(CNN) You can catch it more than once.

The World Health Organization has warned against the idea that coronavirus immunity passports can provide a safe way out of lockdown.

Many countries were hoping to start issuing risk-free certificates to people who have had the disease, allowing them to return to work , travel and go about their business. The plan was based on the assumption that Covid-19 survivors develop immunity.

But yesterday the WHO said no evidence exists that people who have recovered from the disease and developed antibodies are protected from catching it again.

The organization went further, warning that the use of immunity passports could lead to a spike in new infections. That's because people who assume they are immune are more likely to ignore public health advice.

In the wake of the WHO's alert, it becomes apparent that global efforts must focus on the only other way to gain protection: a vaccine

YOU ASKED. WE ANSWERED

Q: What do ventilators do, and how do they help treat patients?

A: A ventilator forces air into the lungs of a patient who cannot breathe on their own because of severe pneumonia or acute respiratory distress syndrome. Such machines are often used by doctors treating the most severe cases of Covid-19, and requires them to place a tube down their patient's throat, a procedure known as intubation. It's often a deteriorating patient's last best hope to recover, but data so far shows the prognosis isn't good. A study of New York's largest health system showed that about a quarter of A ventilator forces air into the lungs of a patient who cannot breathe on their own because of severe pneumonia or acute respiratory distress syndrome. Such machines are often used by doctors treating the most severe cases of Covid-19, and requires them to place a tube down their patient's throat, a procedure known as intubation. It's often a deteriorating patient's last best hope to recover, but data so far shows the prognosis isn't good. A study of New York's largest health system showed that about a quarter of coronavirus patients who needed ventilators to help them breathe died within the first few weeks of treatment.

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WHAT'S IMPORTANT TODAY

More grim milestones

The coronavirus has now killed more than 200,000 people globally , according to Johns Hopkins University.

But official statistics are only capturing confirmed cases. With most countries struggling to test everyone who shows symptoms, the number of Covid-19-related deaths is likely much higher. These people might have died at home, in nursing homes , or in hospitals where testing was unavailable.

The United Kingdom yesterday became the fifth country in the world to record more than 20,000 deaths, after Italy, the United States, Spain and France. Just weeks ago, the UK government's chief scientific adviser, Patrick Vallance, said that limiting deaths to around 20,000 would be a "good outcome."

The US, meanwhile, is nearing 1 million cases . More than 53,600 Americans have died so far, with New York state alone recording more than 22,000 coronavirus deaths.

Trump calls time on briefings

President Donald Trump did not hold a daily coronavirus update yesterday, tweeting that briefings are "not worth the time & effort." The media, he added, asks "nothing but hostile questions" and "then refuses to report the truth or facts accurately."

Trump's tweets came after he was widely criticized last week by health experts for his dangerous suggestion that research should be done into whether disinfectants can serve as a potential coronavirus treatment. On Friday, amid the outcry, Trump staged a short briefing and did not allow questions from the media

The decision to skip Saturday's briefing comes after CNN reported Friday that there has been a concerted effort among aides and allies to stop Trump conducting the daily coronavirus briefings.

A senior administration official, meanwhile, said discussions are under way to replace Health and Human Services Secretary Alex Azar following criticism of the early federal response to the epidemic.

Coronavirus exposes deep divisions everywhere

The pandemic has had very different consequences for the rich and the less well-off.

In France, billionaires have isolated themselves at luxurious hideaways on the Mediterranean, while residents in more disadvantaged and crowded areas of France are facing a surge in deaths, along with unrest on the streets

People living in Hong Kong's "cage homes" -- subdivided apartments that often have space for only a bed and some clothes -- find it impossible to self-isolate and stay safe.

In the US, hundreds of thousands of people have joined the gig or underground economies after unexpectedly losing their jobs. People of color, women and teens have been particularly hard hit.

Boris Johnson returns

The British Prime Minister is due to return to work on Monday, his office said, exactly a month after announcing he tested positive for Covid-19. Johnson was hospitalized and spent several days in an intensive care unit before being released two weeks ago

African Americans urged to defy governors' efforts to reopen businesses

A coalition of civil rights and black religious leaders is urging African American residents who live in states that are moving swiftly to reopen their economies to stay home in defiance of directives until there's evidence the coronavirus outbreak has eased.

Georgia was among the first states to begin reopening nonessential businesses on Friday. A third of the state's residents are African American, a community that is disproportionately dying from Covid-19 . Figures from the Centers for Disease Control and Prevention show black patients make up nearly 20% of US coronavirus deaths, although African Americans represent only about 13% of the nation's population.

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TODAY'S TOP TIPS

Talking about coronavirus is hard enough when you're an adult. For kids, the pandemic is both scary and incomprehensible.

CNN partnered with "Sesame Street" for a special town hall about coronavirus to give children the opportunity to learn more about the pandemic. Elmo asked why people wear masks if it's not Halloween, while Big Bird wondered if Covid-19 was just a bunch of letters and numbers.

And CNN Chief Medical Correspondent Dr. Sanjay Gupta made an impromptu model of the virus using a ball and a crown.