Researchers urgently want to know how long the current crop of effective COVID-19 vaccines protect against infection and also would like a quicker and more efficient way to test the efficacy of new vaccines. They are trying to check both of those boxes by studying antibody levels in people already exposed to the new coronavirus.
A study at Oxford University is deliberately exposing previously infected healthy young volunteers to the coronavirus again, using blood tests to learn what level of antibodies will protect people against getting sick again. "It may be not possible to reinfect with an antibody level above a certain amount," lead investigator Helen McShane told NPR News. When researchers find that level of antibodies — or antibody cutoff titer — they can develop blood tests to determine how long vaccines are effective.
A separate study involving the U.S. government's Biomedical Advanced Research and Development Authority (BARDA), the Fred Hutchinson Cancer Research Center, and Moderna is also trying to find the cutoff titer by examining antibodies in people who got COVID-19 symptoms after getting inoculated with Moderna's vaccine. "Because the Moderna vaccine is so very effective, it's taken a very long time to collect enough from the vaccinated individuals who became infected," BARDA's Chris Houchens tells NPR. Now that they have data from enough people, they should soon be able to calculate whether a certain level of antibodies can show that new vaccines are effective without having to test the vaccines on tens of thousands of people. You can listen to NPR's report below. Peter Weber