This is just a hypothetical excercise. Also, epidemiology experts will tell you from a pure health perspective but as a PM/President you'll need to consider economic factors as well. What you weigh more though is totally dependent on you.
As I understand it, the PM of Sweden doesn't have the authority to do anything you describe, due to https://en.wikipedia.org/wiki/Ministerial_governance , and (in)famously "The Swedish Constitution legally protects the freedom of movement for the people, thus preventing a lockdown in peace time." quoting https://en.wikipedia.org/wiki/COVID-19_pandemic_in_Sweden#Ec...
Are you sure your question isn't more like "if you were the dictator, what could you do?"
Also from Sweden is "Vision Zero" for road safety. https://en.wikipedia.org/wiki/Vision_Zero .
> A core principle of the vision is that "Life and health can never be exchanged for other benefits within the society" rather than the more conventional comparison between costs and benefits, where a monetary value is placed on life and health, and then that value is used to decide how much money to spend on a road network towards the benefit of decreasing risk.[2]
As a hypothetical exercise, how much monetary value do you place on human life? How do you rank economic factors over human life?
QALY (and in respectively human life) can be measured in monetary terms. It has some problems but all healthcare systems in the world do this, some openly (as in the UK), some behind the scenes. But they all do.
This is a mind experiment where we all have the luxury of hindsight. Based on current knowledge I would also do almost the same what Tegnell did but with greater emphasis on protecting the risk population, elderly and others.
Also I would cooperate with Astra Zeneca and other pharma companies to start human challenge trials immediately to speed up vaccine development.
The question posed, and refined by me, is: if you were the PM of Sweden, what would you do in the scenario presented here? Nothing? Or would you have started changing the laws/constitution so you have more power?
As the follow-up question, how much monetary value do you place on human life?
You can find online how much the UK estimates QALY to be worth for treatment purposes. That would be the starting point I would use. I wouldn't try to overturn the field by wild changes thinking that many smart people before me had made very bad policy decisions.
And to be fair: No where in the original does it say to consider only economics. Economics will come back: People's lives won't.