Findings from a study published in NPJ Vaccines assessed the risk of retinal vascular occlusion (RVO) after COVID-19 vaccination and the probability of retinal vascular events.
Give me some background first.
RVO following COVID-19 vaccination is an uncommon adverse event caused by thromboembolism due to vessel compression, vasospasm, or degeneration of vascular walls.
However, recent studies have linked retinal vascular events with four COVID-19 vaccines, including:
- BNT162b2 (Pfizer-BioNTech)
- mRNA-1273 (Moderna)
- CHAdOx1 (Oxford/AstraZeneca)
- Ad26.COV2.S (Janssen-Johnson&Johnson)
Of note, the quality of the data from previous studies was insufficient to demonstrate a causal relationship between RVO and COVID-19 vaccines.
Now, talk about the study.
In this multicenter retrospective cohort study, researchers used the TriNetX global network and included over 745,041 individuals frowho received COVID-19 vaccines between January 2020 and December 2022.
Per the Johns Hopkins Institute for Clinical and Translational Research, TriNetX is a self-service, web-based data exploration tool which helps clinical researchers to define a patient cohort using curated data and inclusion and exclusion criteria to explore cohort attributes.
Tell me more.
These results were compared with a 1:1 propensity score match of a control unvaccinated cohort.
Individuals with a history of RVO or those who took any systemic medications that could potentially impact blood coagulation 4 months prior to vaccination were excluded from the study.
Findings?
Participants who received a COVID-19 vaccination had a higher risk of all forms of RVO 2 years after vaccination (hazard ratio [HR] 2.19, 95% confidence interval [CI] 2.00-2.39).
The cumulative incidence of RVO was notably higher in the vaccinated cohort in comparison to the unvaccinated cohort at both 12 weeks and 2 years after vaccination.
Go on…
The risk of RVO significantly increased during the 2 weeks after vaccination and continued through 12 weeks.
Further, participants with the first and second doses of Pfizer-BioNTech and Moderna had a significantly increased risk of RVO 2 years following vaccination.
However, no disparity was observed between the brand and dose of COVID-19 vaccines.
Any limitations?
The key limitations of this study include the following:
- RVO being defined by diagnostic codes (so diagnostic accuracy could not be confirmed)
- The TriNetX database provided no p-values for analysis
- The potential presence of residual confounding variables
- Underreporting of RVO may have occurred due to RVO patients with mild or no symptoms
- Losing patients who followed up at institutions not included in the TriNetX database
Expert opinion?
Thrombocytopenia is a condition in which individuals have a low platelet count in their blood, and thrombosis that manifests prior to thrombocytopenia is referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT).
The study authors noted, “Two adenoviral vector-based immunizations, CHAdOx1 and Ad26.COV2.S, have been associated with the development of VITT.”
Of note, reports of this adverse event are very rare.
Take home.
The size of this study strengthens the findings of previous investigations, suggesting a strong correlation between COVID-19 mRNA vaccines (i.e., Pfizer-BioNTech and (Moderna) and RVO.
However, establishing a definitive association between the two is complicated by the fact that there is limited evidence and low frequency of RVO.
As such, the study authors recommended that “individuals without a history of severe allergic reaction to any component of the vaccine be vaccinated to protect against COVID-19” because the incidence of RVO remains extremely low.