Lockdowns Must Last At Least 60 Days

A new modeling study simulates responses to the pandemic in an attempt to find the best one

New York City, the center of the U.S. epidemic, went into lockdown on March 22, and it became one of the last places in the country to ease its restrictions on June 8. Altogether, lockdown in New York City lasted for about 78 days, or just over 11 weeks. And while this may have seemed like an eternity, new research in Nature Human Biology reaffirms that a long lockdown is necessary to keep the Covid-19 pandemic in check.

In the new paper, published Monday, researchers from the Barcelona Institute for Global Health report the findings of a modeling study in which they simulated different responses to the pandemic in an attempt to find the best possible one. The model took into account several factors, including human behavior, the potential for immunity, and the length of lockdowns, which allowed the authors to determine the optimal length for a lockdown and the best way to reopen safely.

Lockdowns, they found, “should remain in place for at least 60 days to prevent epidemic growth, as well as a potentially larger second wave of SARS-CoV-2 cases occurring within months.”

Reopening, they found, must happen gradually. Acknowledging that a country must balance public health with the health of its economy, they show that a gradual reopening strategy is always safer than one that happens abruptly.

As the United States continues to reopen, more than half the states are experiencing spikes in new Covid-19 cases. Public health officials warned that the country was not ready to reopen, while the White House downplayed — and continues to minimize — the threat of the pandemic.

The new model also takes into account other factors that could mitigate the risk of Covid-19 spread, including social distancing, human behavior, risk perception and awareness, and the potential for immunity. Notably, all of these factors can change over time. For example, as the authors posit, people may be more aware and vigilant at the beginning of an outbreak than at the end of it because their awareness of the situation likely relaxes over time.

Two factors emerged as especially important in controlling an ongoing wave of cases and preventing a new one: how long immunity lasts, and human behavior. The study showed that if immunity lasts for a year as opposed to four months, the time between waves of cases could double. That, unfortunately, remains out of our control. Our behavior, however, isn’t: Now, just as at the beginning of the pandemic, scientists stress that masks, hand hygiene, and social distancing are crucial for curbing Covid-19’s spread.