Do COVID-19 vaccines create new virus variants?

COVID-19 vaccines reduce the spread of the virus, reducing the likelihood that the virus will mutate to create new variants, according to Dr. Stuart Ray, a professor at Johns Hopkins University's medical school. Scientific evidence also shows many coronavirus variants emerged in the population before vaccines were available.

Experts say new variants likely evolved as a result of prolonged viral infections in the population, not vaccines, which are designed to prevent such infections.

With some viruses, such as dengue virus, scientists have observed a phenomenon called antibody-dependent enhancement, in which antibodies generated by a past infection or a vaccine will bind to a viral pathogen but not neutralize it. This can cause people who have antibodies to experience more severe symptoms if they are infected later. However, this has not occurred with the coronavirus or vaccines to prevent it.