4. There’s a lot we don’t know — about transmission, for example. Hewlett said we don’t have the data yet to understand whether, for example, J&J recipients contract or spread the virus more easily than those who got the Moderna or Pfizer vaccines. We also don’t know how long protection lasts, exactly, although the vaccines that were initially given out early in the year still seem to be effective. Still, these questions and more are why Prickett advises maintaining cautions in your life such as masking and social distancing.