In the debate over how long the protection from COVID-19 vaccines last, radiology has now entered the chat. A new study in Radiology shows that people with COVID who got vaccinated more than eight months before COVID diagnosis had more severe clinical findings on imaging exams.
The rapid development of COVID vaccines and their rollout worldwide has been one of the biggest public health success stories of the last 100 years.
- Still, even the most effective vaccines lose their potency over time, and COVID vaccines are no different.
The question is, how long does the COVID vaccine’s protection last?
- Previous research documented a decline during the Delta and Omicron waves in vaccine effectiveness against hospitalization, from 92% to 79% after 224-251 days, and a drop in efficacy against death from 91% to 86% after 168-195 days in those with severe COVID.
To shed more light on the issue, researchers in South Korea performed imaging exams on 4.2k patients with COVID from June 2021 to December 2022.
- They correlated the severity of clinical outcomes like pneumonia visible on imaging exams to the length of time between patient diagnosis and when they had been vaccinated.
Compared to those vaccinated in the last 90 days before COVID diagnosis, people vaccinated more than 240 days …
- Had almost twice odds of severe outcomes (OR = 1.94)
- Had higher odds of severe pneumonia on chest radiographs (OR = 1.65)
- But there was no difference in the odds of severe outcome between those vaccinated in the last 90 days and those vaccinated 91-240 days before diagnosis
In an interesting wrinkle to the study, the researchers found no statistically significant difference in odds of severe pneumonia visible on chest CT scans between those vaccinated more than 90 days before diagnosis and those vaccinated within 90 days.
- The authors proposed that the low use of CT for pneumonia assessment in their study population (20%) and its use primarily for critically ill patients could have introduced bias into the results.
The Takeaway
The new findings shed light on the declining potency of COVID vaccines over time and could inform public debate over the length of time between boosters. The research also dovetails with other studies showing that the vaccine’s effectiveness does indeed begin to wane at six months.
