Even the experts still don't know what could be causing these side effects, or why it would be similar between the two vaccines. However, when they want to inve

Even the experts still don't know what could be causing these side effects, or why it would be similar between the two vaccines. However, when they want to investigate it, what they'll be looking at is that both the Astrozenica and J&J vaccines use adenovirus vaccine technology, and the Moderna and Pfizer do not, so there could be something in common there that leads to the side effects. I think people only have guesses they aren't super confident in as to what that could be at present.