In the past few weeks more than 7 million doses of Johnson & Johnson’s Janssen COVID-19 vaccine have been administered to people in the United States. In clinical trials of approximately 40,000 people, the J&J vaccine given as a single shot was 66% effective at preventing the illness due to the SARS-CoV-2 virus known as COVID-19. Because the J&J vaccine is a single shot, it has been preferred in some circumstances.
How is the J&J vaccine different from others?
The first available vaccines in the United States, produced by Pfizer and Moderna, use messenger RNA (mRNA) in their formulation to lead the body to develop a protective immune response against SARS-CoV-2 that effectively prevents COVID-19. The J&J vaccine, like the COVID-19 vaccine from AstraZeneca, is a viral vector vaccine, meaning it uses a different harmless virus (an adenovirus) that has been engineered to encode the spike protein of SARS-CoV-2 to trigger a protective immune response. Viral vector vaccines have been developed and tested in response to several other viruses.
What problems are being reported with the J&J vaccine?
Six cases of cerebral venous sinus thrombosis (CVST) have been reported in people who recently received the J&J vaccine in the United States. All cases occurred in women between 18 and 48 years of age, with symptoms occurring 6-13 days after vaccination. (Notably, during the clinical trial testing of the J&J vaccine, CVST occurred in one 25-year-old male subject 21 days after vaccination.) Of the six patients hospitalized with CVST, two were also diagnosed with splanchnic and portal vein thrombosis during hospitalization. Four patients developed intraparenchymal brain hemorrhage and one subsequently died.
Also reported with the J&J vaccine, CVST has been accompanied by thrombocytopenia. This may represent thrombotic thrombocytopenia, with the six CVST patients having platelet counts declining to between 10,000 and 127,000 per microliter during their hospitalization.
What causes the CVST and thrombocytopenia with the J&J vaccine?
It’s not yet clear if the J&J vaccine is causing these adverse events, and if so, what the mechanisms are. It is notable that these events are similar to other recent reports of thrombotic events with thrombocytopenia after receipt of the AstraZeneca COVID-19 vaccine in Europe, as both are viral vector vaccines. In Europe, after use of the AstraZeneca vaccine, some patients were diagnosed with immune thrombotic thrombocytopenia (ITP), where the pathogenesis may be associated with platelet-activating antibodies against platelet factor 4 (PF4), referred to as anti-PF4 antibodies.
What signs and symptoms may indicate CVST?
The most common symptoms with CVST are headache, blurred vision or altered sensation, fainting or loss of consciousness, confusion or difficulty speaking, seizures and coma. The initial presenting symptoms for the J&J vaccine patients included headache and back pain.
What is the treatment for CVST and thrombocytopenia associated with vaccine administration?
The general management of both CVST and immune or thrombotic thrombocytopenia should include standard therapy for these conditions irrespective of vaccine exposure. Anti-PF4, the heparin-PF4 antibody, can induce thrombotic thrombocytopenia in persons exposed to heparin; therefore, heparin should be avoided in patients with potential vaccine-associated thrombocytopenia unless heparin-induced thrombocytopenia (HIT) testing is negative, as it should be in patients with HIT. Per guidance from the Centers for Disease Control and Prevention, non-heparin anticoagulants and high-dose intravenous immune globulin should be considered in the treatment of patients who present with immune-mediated thrombotic events with thrombocytopenia after J&J COVID-19 vaccination. Consultation with a hematology specialist is recommended.
Recommendations for Critical Care Professionals From the CDC
- Maintain a high index of suspicion for symptoms that might represent serious thrombotic events or thrombocytopenia in patients who have recently received the J&J COVID-19 vaccine, including severe headache, backache, new neurologic symptoms, severe abdominal pain, shortness of breath, leg swelling, petechiae (tiny red spots on the skin), or new or easy bruising. Obtain platelet counts and screen for evidence of immune thrombotic thrombocytopenia.
- In patients with a thrombotic event and thrombocytopenia after receiving the J&J COVID-19 vaccine, evaluate initially with a screening PF4 enzyme-linked immunosorbent (ELISA) assay as would be performed for autoimmune HIT. Consultation with a hematologist is strongly recommended.
- Do not treat patients with thrombotic events and thrombocytopenia following receipt of J&J COVID-19 vaccine with heparin, unless HIT testing is negative.
- If HIT testing is positive or unable to be performed in a patient with thrombotic events and thrombocytopenia following receipt of J&J COVID-19 vaccine, non-heparin anticoagulants and high-dose intravenous immune globulin should be strongly considered.
- In the United States, report adverse events to the Vaccine Adverse Events Reporting System (VAERS), including serious and life-threatening adverse events and deaths in patients following receipt of COVID-19 vaccines.
References and additional material:
- Advisory Committee on Immunization Practices (ACIP). ACIP presentation slides: April 14, 2021 meeting. Accessed April 15, 2021. https://archive.cdc.gov/#/details?url=https://www.cdc.gov/vaccines/acip/meetings/slides-2021-04.html
- Abbott B. Do J&J and AstraZeneca vaccines cause blood clots, and what are the symptoms? Wall Street Journal. April 13, 2021. Accessed April 15, 2021. https://www.wsj.com/articles/j-j-astrazeneca-vaccines-blood-clots-11618329160?mod=djem10point
- Grady D, Zimmer C. J&J vaccine and blood clots: the risks, if any, are very low. New York Times. April 15, 2021. Accessed April 15, 2021. https://www.nytimes.com/2021/04/13/health/blood-clots-johnson-vaccine.html
