French researchers caution that reopening too quickly — without a vaccine or herd immunity — greatly heightens the risk of a second coronavirus wave.
(CN) — As Covid-19 spreads around the world, so does the implementation of lockdowns to slow the infectious disease, plunging the global economy into darkness. Now, the common suggestion is to slowly dim the lights as countries around the world struggle to find a balance between resuming economic activity amidst the pandemic.
In analyzing the impact of lockdown measures in France, researchers cautioned in Frontiers in Medicine on Thursday that reopening too quickly can lead to a second wave of the infectious virus.
“The lockdown was effective at reducing the transmission rate of Covid-19 but the potential for a second wave of infections is extremely high,” said Dr. Lionel Roques, one of the study’s authors, in a statement.
“Herd immunity is far from reached and many infectious cases still exist,” Roques warned.
The novel coronavirus SARS-Cov-2 that causes the respiratory disease Covid-19 originated in the Wuhan province of China last December and was first detected in France on Jan. 24. French President Emmanuel Macron called for a lockdown March 17 to slow the spread of the highly infectious disease.
France’s lockdown, which lasted nearly two months, kept citizens confined to their homes except for grocery shopping, one hour of exercise, or essential work. Schools and non-essential businesses closed as well.
In hopes of quantifying the effectiveness of the lockdowns, researchers at the Institut National de la Recherche Agronomique in France and the Medicentre Moutier in Switzerland fed data collected between March 31 to April 15 into models to estimate the rate of disease spread and infection-fatality-ratio.
A single infectious case spreads on average to 3.28 more people. When that effective reproduction number drops below one, a virus typically dies out since it is unable to infect more hosts.
When France began easing its lockdown on May 11, researchers estimate only 3.7% of the population had contracted Covid-19. The risk of contracting the disease diminishes only with the development of a vaccine or when a population reaches herd immunity on its own.
Herd immunity occurs when 69 to 80% of the population has been infected, researchers estimate.
They cautioned that “a too fast relaxation of the lockdown-related restrictions before herd immunity is reached or efﬁcient prophylaxis is developed, would expose the population to an uncontrolled second wave of infection.”
To date, the country has confirmed 152,000 cases of Covid-19 and 29,021 deaths. According to the French government, 69,455 people have recovered.
While daily reports of new cases over the past week ranged from 352 to 3,325, the country averaged 956 new cases each day.
Although some people become restless with the restrictions, research suggests the lockdowns work.
Throughout the stay-at-home-order, France’s infection fatality rate dropped to .8%. Researchers further estimated that the policies helped reduce the effective reproduction number for Covid-19 down to one-seventh of pre-lockdown spread, indicating “that the restriction policies were very efﬁcient in decreasing the contact rate and therefore the number of infectious cases.”
“The virus was spreading so fast that the second battle, that of the containment of the epidemic, was lost and so lockdown was initiated. Our calculations suggest the restrictions were very efficient at slowing the transmission of Covid-19, with a 7-fold reduction in the R-number to 0.47,” Roque added. The R-number refers to the effective reproduction, or roughly how many people a single person can pass the virus on to.
Whether they are ready or not, France continued to lift travel restrictions Monday and allowed bars, museums, and theaters to reopen in certain areas.