Use of mRNA COVID-19 vaccines should be considered as the preferable option in the United States rather than Johnson & Johnson’s (J&J) Janssen COVID-19 vaccine in women aged under 50 years, according to one group of experts.
The group made their recommendation in an editorial in JAMA published online April 30, 2021, accompanying a paper describing details of 12 case reports of cerebral venous sinus thrombosis (CVST) with thrombocytopenia following the J&J COVID-19 vaccine, also known as the Ad26.COV2.S vaccine.
The editorialists are Ruth A. Karron, MD, professor of international health at Johns Hopkins University, Baltimore; Nigel S. Key, MD, professor of hematology at the University of North Carolina at Chapel Hill; and Joshua M. Sharfstein, MD, associate dean for public health practice at Johns Hopkins
They noted that, after an initial pause following reports of thrombosis with thrombocytopenia syndrome (TTS) linked to the J&J vaccine, and on the recommendation of the Advisory Committee on Immunization Practices, the United States has permitted the use of the J&J vaccine in all adults with information on the risk of TTS added to educational materials.
The editorialists pointed out that no cases of TTS have been confirmed following administration of more than 180 million doses of the mRNA vaccines in the United States.
They said that, while the J&J vaccine will still be needed for individuals with allergies to components of the mRNA vaccines and for those who live in remote locations where the cold chain for transport and storage of mRNA vaccines cannot be maintained, “U.S. public health agencies and clinicians should consider recommending mRNA vaccines as safer options for those who may be at substantially higher risk for TTS after Ad26.COV2.S vaccination, currently women younger than 50 years.”
In the main JAMA paper, a group led by Isaac See, MD, Centers for Disease Control and Prevention COVID-19 Response Team, reported full details of 12 cases of CVST with thrombocytopenia following the J&J COVID-19 vaccine reported to the U.S. Vaccine Adverse Event Reporting System (VAERS).
The 12 U.S. case reports, 3 of which were fatal, show many similarities to cases described in Europe after the AstraZeneca vaccine.
The authors noted that, by April 12, approximately 7 million doses of the J&J vaccine had been given in the United States. The 12 cases of CVST and thrombocytopenia following receipt of the vaccine were reported to VAERS between March 2 and April 21. All 12 cases were in White women, 11 of whom were aged under 50 years.
As of April 25, a further two cases have been confirmed and reported to VAERS; one in a man younger than 40 years, the other in a woman aged between 40 and 59 years.
In the 12 cases reported in detail, symptoms started between 6 and 15 days post vaccination.
At least one risk factor for CVST was identified in seven patients (obesity in six, hypothyroidism in one, and use of combined oral contraceptives in one). None of the patients was pregnant or within 12 weeks post partum, had prior thrombosis, a personal or family history of thrombophilia, or documented prior exposure to heparin.
In addition to CVST, seven patients had intracerebral hemorrhage and eight had non-CVST thromboses.
One patient reported a history of SARS-CoV-2 infection approximately 4 months prior to vaccination. Of the other 11 patients, 4 had negative serologic tests and 7 were not tested.
All 12 patients were hospitalized and 10 were admitted to an ICU. At the time of the last follow-up, three patients had died (all of whom had intraparenchymal hemorrhage), three remained in the ICU, two were still hospitalized but not in an ICU, and four had been discharged home.
The authors pointed out that the U.S. cases of CVST with thrombocytopenia following the J&J vaccine have many similarities to those reported in Europe after the AstraZeneca vaccine, occurring primarily in women younger than 40 years and in patients without diagnosed thrombophilia. Both European and U.S. patients had a median platelet nadir count of 19 x 103/mcL and several also had non-CVST large-vessel thrombosis.
In the European cases of CVST with thrombocytopenia, 50% of patients died, compared with 25% of U.S. patients.
Like the European cases, the U.S. cases had positive heparin-PF4 HIT antibody enzyme-linked immunosorbent assay tests in the absence of prior exposure to heparin, as would be seen in autoimmune HIT.
However, in the initial European CVST reports, 88% of patients tested with functional platelet HIT antibody tests had positive results, compared with only 11% of the U.S. cases. But the authors noted that lack of standardization in functional platelet HIT antibody assays may lead to differences in results by different laboratories.
“It may be important to notify testing laboratories that postvaccination TTS is being evaluated, so that testing methods can be adjusted if needed,” they said.
They concluded that these case reports suggest that the pathogenesis of TTS may be similar to autoimmune HIT, triggered by the formation of antibodies directed against PF4, a constituent of platelet alpha granules released during platelet activation. In contrast to classic HIT in which exogenous heparin triggers antibody formation, in autoimmune HIT, an endogenous polyanion triggers PF4 antibody formation.
They noted that the precise mechanism of TTS in relation to COVID-19 vaccination has not yet been established. The Global Advisory Committee on Vaccine Safety has stated that a platform-specific mechanism related to adenovirus vector vaccines cannot be excluded. Both the J&J and AstraZeneca vaccines use an adenoviral vector, but they are different; J&J uses a human vector, while AstraZeneca uses a chimpanzee vector.
They also pointed out that CVST and thrombocytopenia following SARS-CoV-2 infection has been reported in at least two cases, but HIT testing was not done in these cases. There have not so far been any reports to VAERS of CVST with thrombocytopenia following mRNA COVID-19 vaccines.
The authors said these findings have important clinical and public health implications, noting that the CDC has updated its interim clinical considerations for use of authorized COVID-19 vaccines to indicate that women aged 18-49 years should be aware of the increased risk of TTS after receipt of the J&J vaccine, and to use a nonheparin anticoagulant in suspected cases.
They noted that a subacute presentation of headache is present in 90% of patients with typical CVST. While headache is a common symptom after the J&J vaccination, most headaches begin and resolve within 2 days. Whereas in the U.S. cases of CVST after vaccination, headache symptoms began at least 6 days after vaccination and persisted for at least a week for most.
“Urgent consultation with a neurologist is prudent when a patient is suspected or confirmed to have CVST. In addition, since the median time from symptom onset to hospitalization was 7 days in the U.S. CVST case series, patient and clinician education might shorten the time to clinical evaluation and therefore treatment,” they stated.
The authors also note that VAERS is a passive surveillance system, so cases of CVST with thrombocytopenia may be underreported.
In their accompanying editorial, Dr. Karron and colleagues pointed out that, in addition to the 12 patients with CVST with thrombocytopenia described in this case series, at least three patients without CVST but meeting diagnostic criteria for TTS have been reported to VAERS (as of April 21), all in women aged 18-59 years (median age, 37 years).
The editorialists reported that the rate of CVST with thrombocytopenia after the J&J vaccine is approximately 5 per million women aged 18-50 years. This is compared with a background rate of approximately 0.05-0.13 per million per month.
They said that the availability of an interim standardized case definition of this adverse effect will facilitate prospective case ascertainment through review of large linked databases and active case finding.
This will also permit greater understanding of whether individuals who are otherwise at increased risk for hypercoagulation in general and for CVST in particular (for example, women taking hormonal contraceptive medications or who are pregnant) are also at increased risk for TTS.
Obtaining this information will support dynamic country-specific assessments of the risks of each vaccine, compared with the risk of COVID-19 disease for their populations and subpopulations, they added.
A version of this article first appeared on Medscape.com.