**2. The Effect of Government Response on the Infection Rate**

*2.1. Immediate Effects of Government Response on the Infection Rate*

Studies have shown that social interventions are needed to control the spread of epidemic diseases. Bauch and Galvani point out thatcontrol of the SARS coronavirus depended partly on the degree of acceptance of quarantine and isolation among the population; such acceptance is often determined by social norms [12]. In the book *The Rules of Contagion: Why Things Spread and Why They Stop*, Kucharski concluded that the factors that influence the reproduction number of an epidemic disease include duration, opportunities, transmission, and susceptibility [13]. In his view, curing a patient reduces the duration of infection, isolating a patient reduces the opportunities for infection, wearing a condom or mask reduces contagion, and vaccination reduces population susceptibility. Government response to COVID-19 consists of social interventions implemented to curb the spread of the disease. COVID-19 intervention policies are complex and vary between countries, but they can be broadly categorised into five major areas, namely, containment and closure, economic responses, health systems, vaccine policies, and miscellaneous policies [3]. Many studies have attempted to determine the most effective intervention policies. For example, Richard et al. examined the effects of four types of government response—event bans, school closures, bar and pub closures, and lockdown—and discovered that event bans and school closures directly reduced virus transmission, while the influence of a full lockdown was slightly delayed [14]. Scholars have used epidemiological data on COVID-19 and anonymised migration data to simulate outbreaks and intervention effects across China. A comparison of infections in Wuhan, Hubei province, with those in other cities in Hubei and cities in other provinces revealed that early detection and isolation were more effective than travel restrictions. Reducing social contact curbed the spread of COVID-19 and prevented or delayed the arrival of a second wave of the outbreak. The authors also found that although travel restrictions had not prevented the virus from spreading from Wuhan, they had prevented its wider geographical spread [4].

The degree of policy implementation is also an important predictor of the COVID-19 infection rate. An international comparative study using data from China, Italy, Brazil, Canada, the United Kingdom, and the United States found that the stringency of intervention policy implementation was negatively associated with the number of new cases. This study also found that the Chinese government had maintained strong prevention and control measures for the first 100 days of the outbreak, during which China had experienced a dramatic decrease in infections [3]. When the virus was first detected in Guangdong province, the province's health commission quickly activated a Level I emergency response and implemented a series of public interventions, including traffic restrictions, social distancing, home and centralised quarantines, medical resource mobilisation, and other prevention and control measures, which significantly restrained the local spread of the disease [15]. Differences in the degree of policy implementation may stem from differing individual responses to government policies or from differences in national policy environments, such as social norms, cultural traditions, the political atmosphere, and other macro-level factors that interact with government response [16,17]. In general, policies that are strictly enforced tend to bring about better results, especially in the early stages [3,4,6,14–16].

The timing of policy initiation is another important predictor of the effectiveness of government response to COVID-19. Take social distancing as an example. A series of studies found that isolating infected people decreased and delayed transmission as well as reducing the epidemic's peak [4,8,18–20]. Using counterfactual simulations, another study discovered that if the same restrictions on mobility had been implemented just one to two weeks earlier, a substantial number of cases and deaths would have been avoided. Specifically, 61.6% of the infections and 55% of the deaths reported nationwide by May 3, 2020 could have been avoided if these preventive and control measures had been implemented just one week earlier [4]. A study of the relationship between the first emergency quarantine policy in Portugal from 18 March to 2 May 2020 and the public's health behaviour showed that 79.8% of the participants, whose physical activity took place indoors, complied with the government quarantine measures and adapted their health behaviour [21]. Therefore, early social distancing plays a key role in relieving pressure on healthcare facilities and ensuring a sustained supply of healthcare resources. At this level, the timing of social distancing implementation is crucial to controlling large-scale outbreaks. Social distancing has been shown to reduce not only new cases but also cumulative cases. This implies that early government intervention may have some sustained effects, in that people became more aware of the virus during home isolation and were more likely to adopt protective action recommendations (PARs) after home isolation, thereby reducing their own infection rates.
