Population-Level Effectiveness of an Inactivated Whole-Virion COVID-19 Vaccine: A Test Negative Case-Control Study in the Dominican Republic
Authors: Pérez-Then Eddy , Miric Marija , Qian Han-Zhu , Chen Ying Qing , Wang Yixin , Vallejo Virginia , Quezada Wanda , Flaquer Melissa , Olivo Juan , Castillo Jean , García Natalia , Calderón Katherine , Cueto Scarlet , Veras Bienvenido , Russo Miguel , Jiménez Indira , Guzmán Sorileydi , Garabito Luz , Cueto Evelyn , Colombo Fátima , Taveras Dominga , Torres Dania , Baez Jeannette , Yunen Jose , Koenig Ellen , Pérez Eladio , López Oscar , Severino Medina Fior Estephanie , Wang Xuanyi , Shao Yiming , Vermund Sten H ,   the DR Vaccine Study Team, Díaz Gladisger , Severino Faely Almonte , Acevedo Adalberto , Luciano Jesús A Vásquez , Cuello Joe M , Acevedo Indiana , Espinál Manuel Arturo Rosario , Martínez Cristobalina Ramírez , Díaz Deivy Antonio Peña , Espinál Dianelva Aquino , Almonte Domingo Antonio , Rodríguez Jairy Antonio Peguero , Rosa José Alberto Rosa , Reyes José Eduardo , Fernández José Joaquín Madera , Mercado Mayorix De Jesús Marte , Carmona Rosanna Carmelina De Los Santos , Liriano Ruth , Heyliger Alba Verónica , Mejía Alejandro Alberto Báez , Turbis Alexy , Aquino Cristiano , José Ezequiel Estrella , Rosario Yunior Manuel Ozuna Del , Rosario Carlina Estefany Mejía , Hermón Johanny Francheska Martínez , Colón Anniely , Flores Aura , Díaz Carmen , Rodríguez Delia , Estrella Johanna , Colón Jorge , Reyes Juan , Gil Lucero , Abbott Malú , Mota Mélery de , Polanco Nicolás , Jiménez Indira , Santana Reynira , Herrera Sabiel Ramírez , Castellanos Adilsa , Germosén Astrid , Fajardo Franllirda , Mercedes Kadishia , Méndez Mariel García , Cuevas F Saira , Sánchez Tomasa , Payano Ykaira , Gómez Yolenny , Mejía Ysaura Estefani Rosario , Sánchez Diego , Infante Hever , Grullón María , Lemos Yohanna , Carpio Pedro , Pineda Cristina Martínez , Núñez Manuel , Espiritusanto Diomary Rojas , Álvarez Gabriela , Nina Gissel Esperanza Puente , Cabrera Kelin Migdalia Norman , Guerrero Ramón Alberto , Mejía Bethania , Nicolás Kenia M , Guante Margarita , Lebrón Madelyn , Bidó Mallelin , Monción María , Brito Enrique Jiménez , Rosado Suleica , apoyo Personal de , Sosa Alba Sugilio de , Pimentel Barbarita , Feliciano Doris , Santos Laura de los , Morillo María , Mateo Petter Dipiton , Cruz Ramona de la , García María de los Ángeles , Tavárez Yudelka Polanco , Luna Rosa A Lugo , Castillo Ysabel , Ulloa Erika Linet Hernández , Pérez Evelyn Solange Báez 
Published: February 2023

Background

A continuing nationwide vaccination campaign began in the Dominican Republic on February 16, 2021 to prevent severe consequences of acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Estimates of vaccine effectiveness under real-world conditions are needed to support policy decision making and inform further vaccine selection.

Methods

We conducted a test-negative case-control study to assess the real-world effectiveness of nationwide coronavirus disease 2019 (COVID-19) vaccination program using an inactivated vaccine (CoronaVac) on preventing symptomatic SARS-CoV-2 infections and hospitalizations from August to November 2021 in the Dominican Republic. Participants were recruited from 10 hospitals in 5 provinces to estimate the effectiveness of full immunization (≥14 days after receipt of the second dose) and partial immunization (otherwise with at least 1 dose ≥14 days after receipt of the first dose).

Results

Of 1078 adult participants seeking medical care for COVID-19-related symptoms, 395 (36.6%) had positive polymerase chain reaction (PCR) tests for SARS-CoV-2; 142 (13.2%) were hospitalized during 15 days of follow up, including 91 (23%) among 395 PCR-positive and 51 (7.5%) among 683 PCR-negative participants. Full vaccination was associated with 31% lower odds of symptomatic infection (odds ratio [OR], 0.69; 95% confidence interval [CI], 0.52–0.93) and partial vaccination was associated with 49% lower odds (OR, 0.51; CI, 0.30–0.86). Among 395 PCR-positive participants, full vaccination reduced the odds of COVID-19-related hospitalization by 85% (OR, 0.15; 95% CI, 0.08–0.25) and partial vaccination reduced it by 75% (OR, 0.25; 95% CI, 0.08–0.80); full vaccination was associated with reduced use of assisted ventilation by 73% (OR, 0.27; 95% CI, 0.15–0.49).

Conclusions

Given the ancestral and delta viral variants circulating during this study period, our results suggest that the inactivated COVID-19 vaccine offered moderate protection against symptomatic SARS-CoV-2 infections and high protection against COVID-19-related hospitalizations and assisted ventilation. This is reassuring given that, as of August 2022, an estimated 2.6 billion inactivated CoronaVac vaccine doses had been administered worldwide. This vaccine will become a basis for developing multivalent vaccine against the currently circulating omicron variant.