Change in covid-19 risk over time following vaccination with CoronaVac: test negative case-control study
This article has been Reviewed by the following groups
Listed in
- Evaluated articles (ScreenIT)
Abstract
Objective
To 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.
Design
Test negative case-control study.
Setting
Community testing for covid-19 in São Paulo State, Brazil.
Participants
Adults 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 measures
RT-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.
Results
From 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.
Conclusions
Significant 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.
Article activity feed
-
-
SciScore for 10.1101/2021.12.23.21268335: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: The study was approved by the Ethical Committee for Research of Federal University of Mato Grosso do Sul (CAAE: 43289221.5.0000.0021). Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
No key resources detected.
Results from OddPub: Thank you for sharing your code.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:There are several limitations of this study. We did not have data on the variant of concern for each case included in the study. Therefore, some of the waning observed may be due to decreased effectiveness of CoronaVac against Delta …
SciScore for 10.1101/2021.12.23.21268335: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: The study was approved by the Ethical Committee for Research of Federal University of Mato Grosso do Sul (CAAE: 43289221.5.0000.0021). Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
No key resources detected.
Results from OddPub: Thank you for sharing your code.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:There are several limitations of this study. We did not have data on the variant of concern for each case included in the study. Therefore, some of the waning observed may be due to decreased effectiveness of CoronaVac against Delta compared to Gamma. This design is less affected by this issue than a design that estimates vaccine effectiveness over calendar time, but nonetheless, later calendar times are over-represented in later times since vaccination. By design, we did not estimate vaccine effectiveness, which would require a comparison with unvaccinated individuals, but rather change in odds of disease post-vaccination relative to a period shortly after the second dose. Therefore, we are unable to provide estimates of vaccine effectiveness after six months. In our analysis of hospitalisation or death, changing hospitalisation triage criteria over time and different thresholds for hospitalisation among vaccinated patients may have contributed to our estimates of waning. Our sensitivity analyses suggested bias but were unable to fully correct for it. For example, we offer an alternative explanation for observed early waning in HCWs, namely that early adopters were at higher COVID-19 risk. However, waning of humoral immune response has been observed on this timescale (ref Saure), so the extent to which increased SARS-CoV-2 infection risk among early vaccines contributes to apparent waning remains unclear. Finally, even within non-HCWs, CoronaVac was only available to certain...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
-
