Impact of vaccination on keratoplasty

COVID-19 vaccination and corneal allograft rejection- a review

Aim

To provide a comprehensive literature review on the perceived correlation between COVID-19 vaccination and corneal allograft rejection, and to characterize risk factors, time course, graft outcomes and proposed immunological basis.

Methods

A literature review was conducted in August 2023 using 4 electronic databases: PubMed, EMBASE, MEDLINE and Scopus. Articles were sourced using key words associated with COVID-19 vaccination and corneal graft. All articles were screened for relevance by abstract review. Duplicates and articles related to COVID-19 infection were excluded. No time limits were set. Additional literature searches regarding cause of corneal graft rejection, rates of graft rejection associated with other vaccines and the cellular mechanism of rejection were also performed.

Results

262 articles were identified from the literature search. 37 papers were included in the analysis based on defined inclusion criteria. This consisted of systematic reviews (n=6), review articles (n=5), retrospective studies (n=3), case series (n=8), letter to the editor (n=1) and case reports (n= 14). The majority of reported allograft rejections were in penetrating keratoplasties. Risk factors for COVID-19 vaccination associated rejection were previous allograft rejection episodes, repeat grafts and penetrating keratoplasty. Most reported rejection episodes were mild and resolved with treatment. Notably, several studies reported nil increase in corneal allograft rejection episodes over the COVID-19 vaccination period. Rejection episodes are associated with a broad spectrum of other vaccines and the complete pathophysiology is undetermined.

Conclusion

Corneal allograft rejection appears to be a rare complication of COVID-19 vaccination most frequently observed in high-risk corneal transplants. The true extent of this correlation remains controversial; however, clinician awareness of this risk is essential to its mitigation. Patient counselling around symptom monitoring following vaccination and discussion around topical steroid prophylaxis may be prudent.

Examining the Influence of COVID-19 Infection and Pandemic Restrictions on the Risk of Corneal Transplant Rejection or Failure: A Multicenter Study

PURPOSE

The purpose of this study was to evaluate two aims. The first was whether patients with a history of keratoplasty who developed COVID-19 were at a higher risk of corneal graft rejection or failure. The second was examining whether patients who underwent a new keratoplasty during the first 2 years of the pandemic from 2020-2022 were at a higher risk of the same outcomes compared to those undergoing keratoplasty from 2017-2019 before the pandemic.

METHODS

A multicenter research network, TriNetX, was used to query for keratoplasty patients with or without a COVID-19 between January 2020 and July 2022. Additionally, the database was also queried to identify new keratoplasties performed from January 2020-July 2022 and compare it to keratoplasties performed during a similar pre-pandemic interval between 2017-2019. 1:1 Propensity Score Matching was utilized to adjust for confounders. Graft complication of either a rejection or failure was assessed within 120 day follow-up using the Cox proportional hazard model and survival analysis.

RESULTS

A total of 21,991 patients with any keratoplasty history were identified from January 2020-July 2022, of which 8.8% were diagnosed with COVID-19. Matching revealed two balanced cohorts of 1,927 patients where no significant difference in risk of corneal graft rejection or failure among groups ((aHR [95% CI] = 0.76 [0.43,1.34]; p = .244)). Comparing first-time keratoplasties performed in a pandemic period of January 2020-July 2022 to a corresponding pre-pandemic interval from 2017-2019 also similarly revealed no differences in graft rejection or failure in matched analysis (aHR = 0.937[0.75, 1.17], p = .339).

CONCLUSIONS

This study found no significant increase in the risk of graft rejection or failure in patients with a prior keratoplasty history following COVID-19 diagnosis nor in any patients who had a new keratoplasty done during 2020-2022 when compared to a similar pre-pandemic interval.