forever.
The immune system is complicated. Protection can change over time, viruses evolve, and individual immune responses differ.
The WHO explains that protection against severe COVID-19 and death is highest during the first months after vaccination and then decreases over time. Immunity can also decline after infection, which is one reason health authorities periodically reassess vaccination recommendations.
That means someone who was vaccinated previously may not have exactly the same level of protection months or years later.
And the virus itself has changed.
What Is a Breakthrough Infection?
A breakthrough
