Spanish GP boss Ramon Tremosa says he isn't sure if Barcelona will be able to welcome spectators to the Barcelona race in May.
"We don't know yet," he is quoted by El Mundo Deportivo newspaper.
"There may be 20,000, 50,000, 100,000 or none. A lot will depend on the vaccine and the effectiveness of rapid tests.
"If we have a fourth wave in Easter it will be difficult, but if the incidence decreases as expected, the situation must be allowed to normalise."
Tremosa said the cancellation of pre-season testing in Barcelona is just "one more impact of the pandemic". The single 3-day test is moving to Bahrain.
Red Bull official Dr Helmut Marko is also hopeful the covid situation will begin to improve in 2021.
"I hope that we can have more races with spectators through the measures such as vaccination and the bubbles of the individual teams," he told RTL.
The Austrian said he is expecting F1 to implement "an indirect vaccination requirement".
"The beginning of the season will be bumpy, but Monte Carlo has already announced that the race will take place with a reduced number of spectators," Marko added.
