Jamaican Jackson withdrew from the 100m to focus on the 200m, in which she is the two-time reigning world champion, but did not line up on Sunday morning.
Jackson’s withdrawal from the competition means American Gabrielle Thomas, the fastest woman in the 200m this year, is the gold-medal favourite in the event.
Tokyo Olympics bronze medallist Thomas, 27, took world silver behind Jackson last year and began her campaign in Paris by setting the fastest time of round one in 22.20.
Less than 14 hours after celebrating a historic gold, Alfred, St Lucia’s first Olympic medallist, returned for the opening 200m heat and took another victory in 22.41.
Just as Jamaican sprint icon Shelly-Ann Fraser-Pryce’s withdrawal on Saturday left the race for the 100m medals wide open, so to has Jackson’s decision not to participate in the 200m.
Reigning champion Elaine Thompson-Herah, of Jamaica, had been ruled out of defending her two sprint titles in Paris because of an Achilles tendon injury.
After her near-miss in the 100m in pursuit of a first individual global medal, Neita refocused to make a confident start to her 200m bid as she cruised to victory.
“It feels like I went to sleep here [at the track] last night. It has been a quick turnaround,” Neita told BBC Sport.
“Fourth was so bittersweet. I’ve had a little sleep on it and honestly I’m really proud of myself. It gives me so much confidence and a lot of motivation going into tomorrow.”