All countries have reacted to the Covid-19 pandemic with policies aiming to contain the spread of the virus within their territory. Most countries have done so by severely limiting basic freedoms of their inhabitants. The English word “lockdown” has been used in many languages to refer to very different types of locally unprecedented policies. At the end of 2019, the definition of “lockdown” on Wikipedia read: “an emergency protocol that usually prevents people or information from leaving an area”. At that time, there was no reference to epidemiological measures. By February 2022, Wikipedia’s definition reads “A Lockdown is a restriction policy for people or community to stay where they are, usually due to specific risks to themselves or to others if they can move and interact freely. The term “stay-at-home” or “shelter-in-place” is often used for lockdowns that affect an area, rather than specific locations.” However, the actual use of the word “lockdown” is enormously different in different countries. In the first weeks of the pandemic, the policies implemented in Wuhan were referred to as lockdowns in the international media, so the term implicitly implied strict, all-day stay-at-home orders. But that changed after most governments in the world implemented policies that either themselves or the international media referred to as “lockdown”. For many, the word has become synonymous with any extraordinary policies imposed in connection with the Covid-19 pandemic. For instance, the closure of schools and businesses was referred to as a lockdown in several European countries, even when people were allowed to circulate freely.

The word quarantine is used in many countries to refer to local, or even national stay-at-home orders. Thus the word quarantine can locally be used interchangeably with the word lockdown, but it is generally defined differently. Yet it is commonly defined more narrowly. In Wikipedia it says: “A quarantine is a restriction on the movement of people, animals and goods which is intended to prevent the spread of disease or pests. It is often used in connection to disease and illness, preventing the movement of those who may have been exposed to a communicable disease, yet do not have a confirmed medical diagnosis.” The crucial difference is that a quarantine only affects “those who may have been exposed” to the disease. Of course, everyone “may have been exposed” in theory, but usually being quarantined requires a certain likelihood of exposure. People can be quarantined because they were in close contact with an infected person, for instance. However, governments also decided to quarantine travellers, often in cases where the incidence in the departure country is not significantly higher than the incidence in the arrival country. In fact, even individuals travelling from a “high incidence” country are very unlikely to be infectious themselves. When a person travels from a country with a 7-day incidence of 500 new infections per 100,000 inhabitants, this means that an individual’s risk of having recently contracted the virus is 0.5% – assuming an even distribution of the virus through the entire population. Of course, the likelihood is much lower if this person has no symptoms or has even tested negatively. In many countries, travellers are nevertheless treated the same as e.g. the spouse or close co-worker of an infected person: They are forced to stay home for a period of between 5 and 14 days, which sometimes can be evaded or shortened by testing negatively or by being vaccinated. A quarantine is mostly even stricter than a general lockdown. While people under a lockdown are normally allowed to leave their house for a set of reasons such as work or essential shopping, quarantined individuals are not allowed to leave their house under any circumstances (except emergencies). If a person was tested positive or shows symptoms, separating this person from non-infected people is usually called isolation but is also often referred to as quarantine.

Because the word lockdown is used universally for all sorts of pandemic policies, I will mostly stick to the less ambiguous terms stay-at-home order or stay-at-home restrictions in this project. A stay-at-home order, according to Wikipedia, “is an order from a government authority that restricts movements of a population as a mass quarantine strategy for suppressing or mitigating an epidemic or pandemic by ordering residents to stay home except for essential tasks or for work in essential businesses”. Stay-at-home orders are mandatory regulations that prevent citizens either from leaving their homes or from entering public space. A common type of stay-at-home restrictions is a curfew, which restricts people’s movement to certain hours. Usually, a curfew bans leaving the house during the night. Unlike for quarantine, stay-at-home orders and curfews usually allow people to go out if they had a good reason. The exact term differed, for instance, UK citizens needed a “reasonable excuse” to go out. In all countries, “essential work” justified leaving the house, although there have been huge differences in which work was deemed essential and whether remote work was mandatory where possible. Urgent medical visits and health emergencies were other reasons that were accepted everywhere. Essential shopping was allowed everywhere too, but often only in very limited time frames. This included supermarkets, pharmacies, gas stations, bank services, and often different other shops that were seen as important. Walking a dog was regarded as a good reason to leave the house in most places, often limited to a very short time. A large difference between stay-at-home orders in different countries was whether physical activity was treated as a good reason to leave the house. In some places, this was not the case, in others, physical exercise was allowed limited to a certain time or only in close proximity to home. Other countries allowed going for a walk without time constraints.

In the scientific literature, all these policies and countless other “lockdown policies” are often referred to as non-pharmaceutical interventions (NPI). When Covid-19 was a new disease, there existed only NPI while now there are different pharmaceutical interventions, too. Note that while vaccination itself is a pharmaceutical intervention, vaccine mandates and restrictions such as banning unvaccinated people from certain places are NPI.

In this project, I focus on stay-at-home orders and curfews. I will also include policies that impose conditions for leaving the house, e.g. the obligation to wear a mask outside independent of the distance towards others.