Does lack of aspiration explain covid vaccine adverse reactions?

Yes - according to Marc Girardot's bolus theory

What is aspiration and why is it important?

If a vaccine is intended to be injected into a muscle (“intramuscular IM”) rather than into a vein (“intravenous/intravascular IV”, i.e. directly into the blood stream) then, to avoid accidental injection into a vein, the technique of aspiration has traditionally been applied. This very short video by John Camp…