In August 2020, as the Democratic party officially nominated former U.S. Vice President Joe Biden as their 2020 presidential candidate and Sen. Kamala Harris of California as their pick for Vice President in virtual proceedings amidst the COVID-19 pandemic, a collage of images was circulated online that supposedly showed the duo in a crowd without face masks:
These are genuine photographs of Biden and Harris; however, they were not taken in August 2020. They were snapped before cities in the United States implemented regulations, such as the use of face masks and limits on crowd sizes, to combat the spread of the COVID-19 coronavirus disease.
These images come from a campaign rally held on March 9, 2020, in Detroit, Michigan. At the time, the Democratic field was thinning out, and Biden's former competitors, such as Harris and New Jersey Sen. Cory Booker, were offering their endorsements of the former vice president:
https://www.youtube.com/watch?v=T7FcOjczZL8
Although the initial cases of COVID-19 had already been found in the United States at that time, the first lockdowns weren't implemented in states until a few weeks after this event. California was the first state to order a COVID-19 related lockdown on March 19, and in Michigan, where this rally was held, lockdowns weren't ordered until March 24.
At the national level, it wasn't until early April that the Centers for Disease Control and Prevention (CDC) issued guidelines recommending the use of face masks in public to slow the spread of COVID-19.
In other words, these images truly show Biden and Harris in a large crowd, not wearing masks. However, the photographs were taken weeks before face masks and other social distancing guidelines were first implemented in the United States.