Effectiveness of a bivalent mRNA vaccine dose against symptomatic SARS-CoV-2 infection among U.S. Healthcare personnel, September 2022–May 2023
Creators: name: Plumb, Ian D.
name: Briggs Hagen, Melissa
name: Wiegand, Ryan
name: Dumyati, Ghinwa
name: Myers, Christopher
name: Harland, Karisa K.
name: Krishnadasan, Anusha
name: James Gist, Jade
name: Abedi, Glen
name: Fleming-Dutra, Katherine E.
name: Chea, Nora
name: Lee, Jane E.
name: Kellogg, Melissa
name: Edmundson, Alexandra
name: Britton, Amber
name: Wilson, Lucy
name: Lovett, Sara A.
name: Ocampo, Valerie
name: Markus, Tiffanie M.
name: Smithline, Howard A.
name: Hou, Peter C.
name: Lee, Lilly C.
name: Mower, William
name: Rwamwejo, Fernand
name: Steele, Mark T.
name: Lim, Stephen C.
name: Schrading, Walter A.
name: Chinnock, Brian
name: Beiser, David G.
name: Faine, Brett
name: Haran, John P.
name: Nandi, Utsav
name: Chipman, Anne K.
name: LoVecchio, Frank
name: Eucker, Stephanie
name: Femling, Jon
name: Fuller, Matthew
name: Rothman, Richard E.
name: Curlin, Marcel E.
name: Talan, David A.
name: Mohr, Nicholas M.
Publisher: name: Elsevier
Year: 2024
Subjects: Bivalent
COVID-19
COVID-19 vaccines
Healthcare personnel
mRNA vaccines
SARS-CoV-2
Vaccine effectiveness

description: Background Bivalent mRNA vaccines were recommended since September 2022. However, coverage with a recent vaccine dose has been limited, and there are few robust estimates of bivalent VE against symptomatic SARS-CoV-2 infection (COVID-19). We estimated VE of a bivalent mRNA vaccine dose against COVID-19 among eligible U.S. healthcare personnel who had previously received monovalent mRNA vaccine doses.MethodsWe conducted a case-control study in 22 U.S. states, and enrolled healthcare personnel with COVID-19 (case-participants) or without COVID-19 (control-participants) during September 2022–May 2023. Participants were considered eligible for a bivalent mRNA dose if they had received 2–4 monovalent (ancestral-strain) mRNA vaccine doses, and were ?67 days after the most recent vaccine dose. We estimated VE of a bivalent mRNA dose using conditional logistic regression, accounting for matching by region and four-week calendar period. We adjusted estimates for age group, sex, race and ethnicity, educational level, underlying health conditions, community COVID-19 exposure, prior SARS-CoV-2 infection, and days since the last monovalent mRNA dose.ResultsAmong 3,647 healthcare personnel, 1,528 were included as case-participants and 2,119 as control-participants. Participants received their last monovalent mRNA dose a median of 404 days previously; 1,234 (33.8%) also received a bivalent mRNA dose a median of 93 days previously. Overall, VE of a bivalent dose was 34.1% (95% CI, 22.6%–43.9%) against COVID-19 and was similar by product, days since last monovalent dose, number of prior doses, age group, and presence of underlying health conditions. However, VE declined from 54.8% (95% CI, 40.7%–65.6%) after 7–59 days to 21.6% (95% CI 5.6%–34.9%) after ?60 days.ConclusionsBivalent mRNA COVID-19 vaccines initially conferred approximately 55% protection against COVID-19 among U.S. healthcare personnel. However, protection waned after two months. These findings indicate moderate initial protection against symptomatic SARS-CoV-2 infection by remaining up-to-date with COVID-19 vaccines.