What do systematic reviews say?

Inactivated influenza vaccine vs placebo or no intervention

Inactivated parenteral influenza vaccine showed no clear difference in nausea or vomiting assessed by subjective report Timing of… compared with placebo or 'do nothing' (low certainty).

• Vaccines for preventing influenza in healthy adults 2018 · Cochrane Headline outcomes only
  RR 1.8 [0.65, 5.04]
  4 studies · 6315 participants
  Low