Read the article which was published in April 2022. It doesn’t say that it has anything to do with adverse effects.
It says that it’s not time yet for those aged 60-79 because their vaccine remains effective.
WhatsApp message received on 24 July 2022.
Singapore MOH: Second COVID-19 booster not recommended for people aged 60 to 79
All the adverse effects must be surfacing. Now U turn.