Covid-19 vaccines from Moderna Inc. and from Pfizer Inc. and partner BioNTech SE are highly effective in preventing infections in real-world conditions, further evidence that vaccinations can slow the spread of the virus.

The vaccines were 90% effective at minimizing the risk of infection two weeks after the second dose, according to a study of almost 4,000 healthcare workers, first responders and other essential workers published by the US Centers for Disease Control and Prevention on Monday.

In addition, the data showed that the vaccines can reduce the risk of coronavirus infections whether or not they cause symptoms.

“This study shows that our national vaccination efforts are working, “ CDC Director Dr. Rochelle Walensky stated. “The authorized vaccines are the key tool that will help bring an end to this devastating pandemic.”