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Citing the need for more information on risk factors, members of CDC's Advisory Committee on Immunization Practices (ACIP), during an , agreed that the pause on Johnson & Johnson's COVID-19 vaccine should be extended.

There was no official vote, but members recommended reconvening as soon as additional risk/benefit and risk refinement data become available on the cases of abnormal clotting seen with the vaccine. In particular, the committee wants to know what risk factors, such as age and gender, may be at play so as to inform definite recommendations. Most committee members did not wish to vote at all due to the lack of data.

The ACIP working group enumerated all the unknowns involving the vaccine, including true background incidence of cerebral venous sinus thrombosis (CVST) with thrombocytopenia, specific risk factors for thrombocytopenic thromboembolic events and true incidence of thrombocytopenic thrombotic events after the Johnson & Johnson COVID-19 vaccine, as more cases may be identified in the coming days.

Tom Shimabukuro, MD, of the CDC, reviewed details of the . He noted observed cases of CVST following the vaccine were 3-fold greater than background rates of CVST among women ages 20-50, but noted this did not apply to CVST with thrombocytopenia -- the condition triggering the uproar around both the Johnson & Johnson and AstraZeneca vaccines -- as this was too rare a complication.

The six cases were in white women ages 18-48 with few common risk factors. Their median age was 33, with a median time to symptom onset of 8 days after vaccination. No patients were pregnant or postpartum, and only one was on oral contraceptives. Comorbidities varied: three patients had obesity, one with hypothyroidism, one with hypertension, and one with asthma. None had known coagulation disorders.

Five of six cases had headache as an initial presenting feature. Late presentations included severe headache or abdominal pain. In four of the six, thrombocytopenia was severe.

Three of six cases involved thromboses not limited to the cerebral venous drainage system, including two occurring in the portal vein. Shimabukuro said in the future, they would "cast a little wider net" to include thromboses in the presence of thrombocytopenia, not necessarily limited to the central nervous system.

Five patients were treated with argatroban, four with heparin (which the FDA and CDC warned against) and three apiece with platelets or intravenous immunoglobulin. Three patients were hospitalized, two in the ICU. Two were discharged home.

Liaison member Doran Fink, MD, PhD, of the FDA, proposed a "risk management approach," where these risks could be addressed in the Johnson & Johnson vaccine emergency use authorization fact sheet "to inform healthcare professionals and vaccine recipients of potential risks."

However, there seemed to be little appetite among ACIP members for making any recommendation about the vaccine until more data are available. The committee also was not eager to extend the pause for some groups and not others, citing a lack of data in additional populations such as men and older adults.

They agreed to reconvene, potentially in a week to 10 days, by which time more may be known about the risk.

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