"They started in order with the eldest first and now they are up to people in their 40s."
- "They started in order with the eldest first and now they are up to people in their 40s."
"they started in order with the eldest first" 「年齢の上から順に進んでいて」
"they started" 「始まった」
"in order" 「順番に」
"with the eldest first" 「年齢の上から」
"and now they are up to people in their 40s" 「今40代まで来た」
"and now" 「今」
"they are up to ~" 「〜まで来た」
"people in their 40s" 「40代」・「40代の人」
The vaccination process is progressing by age, and we've now reached people in their 40s.
『年齢の上から順に進んでいて今40代まで来た』という文は、The vaccination process is progressing by age, and we've now reached people in their 40s. と表現できます。
ここで、progressing by ageは「年齢の上から順に進む」ことを示しています。また、reached people in their 40s は「40代の人々に達した」という意味になります。
このような状況に関して、以下の表現も使えます：
The rollout started with the oldest and has now come to the 40s.
We've progressed through the ages, and now it's the 40s' turn.
オーストラリア 
アメリカ合衆国 
