A study published Monday said that those who received the Johnson & Johnson single-shot COVID-19 vaccine were more likely to experience a certain type of blood clotting issue than among individuals in the general population before the start of the pandemic, although researchers said that the blood clots are rare. Researchers with the Mayo Clinic, who published their findings in the JAMA Internal Medicine journal, obtained data on blood clotting from Olmsted County, Minnesota, between 2001 and 2015. They then compared rates of blood clotting with those who received the Johnson & Johnson shot. Individuals who got the vaccine were 3.5 times more likely to develop cerebral venous sinus thrombosis (CVST) than among the general population between 2001 and 2015, they found. The researchers said that the study adjusted for sex and age to make a comparison. CVST occurs when a blood clot occurs in the brain’s venous sinuses, which prevents blood from exiting …