Under Trump, Republicans touted the coronavirus vaccines. Now, under Biden, they’re questioning them. - The Washington Post

… The false and misleading claims about the vaccines from these Republicans are directly refuted by data showing the vaccines approved for use in the United States are overwhelmingly safe and effective. But those false and misleading claims track with a Republican voter base that is skeptical of getting vaccinated, in part because of said false and misleading claims...
https://www.washingtonpost.com/politics/2021/07/14/under-trump-republicans-touted-coronavirus-vaccines-now-under-biden-theyre-questioning-them/