Not sure if the risk/benefit ratio for vaccinating children is so clear-cut. A pre-print study from University of California, for example, "suggests that boys aged 12 to 15, with no underlying medical conditions, [might be] four to six times more likely to be diagnosed with vaccine-related myocarditis than ending up in hospital with Covid over a four-month period" [1].
The UK Joint Committee on Vaccination and Immunisation (JCVI) "is of the opinion that the benefits from vaccination are marginally greater than the potential known harms [...] 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." [2]
That's also why Pfizer announced that "long-term safety of COVID-19 vaccine in participants 5 to <12 years of age will be studied in 5 post-authorization safety studies, including a 5-year follow-up study to evaluate long term sequelae of post-vaccination myocarditis/pericarditis." [3]
[1] https://www.theguardian.com/world/2021/sep/10/boys-more-at-r...
[2] https://www.gov.uk/government/publications/jcvi-statement-se...