The Centers for Disease Control and Prevention published three studies on Wednesday, highlighting the protection against COVID-19 given by vaccines declined in the midsummer months when the more contagious delta variant rose to dominance in the United States.
However, protection against hospitalisation was strong for weeks after vaccination, indicating the shots will generate immune fighters that stave off the worst effects of the virus and its current variations.
Data from these studies also reinforced the idea that vaccines alone are unlikely to lift the United States out of the pandemic. Masks and other precautions need to be part of the approach.
“Masks and other precautions should be part of a layered approach centered on vaccination,” wrote researchers from the New York State Department of Health and the University at Albany School of Public Health in their study of vaccine effectiveness across New York state.
Many factors influence vaccine effectiveness and the changes the scientists observed in New York cannot be attributed to delta with certitude, they noted.
“But if vaccinated people behave in riskier ways, such as not wearing masks in crowded areas, that may influence vaccine effectiveness”.