For example, one could question the potential for autoimmune conditions due to the way the mRNA vaccine works and how the immune system typically targets multiple proteins on the cell. There's no data or studies our there about this longterm possibility or even the incidence of autoimmune antibodies produced by vaccination. This likely isn't a problem for the elderly since it can take years or decades to present/progress, and their value proposition is different than for younger people. It starts to get more questionable as the value proposition changes dramatically in the youngest age groups. The question of vaccinating one's child for covid is certainly a topic with a diverse set of opinions and very little data to perform a thorough longterm cost/benefit analysis.
