Like most other vaccines, Covid vaccines don’t act as a foolproof barrier to infection but rather as a fire alarm. The virus enters your body, vaccine-induced antibodies quickly recognize the threat, and they launch an all out attack to stop the virus from replicating and rid it from your system. Even though you may have technically become infected, the infection is non-productive and you never become symptomatic or ill. That is successful vaccine protection.
The challenge though, is time. Antibody levels generally spike immediately after infection or vaccination and then fall over time. All of us can expect our initial antibody levels to drop eventually, somewhere around five to eight months, but for some of us — those with weaker immune systems either from age or other illnesses — those levels may drop sooner and more quickly. We also know that our antibodies perform less effectively against some SARS-CoV-2 variants, even among the healthy. Against some variants, effectiveness drops just four months after the second dose.
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But more recent studies have shown that a third dose can significantly improve both the potency and breadth of neutralizing antibody levels, providing even greater protection against all known variants.
