Journal Article

Change in covid-19 risk over time following vaccination with CoronaVac: test negative case-control study

de Paula, Regiane Cardoso, de Moura Villela, Edlaine Faria, Hitchings, Matt D T, Cummings, Derek A T, Dean, Natalie E, Croda, Julio, Andrews, Jason R, de Oliveira, Silvano Barbosa, Ranzani, Otavio T, Scaramuzzini Torres, Mario Sergio, de Oliveira, Roberto Dias, Lind, Margaret L, de Paula, Olivia Ferreira Pereira, Schulz, Wade, D’Agostini, Tatiana Lang, Gorinchteyn, Jean Carlo, Almiron, Maria, Said, Rodrigo, de Araújo, Wildo Navegantes, Vieira da Silva, Patricia, Ko, Albert I, Dorion, Murilo

2022

Overview

AbstractObjectiveTo estimate the change in odds of covid-19 over time following primary series completion of the inactivated whole virus vaccine CoronaVac (Sinovac Biotech) in São Paulo State, Brazil.DesignTest negative case-control study.SettingCommunity testing for covid-19 in São Paulo State, Brazil.ParticipantsAdults aged ≥18 years who were residents of São Paulo state, had received two doses of CoronaVac, did not have a laboratory confirmed SARS-CoV-2 infection before vaccination, and underwent reverse transcription polymerase chain reaction (RT-PCR) testing for SARS-CoV-2 from 17 January to 14 December 2021. Cases were matched to test negative controls by age (in 5 year bands), municipality of residence, healthcare worker status, and epidemiological week of RT-PCR test.Main outcome measuresRT-PCR confirmed symptomatic covid-19 and associated hospital admissions and deaths. Conditional logistic regression was adjusted for sex, number of covid-19 associated comorbidities, race, and previous acute respiratory illness.ResultsFrom 202 741 eligible people, 52 170 cases with symptomatic covid-19 and 69 115 test negative controls with covid-19 symptoms were formed into 43 257 matched sets. Adjusted odds ratios of symptomatic covid-19 increased with time since completion of the vaccination series. The increase in odds was greater in younger people and among healthcare workers, although sensitivity analyses suggested that this was in part due to bias. In addition, the adjusted odds ratios of covid-19 related hospital admission or death significantly increased with time compared with the odds 14-41 days after series completion: from 1.25 (95% confidence interval 1.04 to 1.51) at 70-97 days up to 1.94 (1.41 to 2.67) from 182 days onwards.ConclusionsSignificant increases in the risk of moderate and severe covid-19 outcomes occurred three months after primary vaccination with CoronaVac among people aged 65 and older. These findings provide supportive evidence for the implementation of vaccine boosters in these populations who received this inactivated vaccine. Studies of waning should include analyses designed to uncover common biases.

• Publisher: British Medical Journal Publishing Group,BMJ Publishing Group LTD
• Subject: Adolescent / Adult / Age / Bias / Brazil - epidemiology / Case-Control Studies / Comorbidity / Coronaviruses / COVID-19 / COVID-19 - epidemiology / COVID-19 - prevention & control / COVID-19 Testing / COVID-19 Vaccines / Disease transmission / Epidemiology / Health care / Humans / Illnesses / Infections / Medical personnel / Patient admissions / Polymerase chain reaction / Population / Respiratory diseases / Reverse transcription / SARS-CoV-2 / Sensitivity analysis / Severe acute respiratory syndrome coronavirus 2 / Surveillance / Vaccination / Vaccines / Workers