The Medical Letter on Drugs and Therapeutics
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1623
In Brief: Johnson & Johnson COVID-19 Vaccine Suspended (online only)
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On April 13, 2021, the FDA and CDC advised suspending use of the Johnson & Johnson adenovirus-based COVID-19 vaccine while the agencies investigate 6 cases of cerebral venous sinus thrombosis (CVST) and thrombocytopenia that occurred following administration of the vaccine.1,2 In an April 14 emergency meeting, the Advisory Committee on Immunization Practices (ACIP) recommended continuing the suspension until more data become available. About 7 million people in the US have received the Johnson & Johnson vaccine.1-3

All 6 cases occurred in women 18-48 years old. Symptom onset occurred 6-13 days after administration of the single-dose vaccine. In addition to CVST, three of the women had extracranial thromboses. Four women developed intraparenchymal brain hemorrhage, and one died. Comorbid conditions included obesity (n=3), hypertension (n=1), hypothyroidism (n=1), and asthma (n=1); one woman was taking estrogen/progesterone.1-3

CVST with thrombocytopenia has also been reported with the Oxford/AstraZeneca adenovirus-based COVID-19 vaccine (not authorized for use in the US). With both adenovirus-based vaccines, incidence of CVST with thrombocytopenia has been associated with high serum levels of antibodies against platelet factor 4 (PF4)-polyanion complexes similar to those that occur in heparin-induced thrombocytopenia (HIT). No cases of CVST with thrombocytopenia have been associated with the ~180 million Pfizer and Moderna mRNA-based COVID-19 vaccine doses administered in the US.3-5

The CDC recommends that persons who experience a thrombotic event and thrombocytopenia after administration of the Johnson & Johnson vaccine be screened with a PF4 HIT enzyme-linked immunosorbent assay (ELISA) and referred to a hematologist. If the assay is positive or cannot be completed, heparin should not be used for thrombosis management; other anticoagulants and intravenous immune globulin should be considered instead.2

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