• Samantha Albert, Moretti Collins, Tiara Cummings, Mary Ann Comunale

COVID-19 and Blood Clots: Why it is Safe to be Vaccinated

Updated: Jul 2, 2021

The Pause: Just when the vaccine rollout was picking up speed, the emergency brake was pulled on two vaccines. COVID-19 vaccinations with the Johnson and Johnson Inc. (J&J) and AstraZeneca (AZ) vaccines have recently been paused out of an abundance of caution while scientists investigated an extremely rare issue with blood-clotting events occurring in some people who received these vaccines. The vaccines are similar in that they both use a viral vector platform (EEE). The J&J vaccine is available in the US and the UK, but the US Food and Drug Administration (FDA) has not yet authorized the use of the AZ vaccine in the US. To date, there have been no reported cases of blood clotting reported in people who have received COVID-19 vaccines by Pfizer Inc./BioNTech SE or Moderna Inc, both of which use an mRNA platform.

The Investigation: As of the 21st of April, approximately 8 million doses of the J&J vaccine were administered in the US, and 15 cases have been reported (all in women) of a rare blood-clotting event, resulting in 3 deaths. In a joint effort, the FDA and the CDC examined the cases of cerebral (brain) venous sinus thrombosis (blood clotting)—a type of stroke that occurs in about 2-14 in a million people each year and is usually linked to an infection that stimulates an autoimmune event. What is different in the J&J vaccine cases is that it occurs together with thrombocytopenia (a condition that in which a person has a low platelet count). These two factors together have been identified as the “pattern” seen in these vaccine-related cases. This phenomenon can occur without vaccination but is so rare that there is no available data to establish a background level of cases. The vaccine-related cases have occurred at a rate of less than 2 in a million people vaccinated with the J&J vaccine. The European Medicines Association (EMA) has reported similar findings with the use of the AZ vaccine, with 10 cases reported in a million doses administered.

Patient Awareness: What should patients know? Anyone experiencing any of these symptoms within 3 weeks of being vaccinated with the J&J or AZ vaccines should see their physician immediately:

  • Shortness of breath

  • Chest pain

  • Leg swelling

  • Stomach pain that persists

  • Severe headaches or blurred vision

  • Small blood spots at the vaccine injection site

Resolution: After a brief pause that allowed scientists and clinicians to examine the blood-clotting phenomena, both vaccines are currently deemed safe in their respective regions and available again for use. Regulators are citing that the benefits of vaccination far outweigh the potential risks. In the US, the CDC and FDA have thoroughly reviewed all cases and updated their recommendations, case reporting, and specific treatment guidelines. In Europe, the EMA reported on the 20th of April that the vaccines will come with a blood clot warning and has advised those under 30 years of age to receive an alternative vaccine. In addition, physicians now have a heightened awareness to look for symptoms in vaccinated patients.


Speaking Plainly:

  • The J&J and AZ vaccines are highly effective, extremely low risk, and safe to receive.

  • Anyone that experiences symptoms of blood clots after receiving any vaccine should call their doctor.

  • Physicians are aware of these rare occurrences and have been updated on treatment guidelines.

  • Those who are eligible should be vaccinated as soon as possible with the available vaccine.