Millions of Americans have immune disorders or autoimmune diseases — such as lupus, rheumatoid arthritis or Crohn’s disease — that require them to take immune-suppressing treatments for life. Because people with compromised immune systems were largely excluded from the Covid-19 vaccine trials in the U.S. and globally, it’s unknown how much protection they get from vaccination. … Researchers at the NIH are currently recruiting participants across the country to be tested before and after they receive their Covid-19 vaccinations.