Those saying the risks are minimal, you don’t know the long term risks, nobody does, only the initial risks.
Please read this extract from JCVI:
The available evidence indicates that the individual health benefits from COVID-19 vaccination are small in those aged 12 to 15 years who do not have underlying health conditions which put them at risk of severe COVID-19. The potential risks from vaccination are also small, with reports of post-vaccination myocarditis being very rare, but potentially serious and still in the process of being described. Given the rarity of these events and the limited follow-up time of children and young people with post-vaccination myocarditis, substantial uncertainty remains regarding the health risks associated with these adverse events.
Overall, the committee is of the opinion that the benefits from vaccination are marginally greater than the potential known harms (tables 1 to 4) but acknowledges that there is considerable uncertainty regarding the magnitude of the potential harms. The margin of benefit, based primarily on a health perspective, is considered too small to support advice on a universal programme of vaccination of otherwise healthy 12 to 15-year-old children at this time. As longer-term data on potential adverse reactions accrue, greater certainty may allow for a reconsideration of the benefits and harms. Such data may not be available for several months.