental characteristic of biology.
Since 2020, the virus responsible for COVID-19 has undergone multiple mutations, giving rise to new variants that behave differently from the original strain.
Here are some important changes:
increased transmissibility
Partial ability to evade immunity
Different symptomatic patterns
Variants like Omicron and its sub-lineages have demonstrated a crucial point: even strong immunity acquired through vaccination or prior infection may not completely block infection, especially in the upper respiratory tract.
However – and this is essential – protection against severe forms of the disease has remained much more stable.
Immunity is not a permanent shield.
Another reason why vaccinated people can still get sick is that immunity naturally decreases over time.
After vaccination:
Antibody levels reach a peak
Then a gradual decline
Memory cells are preserved for long-term protection
This means that several months after vaccination, your body may no longer be as effective at preventing infection, but it can still react quickly to fight the virus.
This is why booster doses have been introduced: to “stimulate” the immune system and strengthen protection, particularly in vulnerable populations.
