Public health and social measures (PHSM) against COVID-19 are non-specific countermeasures, previously referred to as non-pharmaceutical interventions, which have been implemented in many countries to control the pandemic. Whereas published studies report a strong overall epidemiological impact of lockdowns or PHSM in reducing cases (1–14), other studies suggest that lockdown itself may not be very effective if individual measures, such as wearing masks and restricting the use of restaurants and public facilities, are properly implemented (15, 16). Additional scientific evidence on the effectiveness of individual non-specific countermeasures is called for (e.g., school closures, bans on eating out and on large gatherings) (17–34). When the SARS-CoV-2 Alpha variant (B.1.1.7) with elevated transmissibility started to become widespread in Europe, strict lockdown measures were instated in European countries, which precluded an evaluation of each PHSM other than movement restriction of entire communities (35).

In Japan, PHSM have primarily comprised request-based nationwide cooperation in voluntarily reducing social contact and have not involved any legally binding penalties. The legal and administrative basis of such countermeasures is the state of emergency (SoE), which in Japan is declared based on the Act on Special Measures for Pandemic Influenza and New Infectious Diseases Preparedness and Response (2002) (36). In Japan, the first SoE was declared in April 2020 owing to a surge in cases during the first epidemic wave. Although the first SoE was lifted in May 2020, an SoE was declared twice, in January and April 2021, for municipalities in the Tokyo metropolitan area and the Kansai region owing to increasing pressure on health care services during the third and fourth epidemic waves. During the fourth wave, a larger number of people were infected with the Alpha variant (B.1.1.7), which has greater transmissibility than other previously circulating SARS-CoV-2 strains (37, 38). Because an SoE involves substantial adverse social and economic effects, pre-emergency measures (PEM) were devised as an alternative to an SoE. More customized countermeasures began from February 2021, and PEM were newly implemented based on the Revised Special Measures for Pandemic Influenza and New Infectious Diseases Preparedness and Response (2020), in the hopes of avoiding an SoE (39). In the PEM, the local governor of the target area can decide which sub-regional areas (e.g., cities, towns, and villages) will be subject to the countermeasures. PEM is a general term for interventions that do not involve restrictions on movement; instead, the countermeasures are more customized and focused on high-risk settings, including eating and drinking establishments that serve alcohol (40). That is, whereas SoE may be regarded as self-restrained contact reduction or a voluntary lockdown measure, PEM are more customized pre-lockdown policies that are expected to be implemented early in the epidemic and that represent more targeted intervention in high-risk settings only. Customized policies are in line with the scientific evidence that high-risk situations include drinking alcohol late at night and attending indoor gatherings, which sometimes trigger super-spreading events (41, 42).

During the fourth epidemic wave, an SoE and PEM were declared multiple times, targeting municipalities across Japan. However, the effectiveness of these countermeasures in controlling infections has yet to be evaluated, especially considering the spread of the highly transmissible Alpha variant (43). These countermeasures have been diverse. In areas of intervention, different series of countermeasures have been implemented, including a request for residents to refrain from unnecessary movement and restricting the use of public facilities. In particular, the content, intensity, and duration of PEM have not been uniform because local governments decide the details regarding countermeasures. Like an SoE, PEM are not legally binding. Thus, the effectiveness of these measures depends on the compliance of residents and employers in areas of intervention and how well contact can be avoided that could lead to infection. Objectively assessing the effectiveness of such countermeasures remains a scientific challenge.

With emergence of the Alpha variant, which led to a surge in COVID-19 cases close to the Christmas holiday season, many European countries immediately imposed strict lockdown policies and did not permit customized interventions to be implemented (44). In many prefectures of Japan, PEM with various customized interventions were implemented, which were subsequently followed by an SoE that enforced restrictions on free movement. The fourth wave involving the Alpha variant in Japan thus offers a unique opportunity to evaluate the effectiveness of such countermeasures. Considering that there may be additional opportunities to implement PHSM in the future (45), and complete reliance on pharmaceutical interventions and vaccination is not possible (46), it is vital to explicitly assess those interventions. Thus, in the present study, we aimed to estimate the effectiveness of PHSM in Japan.

In the present study, we evaluated the impact of the PEM and SoE on the epidemiological dynamics of COVID-19 from March to June 2021 in different regions of Japan, during which time the SARS-CoV-2 Alpha variant was predominant in the country. When PEM were implemented in 16 prefectures, the R_t was reduced to < 1 in only six of these prefectures, with the average relative reduction ranging from 2 to 19%. However, implementation of an SoE led to an average R_t value < 1 in 8 of the 10 prefectures where implemented, with an average relative reduction in the R_t ranging from 26 to 39%. For individual interventions, only school closures during periods of PEM implementation showed significant differences in reducing the R_t; no other interventions helped to explain variations in the relative reduction in R_t. Although there was no significant association between the relative reduction in R_t and the timing of initiating interventions, an extremely high positivity rate in PCR testing may predict a substantial reduction in the R_t. An increasing trend over time in the positivity rate for PCR testing results has been shown to predict a forthcoming epidemic wave (58). The present study findings further showed that PCR testing results that are extremely high, i.e., a very high positivity rate, may be one signature of a forthcoming reduction in the R_t, perhaps because a very high positivity rate is usually a sign of the need for strong intervention measures.

The findings of the present study revealed is that customized interventions (referred to as PEM in our study) in high-risk transmission settings may be insufficient to lower the R_t to < 1. Before the introduction of variant Alpha in Japan, a simple modeling study showed that R_t decreased to < 1 only after instating customized PHSM focused on high-risk settings. During the summer of 2020, interventions were centered on eating and drinking establishments operating at night and public facilities for mass gatherings and included shortening of opening hours, requests to not serve alcohol in Tokyo, restricting the number of people eating at the same table to four, and closure of nightlife areas in Osaka (59). Through that experience, such focused interventions were legally formalized by the Japanese government and categorized as PEM to help avoid unnecessary adverse social and economic impacts on the entire population. Unfortunately, with introduction of the more-transmissible Alpha variant, our findings showed that in many prefectures, the introduction of PEM alone was not sufficient to reduce the R_t value to below 1 during the spring of 2021. From July 2021, the SARS-CoV-2 Delta variant, which is even more transmissible than variant Alpha (60, 61), was introduced and rapidly became predominant among all virus strains circulating in Japan (62). Whereas elevated temperatures may help to slightly lower the R_t value (63), only stronger restrictions such as an SoE can suppress a sharp rise in COVID-19 infections (64, 65). Therefore, swift decisions regarding declaration of an SoE are required to bring an epidemic under control.

The PHSM explored in this present study are not accompanied by legal penalties In Japan; instead, both PEM and an SoE involve an official request from national and local governmental bodies to adhere to the policies (36). Furthermore, even without government intervention, people may precautionarily adopt risk-avoidance behavior, especially when the number of infected individuals is increased. Because the PEM and SoE were not legally binding in principle, we cannot explicitly determine whether people actually reduced their risky behaviors voluntarily (but actively) under the interventions (66). This characteristic complicates the evaluation in two ways. First, we may not always be able to anticipate whether public reactions and behavioral responses to PEM or an SoE will be the same as those observed from March to June 2021. If the general public has difficulty enduring restrictions on high-risk behaviors, the findings of the present study may not be applicable and cannot be expected in the future (67). In this sense, request-based (voluntary) restriction of social contact behaviors cannot be causally evaluated and the effectiveness of repeated implementation cannot be ensured. Second, psychological impacts could influence our outcomes. The declaration of an SoE itself might have had the effect of preventing risky behaviors, but such behavioral changes might have been induced primarily by elevated risk awareness, e.g., the declaration led to voluntary cancelation of travel and large gatherings or events (68). As such, it is vital to remember that the PEM and SoE in Japan rely on voluntary cooperation of the general public and employers, and people’s psychological responses to such requests have a key role in the effect of intervention. In these respects, it is inherently difficult to separate the effects of intervention from the effects of voluntary risk-avoidance behaviors. We performed additional analyses with the aim to strengthen our findings. As shown in Supplementary Table 3, we made a comparison of the R_t at 1 and 2 weeks prior to the implementation of PEM. Indeed, whereas the R_t decreased before the start of PEM in some prefectures and this decrease was large, the same trend was not observed in many prefectures. Supplementary Figure 3 depicts the change in Google mobility before and after intervention. Although in some prefectures, mobility had already decreased before the PEM, it was found that mobility generally decreased with the intervention. These supplementary analyses do not refute the effect of voluntary risk-avoidance behaviors. Rather, the important point here is that many prefectures were unable to reduce the R_t to below 1 with customized PEM that mostly targeted eating and drinking establishments whereas the SoE was able to flatten the epidemic curve.

It is worth mentioning that in a part of our analysis, we adopted a baseline period of the 7 days prior to the implementation of PHSM. Of course, risk awareness had been gradually increasing owing to the increasing epidemic size prior to the start of PHSM; therefore, people’s social contact behavior could have already begun to change during the 7-day baseline period. Thus, as part of the sensitivity analysis, the duration of the baseline period was altered. Comparing the R_t 7 days prior to the intervention and during the entire intervention period, PEM and the SoE reduced the R_t by an average of 11.3% and 27.6%, respectively. When the baseline was set to 14 days, the PEM and SoE decreased the R_t by an average of 19.4% and 38.7%, respectively. However, this analysis did not substantially alter our findings.

Our results regarding school closures during PEM were consistent with those of published studies (69–74). School closures during an SoE did not lead to a marked reduction in R_t; therefore, school closures would not be consistently effective across all possible epidemiological conditions (74, 75).

Caution is needed when discussing the timing of PHSM implementation (74). The short-term goals of PHSM may include to (i) suppress an epidemic, (ii) ease caseload pressure on health care facilities, and (iii) buy time to increase protection via pharmaceutical interventions (e.g., vaccination). If goal (iii) is not critical, early implementation of PHSM will always be the most effective owing to the containment of an epidemic at a local level. This is particularly true for PEM; the risk of an epidemic wave could have been greatly reduced if PEM had been implemented before a substantial increase in the COVID-19 incidence and if the PEM covered the areas or regions with increasing virus transmission. It must be remembered that the estimated relative reduction in R_t found in the present study is conditional on implementation at a given timing; in general, the effectiveness of PHSM is greater if implemented earlier (76, 77).

Certain limitations in this study must be acknowledged. First, the quantified risk reduction would not be causal, as mentioned above; thus, similar impacts of PHSM are not guaranteed (40). Second, our analysis relied on the change in R_t before and after intervention. We argued that this change may be attributable to extrinsic effects, namely, PHSM. However, other extrinsic factors (e.g., behavioral changes) and intrinsic factors (e.g., depletion of susceptibles) can also lead to a reduction in the R_t value. In fact, there were continual government announcements with respect to the ongoing risk of infection and requests to wear a face mask, maintain an appropriate social distance, and engage in preventive measures (76). Third, in our analysis, we did not evaluate the time-dependent variations in intervention effectiveness. During the later stages of PHSM, the degree of preventive effectiveness can sometimes be magnified, perhaps owing to a gradual reduction in high-risk contacts. Fourth, we used the prefecture as the unit in our analysis, and these were analyzed independently. Spatial correlations associated with travel across prefectures could not be controlled (40).

Although not causal, the present study provides important evidence indicating that achieving a substantial reduction in R_t in the presence of a highly transmissible SARS-CoV-2 variant requires implementation of an SoE. Continued epidemiological assessment of PHSM is critical, alongside further analysis of the heterogeneities in effectiveness among interventions.

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.

This study was approved by the Medical Ethics Board of the Graduate School of Medicine at Kyoto University (R2676).

KH conceived the study. KH and HN conceptualized the study design and drafted early versions of the manuscript and figures. KH, AA, MF, AS, TK, and MS collected the data. KH, NL, AA, MF, AS, and TK performed the statistical analyses. All authors provided comments on the manuscript and approved the final version of the manuscript.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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