Catching the coronavirus disease once may not protect you from getting it again, according to the World Health Organisation ( WHO ), a finding that could jeopardise efforts to allow people to return to work after recovering from the virus. “There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection,” the United Nations agency said in an April 24 statement. The WHO guidance came after some governments suggested that people who have antibodies to the coronavirus could be issued an “immunity passport” or “risk-free certificate” that would allow them to travel or return to work, based on the assumption that they were safe from reinfection, according to the statement. People issued such a certificate could ignore public-health guidance, increasing the risk of the disease spreading further. Chile was the first country to announce plans to issue immunity cards based partly on antibody tests. This has raised concerns because the tests have proven unreliable elsewhere, and some people may get deliberately ill to obtain the card. The United States and others have nonetheless said they are looking into the option. While there is a consensus that the key to ending the coronavirus pandemic is establishing so-called herd immunity, there are many unknowns. South Korean patients with reactivated virus have ‘little or no infectivity’ One is whether researchers can develop a safe and effective vaccine. Another is how long people who have recovered have immunity; reinfection after months or years is common with other human coronaviruses. Finally, it is not clear what percentage of people must be immune to protect the “herd”. That depends on the contagiousness of the virus. The WHO said it was still reviewing the scientific evidence on antibody responses to coronavirus, but as yet no study has evaluated whether the presence of antibodies “confers immunity to subsequent infection by this virus in humans”. And while many countries are currently testing for antibodies, these studies are not designed to determine whether people recovered from the disease acquire immunity, the agency said. As the number of infections worldwide reached some 2.8 million and the death toll crossed 195,000, the WHO has joined with global leaders to speed up the development and production of vaccines and therapeutics that can stamp out the coronavirus pandemic , and to ensure they distributed quickly and equitably across the globe. “Past experience has taught us that even when tools are available, they have not been available equally to all,” Tedros Adhanom Ghebreyesus, WHO director general said during a virtual meeting to launch the international initiative . “We cannot allow that to happen.” Coronavirus models made governments take action, but how useful are they really? The new programme, called Access to Covid-19 Tools Accelerator, or the ACT Accelerator, is a collaboration between the WHO and dozens of governments, non-profit organisations and industry leaders. Friday’s launch event was co-hosted by French President Emmanuel Macron, European Commission President Ursula von der Leyen and philanthropists Bill and Melinda Gates. Leaders from South Africa, Rwanda, Germany, Great Britain, Spain, Italy, Malaysia, Saudi Arabia, Finland and Costa Rica joined the call to pledge their commitment to work with and support the ACT Accelerator.