< PREVIOUS SLIDE SLIDE 1 of 22 NEXT SLIDE > Maria D Van Kerkhove, World Health Organization (WHO) Head AI Emerging Diseases and Zoonoses Units, speaks during a press conference following an emergency committee over the new SARS-like virus spreading in China and other nations, in Geneva on January 22, 2020. © Provided by CNBC

World Health Organization officials said not all people who recover from the coronavirus have the antibodies to fight a second infection, raising questions as to whether or not patients develop immunity after surviving Covid-19.

“With regards to recovery and then re-infection, I believe we do not have the answers to that. That is an unknown,” Dr. Mike Ryan, executive director of WHO’s emergencies programs, said at a press conference at the organization’s Geneva headquarters on Monday.



A preliminary study of patients in Shanghai found that some patients had “no detectable antibody response” while others had a very high response, said Dr. Maria Van Kerkhove, WHO’s lead scientist on Covid-19. Whether the patients that had a strong antibody response were immune to a second infection is “a separate question,” she added.

More than 300,000 of the 1.87 million coronavirus cases across the world have recovered, WHO officials noted, adding that they need more data from recovered patients to understand their antibody response, whether that gives them immunity and for how long.

“That’s something that we really need to better understand is what does that antibody response look like in terms of immunity,” Van Kerkhove said.

Ryan said there are questions about whether the virus can reactivate after a patient recovers and tests negative for Covid-19.

“There are many reasons why we might see reactivation of infection either with the same infection or another infectious agent,” he said. In general, “there are many situations in viral infection where someone doesn’t clear the virus entirely from there system.” Some patients can also clear the main infection but develop a secondary bacterial infection, he said.

Related slideshow: Coronavirus (COVID-19) outbreak around the world (Provided by Photo Services)