Post-SARS-CoV-2 vaccination thrombosis is frequent and ubiquitous.

Dear Editor,

We eagerly read the article by Sonawane et al.[1] about central retinal vein occlusion in a 50-year-old male (case 1) and a 43-year-old female (case 2) 4 days and 3 days following the second dose of the AstraZeneca SARS-CoV-2 vaccine, respectively. The study is appealing but raises concerns.

We do not agree that the index cases are the first reported cases of SARS-CoV-2 vaccination-associated retinal vein thrombosis.[1] Retinal vein thrombosis following SARS-CoV-2 vaccinations has been reported in at least 27 other patients before [Table 1].

Table 1

Patients reported with SARS-CoV-2 vaccination associated retinal vein thrombosis till the end of December 2021

Age	Sex	Vaccine	Reference
50	m	AZV	[1]
47	f	AZV	[1]
71	f	BPV	[Tanaka 2021]
74	m	BPV	[Tanaka 2021]
51-85	m (n=11), f (n=10)	AZV (n=8), BPV (n=12)	[Park 2021]
74	f	Moderna	[Sacconi 2021]
54	f	Moderna	[Ikegami 2021]
52	m	BPV	[Endo 2021]
50	m	BOV	[Bialasiewicz 2021]

AZV: AstraZeneca vaccine, BPV: Biontech Pfizer vaccine, F: Female, M: Male

Thrombo-embolic events are a well-established complication of SARS-CoV-2 vaccines.[2] They may not only occur in the ocular veins but also in almost all other venous beds, including cerebral veins, deep leg veins, pulmonary veins, renal veins, portal veins, and others.

The increased thrombo-embolic risk following SARS-CoV-2 vaccinations may not only be due to immune thrombocytopenia or antibodies against PF4[1] but also due to impaired binding of coagulation factor-X to the virus capsid[3] or due to endothelial dysfunction.[4]

We do not agree with the statement that “a few cases of neurological adverse effects have been reported post-vaccination.”[1] Neurological side effects are the most frequent complications not only of SARS-CoV-2 infections but also of SARS-CoV-2 vaccinations. According to a recent review about the neurological side effects of SARS-CoV-2 vaccinations, 3051 patients with headache, 389 patients with Guillain–Barre syndrome, 312 with venous sinus thrombosis, 11 with transverse myelitis, and <5 with facial palsy, small fiber neuropathy, immune encephalitis, reversible cerebral vasoconstriction syndrome, multiple sclerosis, neuromyelitis optica, ischemic stroke, intracerebral bleeding, Tolosa–Hunt syndrome, hypophysitis, epilepsy, hyperactive encephalopathy, and acute, disseminated encephalomyelitis have been reported till the end of September 2021.[5] If hyposmia/anosmia and ageusia/dysgeusia are regarded as neurological abnormalities, the number of neurological complications is even higher.

Overall, the study has several limitations which challenge the results and their interpretation.

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Ethics statement

The study was approved by the institutional review board.

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The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.