The world is more than eight months into the COVID-19 pandemic and still little is known about the novel coronavirus. With no vaccine or treatment or even full understanding of the way the virus is transmitted, social distancing has consistently been promoted — from the beginning — as the best available way to prevent further spread of the virus.

By now, most people are likely accustomed to keeping at least 6 feet apart, though perhaps other measures such as keeping the kids at home from school, not going to public events, and working from home are more difficult to get used to. Still, researchers from Massachusetts General Hospital have published a study showing that following social distancing guidelines is indeed an effective way to slow the spread.

According to the study, social distancing reduced the total number of COVID-19 cases by about 1,600 nationwide just a week after officials began implementing social distancing guidelines. Two weeks later, social distancing reduced the number of cases by about 55,000, and three weeks later by more than 620,000 cases.

24/7 Wall St. reviewed nationwide data from the study published in PLOS Medicine, a peer-reviewed weekly medical journal, to gauge the efficacy of social distancing measures.

Click here for each state’s outbreak before and after social distancing
Click here for our detailed methodology

The researchers caution that it is impossible to know exactly which social distancing measures — closing schools, capping gatherings, shutting down nonessential businesses, or issuing stay-at-home orders — worked the best as many states began closing around the same time in mid-March and some of the measures were used simultaneously.

Before any forms of social distancing were in place, the number of new COVID-19 cases in a state was doubling every 3.3 days on average. After three weeks of social distancing, the time it took for new cases to double slowed to 7.9 days on average.

In some states, the time it took for the number of total COVID-19 cases to double increased significantly in the three weeks since the first statewide social distancing measure was issued. In Washington state, for example, the doubling frequency went up from six days two weeks after implementation and to 46 days three weeks after implementation. A similarly big difference was noticed in seven more states.

On the other hand, the doubling frequency actually decreased in five states. This may be due to the fact that some states started to relax government-issued social distancing measures less than four weeks after mandating them, according to the study.

As of Aug. 27, nearly 5.9 million coronavirus cases have been reported across the U.S. since late January. While the spread of COVID-19 has begun to slow down after a resurgence in many states in June and July, daily new cases are still increasing in major metropolitan areas — here are the cities where the coronavirus is growing the fastest.