If we need a booster dose, does that mean that the vaccines aren’t working?

No. COVID-19 vaccines are working well to prevent severe illness, hospitalization, and death, even against the widely circulating delta variant. However, public health experts are starting to see reduced protection, especially among certain populations, against mild and moderate disease. With cases of COVID-19 still high across the United States and increasing in some parts of the country, the latest CDC recommendations on booster doses help to ensure more people across the U.S. are better protected against COVID-19. 

Added November 22, 2021