Until now, research about the vaccine’s effect on older people has been minimal and short term. Of the 21,720 people who received the Pfizer-BioNTech vaccine rather than the placebo in its phase 3 trial, 7,971 or 37% were over age 55. Pfizer’s study did not include a breakout for those 65 and older. In the Moderna phase 3 trial, of the 15,181 volunteers given the vaccine rather than the placebo, 3,763 or 25 percent were older than 65.