dаta: CDC dashboards and state Covid dashboards. Dani Alberti/AxiosAccording to data compiled by NBC and the Centers for Disease Control and Prevention, 125,000 Americans have been diagnosed with breakthrough infections and 0.001% have already died.Why it matters: Although "breakthrough" cases have attracted media attention, low numbers indicate that the pandemic is mainly a threat to the unvaccinated.Axios Markets delivers market news that is worth your time. Register now for a free subscriptionThese numbers don't include asymptomatic cases among those who were vaccinated, or for those who didn't get tested. The CDC tracks only deaths or hospitalizations.NBC noted that the number of breakthrough cases could be higher because nine states didn't have any information, while eleven states (like Florida) did not provide totals for death and hospitalization.In a recent report, the CDC stated that "V]accination [is] the most important strategy for preventing severe illness and death."Unpublished research by the CDC showed that the Delta variant can cause more severe illnesses in people who have not been vaccinated and spreads just as easily as chickenpox.The numbers are: Only 0.004% have been admitted to hospital after being vaccinated. .00% have died.The big picture: CDC data show that more than half of all Americans are still not fully vaccinated. The number of cases nationwide has increased since June.Editor's Note: This story has been updated to clarify that only breakthrough cases that resulted either in death or hospitalization are included in the CDC data.The headline has also been updated to reflect that 125,000 people had tested positive for breakthrough infection. However, this number does not necessarily represent all cases. This number does not include cases that are not symptomatic in those who were vaccinated, or those who were not tested.You liked this article? Subscribe to Axios Markets and get more information from Axios.