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. 2023 Feb 8;76(3):e360-e366.
doi: 10.1093/cid/ciac430.

Effectiveness of Heterologous Coronavirus Disease 2019 (COVID-19) Vaccine Booster Dosing in Brazilian Healthcare Workers, 2021

Alexandre R Marra  1   2 , João Luiz Miraglia  1 , Daniel Tavares Malheiros  1 , Yang Guozhang  1 , Vanessa Damazio Teich  1 , Elivane da Silva Victor  1 , João Renato Rebello Pinho  1 , Adriana Cypriano  1 , Laura Wanderly Vieira  1 , Miria Polonio  1 , Rafael Herrera Ornelas  1 , Solange Miranda de Oliveira  1 , Flavio Araujo Borges Junior  1 , Silvia Cristina Cassiano Oler  1 , Guilherme de Paula Pinto Schettino  1 , Ketti Gleyzer de Oliveira  1 , Rúbia Anita Ferraz Santana  1 , Fernanda de Mello Malta  1 , Deyvid Amgarten  1 , Ana Laura Boechat  1 , Noelly Maria Zimpel Trecenti  1 , Takaaki Kobayashi  2 , Jorge L Salinas  3 , Michael B Edmond  4 , Luiz Vicente Rizzo  1
Affiliations

Effectiveness of Heterologous Coronavirus Disease 2019 (COVID-19) Vaccine Booster Dosing in Brazilian Healthcare Workers, 2021

Alexandre R Marra et al. Clin Infect Dis. .

Abstract

Background: Little is currently known about vaccine effectiveness (VE) for either 2 doses of Oxford-AstraZeneca (ChAdOx1) viral vector vaccine or CoronaVac (Instituto Butantan) inactivated viral vaccine followed by a third dose of mRNA vaccine (Pfizer/BioNTech) among healthcare workers (HCWs).

Methods: We conducted a retrospective cohort study among HCWs (aged ≥18 years) working in a private healthcare system in Brazil from January to December 2021. VE was defined as 1 - incidence rate ratio (IRR), with IRR determined using Poisson models with the occurrence of laboratory-confirmed coronavirus disease 2019 (COVID-19) infection as the outcome, adjusting for age, sex, and job type. We compared those receiving viral vector or inactivated viral primary series (2 doses) with those who received an mRNA booster.

Results: A total of 11 427 HCWs met the inclusion criteria. COVID-19 was confirmed in 31.5% of HCWs receiving 2 doses of CoronaVac vaccine versus 0.9% of HCWs receiving 2 doses of CoronaVac vaccine with mRNA booster (P < .001) and 9.8% of HCWs receiving 2 doses of ChAdOx1 vaccine versus 1% among HCWs receiving 2 doses of ChAdOx1 vaccine with mRNA booster (P < .001). In the adjusted analyses, the estimated VE was 92.0% for 2 CoronaVac vaccines plus mRNA booster and 60.2% for 2 ChAdOx1 vaccines plus mRNA booster, when compared with those with no mRNA booster. Of 246 samples screened for mutations, 191 (77.6%) were Delta variants.

Conclusions: While 2 doses of ChAdOx1 or CoronaVac vaccines prevent COVID-19, the addition of a Pfizer/BioNTech booster provided significantly more protection.

Keywords: COVID-19 vaccine; CoronaVac; Oxford-AstraZeneca; Pfizer/BioNTech booster; effectiveness.

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Conflict of interest statement

Potential conflicts of interest. A. L. B. reports the following contracts or grants unrelated to this work: MCTIC/CNPq/FNDCT/MS/SCTIE/Decit 07/2020, Brazil. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

Figures

Figure 1.
Figure 1.
Cumulative incidence of COVID-19 infection (by RT-PCR) among HCWs vaccinated with 2 doses of CoronaVac (left) or Oxford-AstraZeneca (ChAdOx1) (right), with and without a third (booster) dose with mRNA (Pfizer/BioNTech) vaccine. Abbreviations: COVID-19, coronavirus disease 2019; HCW, healthcare worker; RT-PCR, reverse transcription–polymerase chain reaction.
See this image and copyright information in PMC

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