Officials at the Governor's Office of Emergency Services announced Wednesday that there were immediate appointments available for vaccines at the federally operated site at Cal State L.A., regardless of eligibility.
But by 9 a.m. Thursday morning, it all changed and people were being turned away.
The OES told Eyewitness News that appointments for eligible people filled up overnight. That meant those who didn't have an appointment, ages 18-50, would not be able to receive a vaccine as previously thought. That's a problem the site hadn't encountered all week.
Many who headed to the site with a sense of relief that they might be getting their shot quickly grew frustrated.
"We've been waiting in line for about an hour now...a little over, a lot of people have been," said Dan Marcus of Studio City. "(We were told) it was okay to come in here. We get to the front of the line and now they're telling us we have to make appointments and we're not eligible for the shot."
Thursday's situation is a stark contrast from Wednesday, when people got in with no issues.
"Oh the process was great, my gosh, it was so quick," said Anthony Marquez. "(I) got in line at 4:44 p.m. and I was on my way home at 5:22 p.m."
Officials say they will prioritize appointments made through the state's website, My Turn.
Before those appointments quickly filled up, L.A. County's public health director said it was likely the result of scheduling issues, not a sign of dwindling demand.
Barbara Ferrer also said that even if there is a sudden wide availability of appointments, it doesn't mean the county should immediately expand eligibility to everyone aged 16 and over, which is scheduled to occur April 15.
"There's 5.5 million people in (currently) eligible groups, and all of them have not received their first dose,'' Ferrer said. "... We only opened for people 50 and older a few days ago, so we're going to continue to make sure there's good access.''
LA County officials urge vaccination before COVID-19 variants gain foothold
The county Department of Public Health even announced online the availability of vaccination appointments for Thursday at its county-operated vaccine sites, particularly the large-scale site at Six Flags Magic Mountain.
But Ferrer noted that appointment slots often open in waves, since sites can't list available appointments until they are assured of their supply of doses.
"One of the dilemmas here is that we're still struggling to be able to actually release appointments ahead of time, and many of us really are still only able to release appointments a couple days in advance of when ... people can go and get vaccinated,'' she said. "We're really trying to work hard to get a smoother forecast moving forward.''
Often when people go online and find a wealth of available slots, "it's because somebody just opened up a host of appointments,'' Ferrer said.
She said health officials monitor activity at the various vaccination sites, and if appointments aren't filled, capacity is increased at other sites with higher demand. She said the county is "looking into what might explain why at some sites we have more availability this week,'' but she said vaccine doses are not going unused. She noted that the county generally administers about 95% of the doses it receives within seven days.
"The goal here is always, and we've been great about this ... (to) get vaccine into people's arms within a seven-day period, and we are never carrying over a vaccine one week to the next,'' she said. "And we've always met that goal.''
She said she did not foresee a reversal of that trend this week, despite a sudden surge in appointment availability.
"Until we start seeing a problem this week with actually filling appointments for the rest of the week, I would say we're on a pretty good path to making sure those doses are actually administered,'' she said.