CNN — Covid-19 vaccines are known to be safe and effective, and they’re available for free, but many Americans in the US refuse to get them – and a recent study suggests that celebrities may share some of the blame for people’s mistrust. Celebrities have long tried to positively influence public health, studies show, but during the Covid-19 pandemic, they also seemed to have a large influence on spreading misinformation. Decades ago, in the 1950s, people could see stars like Elvis Presley, Dick Van Dyke and Ella Fitzgerald in TV ads that encouraged polio vaccination. This celebrity influence boosted the...