In an effort to understand how many people have been infected with the new coronavirus, the World Health Organization (WHO) is planning a coordinated study to test blood samples for the presence of antibodies to the virus. Called Solidarity II, the program, which will involve more than half a dozen countries around the globe, will launch in the coming days, says Maria Van Kerkhove, who is helping coordinate WHO's COVID-19 response.
Knowing the true number of cases—including mild ones—will help pin down the prevalence and mortality rate of COVID-19 in different age groups. It will also help policymakers decide how long shutdowns and quarantines should last. "These are answers we need, and we need the right answers to drive policy," WHO's executive director for health emergencies, Michael Ryan, told a press briefing on 27 March.
Tests that detect the virus directly have already identified nearly 1 million cases of COVID-19 around the world. But because of test shortages, many cases, especially mild ones, have been missed. Antibody tests can help give a better sense of the virus' true spread because they can also detect whether a person has been infected in the past, leaving them with antibodies that might protect against future infection.
Companies and labs around the world have been racing to produce tests for COVID-19 antibodies in people's blood. Specialist labs have accurate ways to measure antibodies, but commercial tests aren't yet widely available, and their accuracy is still being evaluated, including by WHO.
Solidarity II is the final part of a "three-pronged approach" to gathering as much data on antibodies as quickly as possible, Van Kerkhove says. First, WHO is working with researchers in a number of countries that have had significant outbreaks to gather clues about how many people have antibodies to the virus, she says. Those studies "are absolutely critical for our understanding of the epidemiology of COVID-19," she says, but they have each used slightly different methods. Second, WHO has published several standard protocols for "early investigations," including antibody studies, so that different countries and teams can combine their data to draw more significant conclusions. The agency is helping countries and research teams adapt the protocols to their local conditions, collect ethical approvals, and carry out the test assays, she says.
Solidarity II goes a step further. It will give participating countries a chance to pool findings from large-scale antibody studies that should fill out the global picture quickly. That's also the idea behind the first Solidarity, a megatrial of possible COVID-19 treatments that WHO launched last month. (A Solidarity III trial is also in the works, Ryan said at the briefing. It will test possible drugs that health care workers and others at high risk for contracting the virus could take to protect them from getting sick.) Initial results from Solidarity II could be available within a few months, Van Kerkhove says, though the study is intended to run for 1 year or longer.
Several smaller antibody surveys now getting underway could yield early results within weeks. For instance, Jay Bhattacharya, a health policy expert at Stanford University, says next week he and his colleagues hope to test 5000 people in California's Santa Clara county for antibodies. He says the study is "about 90%" based on the WHO's early investigation protocol.
And on Tuesday, researchers at the University of Bonn launched an antibody study of 1000 people in the western German region of Heinsberg, the site of one of Germany's largest outbreaks. (Many residents were apparently infected at a local carnival celebration in the village of Langbroich-Harzelt in late February.) Virologist Hendrik Streeck of Bonn's University Hospital says he and his colleagues used WHO's protocols to help shape their study. He says initial results could be announced as early as next week.
Such studies could resolve whether confirmed cases are scarce in children and teens because they typically have mild disease, and thus are less likely to get tested, or because they are less likely to get infected in the first place. That information is crucial for deciding how much the virus might spread at schools and daycare centers. The studies might also provide clues about what percentage of the population already has some immunity to the virus.
"The fact that we're talking about all these studies just 3 months [after the disease was first recognized] is incredible," Van Kerkhove says. However, she adds that any results will be preliminary. "We want to latch on to any information that comes out," she says. "But we do need to interpret these initial results with caution." Solidarity II could provide the solid answers everyone is waiting for.