From the Document: "On June 22, President Trump issued a proclamation (amended on June 29) suspending the entry of foreign nationals (aliens) in certain nonimmigrant (temporary) visa categories that allow foreign nationals to work in the United States. Citing the high unemployment rate resulting from public health measures to reduce the spread of COVID-19 [coronavirus disease 2019], the proclamation suspends the entry of foreign nationals--and their accompanying family members--on H-1B, H-2B, J, and L visas, with some exceptions. [...] The proclamation suspending the entry of foreign nationals in certain nonimmigrant visa categories remains in effect from June 24, 2020, through December 31, 2020, with the possibility of continuation thereafter. Beginning 30 days after the effective date, and every 60 days thereafter, the Secretary of Homeland Security, in consultation with the Secretaries of Labor and State, may recommend changes to it."
CRS Insight, IN11435
Congressional Research Service: https://crsreports.congress.gov/