Stay-at-home order in the context of "Quarantine"

During the early stages of the COVID-19 pandemic, a number of non-pharmaceutical interventions, particularly lockdowns (encompassing stay-at-home orders, curfews, quarantines, cordons sanitaires and similar societal restrictions), were implemented in numerous countries and territories around the world. By April 2020, about half of the world's population was under some form of lockdown, with more than 3.9 billion people in more than 90 countries or territories having been asked or ordered to stay at home by their governments.

In addition to the health effects of lockdown restrictions, researchers had found the lockdowns may have reduced crime and violence by armed non-state actors, such as the Islamic State, and other terrorist groups. In addition, lockdowns had increased the uptake of telecommuting, reduced airborne pollution, and increased adoption of digital payment systems.

On 23 January 2020, the Chinese Communist Party (CCP) and the State Council of China imposed a lockdown in Wuhan and other cities in Hubei in an effort to quarantine the center of an outbreak of COVID-19; this action was commonly referred to as the Wuhan lockdown (Chinese: 武汉封城; pinyin: Wǔhàn fēng chéng). The World Health Organization (WHO), although stating that it was beyond its own guidelines, commended the move, calling it "unprecedented in public health history". CCP general secretary Xi Jinping said he personally authorized the unprecedented lockdown of Wuhan and other cities beginning on 23 January.

The lockdown in Wuhan set the precedent for similar measures in other Chinese cities. Within hours of the Wuhan lockdown, travel restrictions were also imposed on the nearby cities of Huanggang and Ezhou, and were eventually imposed on all 15 other cities in Hubei, affecting a total of about 57 million people. On 2 February 2020, Wenzhou, Zhejiang, implemented a seven-day lockdown in which only one person per household was allowed to exit once each two days, and most of the highway exits were closed. On 13 March 2020, Huangshi and Qianjiang became the first Hubei cities to remove strict travel restrictions within part or all of their administrative confines. On 8 April 2020, the Wuhan lockdown officially ended. The lockdown, combined with other public health measures in early 2020, succeeded in suppressing virus transmission and averted a more widespread outbreak in China.

The COVID-19 pandemic in California began earlier than in some other parts of the United States. Ten of the first 20 confirmed COVID-19 infections in the United States were detected in California, and the first infection was confirmed on January 26, 2020. All of the early confirmed cases were persons who had recently travelled to China, as testing was restricted to this group, but there were some other people infected by that point. A state of emergency was declared in the state on March 4, 2020. A mandatory statewide stay-at-home order was issued on March 19, 2020; it was ended on January 25, 2021. On April 6, 2021, the state announced plans to fully reopen the economy by June 15, 2021.

As of June 16, 2022, the California Department of Public Health (CDPH) has reported 9,199,942 confirmed cumulative cases and 91,240 deaths in the state. This was the highest number of confirmed cases in the United States, but because the state has the highest population of any US state, it also had one of the lowest rankings (41st highest out of 50 states) for confirmed cases per capita. It has the highest count of deaths related to the virus, but a relatively low (35th highest) count of deaths per capita. As of June 15, 2021, California had administered 40,669,793 COVID-19 vaccine doses, the largest number of doses nationwide, and was one of the highest ranked (11th out of 50 states) in terms of per-capita dose administration.