Daily Dose: How COVID-19 Vaccination Can Reduce Severity, Mortality after SARS-CoV-2 Infection

Patient Care brings primary care clinicians a lot of medical news every day—it’s easy to miss an important study. The Daily Dose provides a concise summary of one of the website's leading stories you may not have seen.

Last week, we reported on a study published in The Lancet Microbe that examined the longitudinal association of COVID-19 vaccination with cytokine and chemokine concentrations and trajectories among persons with SARS-CoV-2 infection.

The study

In the longitudinal, prospective cohort study, researchers collected blood samples from participants aged ≥18 years enrolled in a clinical trial that examined the efficacy of convalescent plasma therapy for ambulatory COVID-19 in 23 outpatient sites across the US.

In the current study, participants were limited to those with COVID-19 before vaccination or with breakthrough infections who had blood samples and symptom data collected at screening, day 14, and day 90 visits. Investigators analyzed the associations between COVID-19 vaccination status and concentrations of 21 cytokines and chemokines (measured using multiplexed sandwich immunoassays) using multivariate linear mixed-effects regression models that were adjusted for age, sex, body mass index, hypertension, diabetes, convalescent or control plasma, and COVID-19 waves (prealpha or alpha and delta).

Overall, 882 participants were enrolled in the study between June 29, 2020, and September 30, 2021, of whom 57% were women, 78% were unvaccinated, 6% were partly vaccinated, and 16% were fully vaccinated at baseline. Among the unvaccinated group, 37% were aged ≥50 years and 21% of the fully vaccinated group were aged ≥50 years.

The findings

After adjusting for confounders, researchers observed that geometric mean concentrations of interleukin (IL)-2RA, IL-7, IL-8, IL-15, IL-29 (interferon-λ), inducible protein-10, monocyte chemoattractant protein-1, and tumor necrosis factor-α were significantly lower among the fully vaccinated group than in the unvaccinated group at screening.

At day 90, fully vaccinated persons had approximately 20% lower geometric mean concentrations of IL-7, IL-8, and vascular endothelial growth factor-A than unvaccinated participants. Also, results showed that cytokine and chemokine concentrations decreased over time in the fully and partly vaccinated groups as well as in the unvaccinated group.

Authors' commentary

"These findings suggest that vaccination might have short-term and long-term benefits after symptomatic infection and indicates a mechanistic explanation for the significantly reduced disease severity and mortality among vaccinated cohorts. Thus, it is essential to raise public awareness of the benefits of vaccination and guarantee equitable distribution of vaccines globally."

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