This is not an absolute right. There are exceptions, due to extraordinary public health emergencies: https://www.cdc.gov/quarantine/aboutlawsregulationsquarantineisolation.html. Quarantine/isolation orders ("lockdowns" if you will) preclude peaceably assembling.Constitution of United States of America 1789 (rev. 1992)
"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances."
"The federal government derives its authority for isolation and quarantine from the Commerce Clause of the U.S. Constitution [emphasis added]. Under section 361 of the Public Health Service Act (42 U.S. Code § 264), the U.S. Secretary of Health and Human Services is authorized to take measures to prevent the entry and spread of communicable diseases from foreign countries into the United States and between states. The authority for carrying out these functions on a daily basis has been delegated to the Centers for Disease Control and Prevention (CDC)."
"States have police power functions to protect the health, safety, and welfare of persons within their borders. To control the spread of disease within their borders, states have laws to enforce the use of isolation and quarantine. These laws can vary from state to state and can be specific or broad. In some states, local health authorities implement state law. In most states, breaking a quarantine order is a criminal misdemeanor. Tribes also have police power authority to take actions that promote the health, safety, and welfare of their own tribal members. Tribal health authorities may enforce their own isolation and quarantine laws within tribal lands, if such laws exist."