Johnson & Johnson’s Janssen COVID-19 Vaccine: CDC and FDA have recommended that use of Johnson & Johnson’s Janssen (J&J/Janssen) COVID-19 Vaccine resume in the United States, effective April 23, 2021. However, women younger than 50 years old especially should be aware of the rare risk of blood clots with low platelets after vaccination, and that other COVID-19 vaccines are available where this risk has not been seen. If you received a J&J/Janssen vaccine, here is what you need to know. Read the CDC/FDA statement.