Which vaccine is the best?

Many people wonder if they should get the single dose Johnson & Johnson vaccine or one of the two shot mRNA vaccines (Pfizer and Moderna). The answer for most people is that the best vaccine is one that is available to get.  However, there are some important differences to think about.

The similarities? All three vaccines are safe and effective at preventing COVID, and protection lasts for at least 6 to 8 months (and probably even longer). However, the mRNA vaccines are holding up even better against the delta variant.

The major differences between the two-shot mRNA vaccines and the one-shot J&J vaccine  are the vaccine technology, the dosing schedule, and side effects.  

  1. The two-shot vaccines use mRNA technology and the one-shot vaccine is a viral vector. Read about the vaccine types in another COVID-101 post here
  2. mRNA vaccines require two doses spaced 3 weeks apart for Pfizer and 4 weeks for Moderna. The Johnson & Johnson vaccine requires only one dose.  
  3. The Johnson & Johnson vaccine has been linked with the rare but serious side-effect of blood clots with low platelets. This occurs in about 7 women per one million women aged 18-49 years and is even more rare for older women and men.

Last update: Sept 23, 2021, 14:30 ET

Science review: SGB, ERS