The vaccine rollout crawls forward. Most of us will spend weeks, or months, waiting. Great Britain did better. As of today, one-third of the English are already vaccinated, twice as many as in America. Why? A big reason is that our government decided to rigidly follow its regimen for the Moderna and Pfizer vaccines: two doses, about a month apart. But why insist on two doses? The Moderna and Pfizer vaccines are about 90% effective after one dose, according to clinical trial data.