Amid reports of vaccine shortages occurring around the world, a new study [pdf] suggests that people who have already had COVID-19 should get only one shot of the mRNA vaccine to avoid possible unnecessary adverse reactions and free up supplies for those who need it more. The study, which hasn’t been peer-reviewed, evaluated vaccine reactions after receiving the first dose in 231 individuals—83 with a past infection of the CCP (Chinese Communist Party) virus and 148 who had never had an infection. Researchers found that both groups equally reported experiencing pain, swelling, and redness at the injection site at the time of vaccination, which improved in a couple of days. However, people with a prior infection experienced more severe systemic reactions—fever, headache, chills, muscle or joint pain, and fatigue—than those who had never been infected. “We also noted that vaccine reactogenicity [expected reactions] after the first dose is substantially more …