Attendances at the Africa Cup of Nations will be capped at 80% of capacity for games involving hosts Cameroon, and 60% for all other matches at the tournament.
The move by organisers Confederation of African Football (Caf) comes following consultation with the Cameroonian government regarding the ongoing coronavirus pandemic.
Spectators must be fully vaccinated and present a negative test result in order to attend games.
Just 2% of people in Cameroon have had both jabs, according to figures from Our World in Data, but reports indicate there has been an increase in the number of people in the country trying to get vaccinated so they can buy tickets for the Nations Cup.
"Caf will continue to monitor the situation and the evolution of the health conditions and adapt measures if needs be," said a statement from African football's governing body.
Cameroon open the tournament against Burkina Faso at the Olembe Stadium in Yaounde, which has a capacity of 60,000, on Sunday (16:00 GMT).
More Covid cases recorded in squads
Coronavirus looks set to have an impact on the Nations Cup on the pitch as well as off it.
Cameroon's Group A opponents Cape Verde have reported several cases at their pre-tournament training camp, with coach Bubista revealed to be among their latest positive tests.
Blue Sharks have six players - including two goalkeepers - isolating ahead of their match against Ethiopia on Sunday.
Senegal, runners-up in 2019, delayed their departure for the tournament after Saliou Ciss, Mamadou Loum and Habib Diallo tested positive, with other cases suspected.
Tunisia forward Seifeddine Jaziri and winger Youssef Msakni have also tested positive this week.
Jaziri was top scorer at the Fifa Arab Cup in Qatar in last month, scoring four goals as Tunisia reached the final where they lost 2-0 to Algeria while Msakni is set to appear at a seventh successive Nations Cup.