Thomas is the fastest woman over 200m this year, while Alfred is out to add to the 100m title she won on Saturday night.
Both stars comfortably won their 200m heats on Sunday morning - Thomas going fastest overall (22.20) - with Dina Asher-Smith and Favour Ofili also impressing at the Stade de France.
The repechage round takes place during the day on Monday (5 August) before the semi-finals are held later that evening. The women's 200m final is then 20:40 local time on Tuesday (6 August).
After a long and memorable night, Alfred was back out on the track on Sunday morning, albeit with a bend to navigate on this occasion.
In the absence of Marie Josée Ta Lou-Smith, who pulled up injured in the 100m final, Alfred cut a focused figure in the opening heat as she waved to the crowd before getting the done.
Racing for the first time as an Olympic champion, the Saint Lucian had the comfort of being able to slow down with 20m to go as Frenchwoman Gemima Joseph delighted the home crowd by finishing second.
News then started to filter through of Jackson’s withdrawal. The Jamaican was captured on the warm-up track in the shadows of the Stade de France on Sunday morning, but she did not enter the call room ahead of her heat.
Her DNS will undoubtedly have filtered through to her rivals, with 2023 worlds silver medallist Thomas going in the second heat and putting down a time of 22.20.
Gabrielle Thomas won her 200m heat on Sunday
With Jackson’s lane vacant in the third heat, Daryll Neita comfortably won and will know her chances of a medal have now increased – the Team GB star having placed fifth at the worlds last year, and finishing fourth in the 100m on Saturday night.
“I’m feeling amazing, it’s good to come out here after a short turnaround from last night. It’s an amazing atmosphere,” Neita told Olympics.com afterwards.
“The rain [last night] was like a bit of the UK wanted to come over and be a part of it. It was an amazing achievement for me coming fourth in the 100m final, which is such an incredible event, these ladies don’t wait around.
“It keeps me motivated. I definitely need to get rest, but I look bouncy and smooth. 100 per cent [the goal is medals], why not?”
It was then the turn of two more Americans to make a statement. McKenzie Long and Brittany Brown are the second and fourth fastest female sprinters respectively this year, and will be looking to challenge for gold – never mind just the podium places.
Up first, Long eased to victory in the fourth heat with a 22.55, before Brown responded in kind when winning the fifth heat in 22.38.
“[I’m] taking it one race at the same,” Ofili told Olympics.com. “Make sure you win your heat and that’s it. Having cheer for you also makes you want to be better.”