COVID-19 vaccine effectiveness against hospitalizations in Paraguay, May 2021-April 2022: A test-negative design

Sandra Irala; Sarah Hamid; Elena Penayo; Fabiana Michel; Paula Couto; Cynthia Vazquez; María José Ortega; Chavely Domínguez; Silvia Battaglia; Marta Von Horoch; Romeo Montoya; Guillermo Sequera; Francisco Nogareda

doi:10.1016/j.vaccine.2023.09.015

COVID-19 vaccine effectiveness against hospitalizations in Paraguay, May 2021-April 2022: A test-negative design

Vaccine. 2023 Oct 13;41(43):6453-6460. doi: 10.1016/j.vaccine.2023.09.015. Epub 2023 Sep 15.

Authors

Affiliations

¹ Directorate General for Health Surveillance, Ministry of Public Health and Social Welfare, Paraguay.
² National Center for Immunization and Respiratory Diseases, US Centers for Disease Control and Prevention, Atlanta, GA, USA; Epidemic Intelligence Service, US Centers for Disease Control and Prevention, Atlanta, GA, USA. Electronic address: tsl4@cdc.gov.
³ Directorate General for Health Surveillance, Ministry of Public Health and Social Welfare, Paraguay. Electronic address: umedgvspy@gmail.com.
⁴ Pan American Health Organization, Asunción, Paraguay.
⁵ Pan American Health Organization, Washington, DC, USA.
⁶ Department of Virology, Central Laboratory for Public Health, Asunción, Paraguay.
⁷ National Program for Vaccine Preventable Diseases and Expanded Program on Immunization, Asunción, Paraguay.

PMID: 37716830
DOI: 10.1016/j.vaccine.2023.09.015

Abstract

Background: Vaccine effectiveness (VE) estimates vary by population characteristics and circulating variants. North America and Europe have generated many COVID-19 VE estimates but relied heavily on mRNA vaccines. Fewer estimates are available for non-mRNA vaccines and from Latin America. We aimed to estimate the effectiveness of several COVID-19 vaccines in preventing SARS-CoV-2-associated severe acute respiratory infection (SARI) in Paraguay from May 2021 to April 2022.

Methods: Using sentinel surveillance data from four hospitals in Paraguay, we conducted a test-negative case-control study to estimate COVID-19 vaccine effectiveness against SARI by vaccine type/brand and period of SARS-CoV-2 variant predominance (Gamma, Delta, Omicron). We used multivariable logistic regression adjusting for month of symptom onset, age group, and presence of ≥1 comorbidity to estimate the odds of COVID-19 vaccination in SARS-CoV-2 test-positive SARI case-patients compared to SARS-CoV-2 test-negative SARI control-patients.

Results: Of 4,229 SARI patients, 2,381 (56%) were SARS-CoV-2-positive case-patients and 1,848 (44%) were SARS-CoV-2-negative control-patients. A greater proportion of case-patients (73%; 95% CI: 71-75) than of control-patients (40%; 95% CI: 38-42) were unvaccinated. During the Gamma variant-predominant period, VE estimates for partial vaccination with mRNA vaccines and Oxford/AstraZeneca Vaxzevria were 90.4% (95% CI: 66.4-97.6) and 52.2% (95% CI: 25.0-69.0), respectively. During the Delta variant-predominant period, VE estimates for complete vaccination with mRNA vaccines, Oxford/AstraZeneca Vaxzevria, or Gamaleya Sputnik V were 90.4% (95% CI: 74.3-97.3), 83.2% (95% CI: 67.8-91.9), and 82.9% (95% CI: 53.0-95.2), respectively. The effectiveness of all vaccines declined substantially during the Omicron variant-predominant period.

Conclusions: This study contributes to our understanding of COVID-19 VE in Latin America and to global understanding of vaccines that have not been widely used in North America and Europe. VE estimates from Paraguay can parameterize models to estimate the impact of the national COVID-19 vaccination campaign in Paraguay and similar settings.

Keywords: COVID-19; Paraguay; Vaccination; Vaccine effectiveness.