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Review of "Hematologic Abnormalities after COVID-19 Vaccination: A Large Korean Population-based Cohort Study"

Reviewers: S I V Ferrer (Instituto Nacional de Ciencias Médicas y Nutrición) | 📒📒📒 ◻️◻️

Published onJun 28, 2024
Review of "Hematologic Abnormalities after COVID-19 Vaccination: A Large Korean Population-based Cohort Study"
key-enterThis Pub is a Review of
Hematologic abnormalities after COVID-19 vaccination: A large Korean population-based cohort study
Hematologic abnormalities after COVID-19 vaccination: A large Korean population-based cohort study
Description

Abstract Adverse hematologic events have been reported after COVID-19 vaccination. The objective of this study was to investigate whether hematologic abnormalities develop after COVID-19 vaccination. Retrospective cohort analyses of data from the Korean National Health Insurance Service (KNHIS) database were conducted from July 2022 to August 2023. We randomly selected data of half of those living in Seoul City as of January 1, 2021 with their diagnostic records up to December 31, 2021. The included participants were vaccinated and nonvaccinated persons aged 20 years or older (n= 4,203,887). Hematologic abnormalities after COVID-19 vaccination were identified as nutritional anemia, hemolytic anemia, aplastic anemia, coagulation defects, and neutropenia using International Classification of Diseases, Tenth Revision codes after index date. Incidence rates of hematologic abnormalities in the vaccination group 3 months after vaccination were significantly higher than those in the nonvaccinated group: 14.79 vs. 9.59 (P<.001) for nutritional anemia, 7.83 vs. 5.00 (P<.001) for aplastic anemia, and 4.85 vs. 1.85 (P<.001) for coagulation defects. COVID-19 mRNA vaccine was associated with higher development of nutritional anemia (odds ratio [OR], 1.230 [95% CI, 1.129-1.339], P<.001) and aplastic anemia (OR, 1.242 [95% CI, 1.110-1.390], P<.001) than the viral vector vaccine. The risk of coagulation defects was increased (OR, 1.986 [95% CI, 1.523-2.589], P<.001) after vaccination, and there was no risk difference between mRNA vaccine and viral vector vaccine (OR, 1.075 [95% CI, 0.936-1.233], P=.306). In conclusions, COVID-19 vaccination increased the risk of hematologic abnormalities. When administering the COVID-19 vaccine, careful observation will be necessary after vaccination.

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Summary of Reviews: This retrospective cohort analysis claims that COVID-19 vaccination is associated with an increased risk of hematologic abnormalities, such as nutritional anemia, aplastic anemia, and coagulation defects compared to nonvaccinated individuals. The reviewer points out several limitations including population characteristics and bias and confounders such as sex, age, and pre-existing conditions. Overall, they find the study potentially informative as previous studies have claimed COVID-19 vaccines to have very few hematologic adverse effects. 

Reviewer 1 (Sergio Iván Valdés F…) | 📒📒📒 ◻️◻️

RR:C19 Strength of Evidence Scale Key

📕 ◻️◻️◻️◻️ = Misleading

📙📙 ◻️◻️◻️ = Not Informative

📒📒📒 ◻️◻️ = Potentially Informative

📗📗📗📗◻️ = Reliable

📘📘📘📘📘 = Strong

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