they aren't trained nursed giving the boosters
Are you sure about that, none of them are trained? Not a single one of the hundreds of thousands of people across the world, giving vaccines, know what they are doing?
The 3 that have vaccinated me all seemed extremely competent.
But, if some still need more convincing that vaccines are safe ....
Blood vessels, (ie not veins or arteries, which are not found in the upper/outer deltoids where injections are given), are smaller than the needle, so it is not possible to accidentally stick the needle into a tiny blood vessel. This part of the body is chosen for intramuscular injections because it is so suitable for them - it's not for the convenience of the person giving the vaccine. Refer back to the diagram I shared earlier.
Anybody here had a BCG injection? Remember that - jabbed in the arm. Every boy in school. We survived.
With regards to increase in heart problems, this was discussed in the thread about athletes having heart attacks - exposure to coronavirus, and long covid, has been shown to cause long-term heart issues. We can't just blame the vaccine, that is saving millions of lives now, for heart issues, when we already
know that coronavirus can cause the same problems. Maybe covid cases were higher in the country that was mentioned above (I've forget again, Sweden, Denmark ... ) - there could easily be another explanation for differences in the data.