TrackTown USA, the Organising Committee for the event, confirmed it would allow spectators to attend, just over a month after reducing capacity at the Hayward Field track and field facility at the University of Oregon because of the COVID-19 pandemic.
It said vaccinated sections of the stadium, which has undergone a major facelift in time for the delayed World Athletics Championships, would “form much of the ticket inventory”.
Ticket-holders must provide proof of full COVID-19 vaccination in order to sit in a vaccinated section at the trials, due to take place between June 18 and 27.
Organisers have not yet confirmed how many fans will be allowed inside the venue, which has a capacity of over 12,000.
The change in policy has been made possible after the US Center for Disease Control and Prevention said fully vaccinated adults can safely resume indoor and outdoor activities without masks or distancing, including large gatherings.
“Oregon health regulations regarding stadium capacity have shifted significantly in the last two weeks,” said TrackTownUSA chief executive Michael Reilly.
“We are absolutely thrilled as these changes allow for previously impossible spectator numbers.
“Alongside our partners, we have developed a plan to maximise attendance while keeping participants and our community safe.
“We appreciate the hard work of public health officials and Government leaders who have made the announcement possible.”
The trials will be the first major event held at the revamped $270 million (£194 million/€223 million) Hayward Field facility and the first with a large crowd following the updated COVID-19 guidelines.
Organisers said all customers who retained their ticket orders through April 2021 will be able to keep their tickets, but their section could change to adhere to health regulations.
Fans who purchased tickets will still be able to claim a refund if they no longer wish to attend.
There had been strong interest in attending the trials, always one of the most high-quality athletics events of the year, especially with the opportunity to take in the renovations at Hayward Field.
The venue had been due to stage the World Athletics Championships this year before the event was pushed back to 2022 following the postponement of the Tokyo 2020 Olympic Games.