The U.S. Centers for Disease Control and Prevention (CDC) has identified approximately 6,000 cases of Covid-19 infection among the roughly 85 million (as of 04/20/21) Americans who have completed a full course of vaccination.
A database of genetic tests from virus samples in these patients is being assembled so that scientists can analyze the frequency of each variant and hopefully clarify whether a booster or modified vaccine may be needed.
These so-called breakthrough cases, which are defined as positive Covid-19 test results received at least two weeks after patients receive their final vaccine dose, represent 0.007% of the fully vaccinated population. The risk of death from Covid following complete vaccination is approximately 0.0001% (one per million).
Not perfect, but pretty good odds.