SARS-CoV-2 Vaccination — An Ounce (Actually, Much Less) of Prevention

The Covid-19 epidemic continues to rage, especially in countries that have been unable or unwilling to institute strong public health measures. A return to normality has increasingly come to rely on the success of vaccines to prevent disease and, we hope, limit further spread of infection. However, this hope has been tempered by several unknowns. No existing vaccines have been shown to be effective against infection with any betacoronavirus, the family that includes SARS-CoV-2, which causes Covid-19. SARS, caused by another betacoronavirus, ended on its own before serious efforts at vaccine development were undertaken, and the rather small number of . . .