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Course: Association of mRNA Vaccination With Clinical and Virologic Features of COVID-19 Among US Essential and Frontline Workers

CME Credits: 1.00

Released: 2022-10-18

Key Points

Question Among a cohort of US frontline and essential workers infected with the original strain or the Delta or Omicron variants of SARS-CoV-2, is there a difference in COVID-19 symptoms or viral RNA load among those receiving mRNA vaccines compared with being unvaccinated?
Findings In this prospective cohort study that included 1199 participants with SARS-CoV-2 infection, receipt of 2 or 3 mRNA vaccine doses before Delta infections and 3 mRNA vaccine doses before Omicron infections was significantly associated with milder COVID-19 (less frequently symptomatic, febrile, or medically attended or shorter duration of illness) compared with being unvaccinated. Receipt of 2 mRNA vaccine doses 14 to 149 days prior to either Delta or Omicron infection was significantly associated with lower viral RNA load.
Meaning Among a cohort of US frontline and essential workers, recent vaccination with 2 or 3 mRNA vaccine doses, compared with being unvaccinated, was associated with attenuated COVID-19 symptoms and lower viral RNA load for Delta and Omicron variants of SARS-CoV-2 in some comparisons.

Abstract

Importance Data on the epidemiology of mild to moderately severe COVID-19 are needed to inform public health guidance.
Objective To evaluate associations between 2 or 3 doses of mRNA COVID-19 vaccine and attenuation of symptoms and viral RNA load across SARS-CoV-2 viral lineages.
Design, Setting, and Participants A prospective cohort study of essential and frontline workers in Arizona, Florida, Minnesota, Oregon, Texas, and Utah with COVID-19 infection confirmed by reverse transcriptase–polymerase chain reaction testing and lineage classified by whole genome sequencing of specimens self-collected weekly and at COVID-19 illness symptom onset. This analysis was conducted among 1199 participants with SARS-CoV-2 from December 14, 2020, to April 19, 2022, with follow-up until May 9, 2022, reported.
Exposures SARS-CoV-2 lineage (origin strain, Delta variant, Omicron variant) and COVID-19 vaccination status.
Main Outcomes and Measures Clinical outcomes included presence of symptoms, specific symptoms (including fever or chills), illness duration, and medical care seeking. Virologic outcomes included viral load by quantitative reverse transcriptase–polymerase chain reaction testing along with viral viability.
Results Among 1199 participants with COVID-19 infection (714 [59.5%] women; median age, 41 years), 14.0% were infected with the origin strain, 24.0% with the Delta variant, and 62.0% with the Omicron variant. Participants vaccinated with the second vaccine dose 14 to 149 days before Delta infection were significantly less likely to be symptomatic compared with unvaccinated participants (21/27 [77.8%] vs 74/77 [96.1%]; OR, 0.13 [95% CI, 0-0.6]) and, when symptomatic, those vaccinated with the third dose 7 to 149 days before infection were significantly less likely to report fever or chills (5/13 [38.5%] vs 62/73 [84.9%]; OR, 0.07 [95% CI, 0.0-0.3]) and reported significantly fewer days of symptoms (10.2 vs 16.4; difference, -6.1 [95% CI, -11.8 to -0.4] days). Among those with Omicron infection, the risk of symptomatic infection did not differ significantly for the 2-dose vaccination status vs unvaccinated status and was significantly higher for the 3-dose recipients vs those who were unvaccinated (327/370 [88.4%] vs 85/107 [79.4%]; OR, 2.0 [95% CI, 1.1-3.5]). Among symptomatic Omicron infections, those vaccinated with the third dose 7 to 149 days before infection compared with those who were unvaccinated were significantly less likely to report fever or chills (160/311 [51.5%] vs 64/81 [79.0%]; OR, 0.25 [95% CI, 0.1-0.5]) or seek medical care (45/308 [14.6%] vs 20/81 [24.7%]; OR, 0.45 [95% CI, 0.2-0.9]). Participants with Delta and Omicron infections who received the second dose 14 to 149 days before infection had a significantly lower mean viral load compared with unvaccinated participants (3 vs 4.1 log10 copies/?L; difference, -1.0 [95% CI, -1.7 to -0.2] for Delta and 2.8 vs 3.5 log10 copies/?L, difference, -1.0 [95% CI, -1.7 to -0.3] for Omicron).
Conclusions and Relevance In a cohort of US essential and frontline workers with SARS-CoV-2 infections, recent vaccination with 2 or 3 mRNA vaccine doses less than 150 days before infection with Delta or Omicron variants, compared with being unvaccinated, was associated with attenuated symptoms, duration of illness, medical care seeking, or viral load for some comparisons, although the precision and statistical significance of specific estimates varied.


Educational Objective
To identify the key insights or developments described in this article


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