We don’t know if MMR doesn’t but we still give kids[0] the vaccine in infancy. The vaccine is too young (<60 y old). So I suppose ask yourself what proof you need and why.
0: most kids, I just got the disease instead and the vax later
We do know MMRV causes more seizures in kids than MMR and countries (like Canada) still choose to administer the vaccine with riskier outcomes due to costs and the fact parents don’t like to come back for more shots.
0: most kids, I just got the disease instead and the vax later