Six months of coronavirus: the mysteries scientists are still struggling to solve.

With governments and industry injecting billions into the development, testing, and manufacturing of vaccines, scientists say, a vaccine may be available in record time, but it simply may not be fully effective. “We could have vaccines in the clinic that are useful in people within 12 or 18 months,” Dave O’Connor, a virologist at the University of Wisconsin-Madison, told Nature in May. “But we’re going to need to improve them.