The document discusses the effectiveness of the Johnson & Johnson COVID-19 vaccine. It states that while the vaccine only requires one dose and has logistical advantages over other vaccines, it has been shown to be only 72% effective compared to 95% for the Moderna and Pfizer vaccines. The Johnson & Johnson vaccine also poses serious health risks, with 15 cases of cerebral blood clots reported out of 8 million doses administered in the US. Due to these risks and lower effectiveness, experts have recommended against use of the Johnson & Johnson vaccine for all people over 18.