Reduced Odds of Severe Acute Respiratory Syndrome Coronavirus 2 Reinfection After Vaccination Among New York City Adults, July 2021–November 2021
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Abstract
Background
Belief that vaccination is not needed for individuals with prior infection contributes to coronavirus disease 2019 (COVID-19) vaccine hesitancy. Among individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) before vaccines became available, we determined whether vaccinated individuals had reduced odds of reinfection.
Methods
We conducted a case-control study among adult New York City residents who tested positive for SARS-CoV-2 infection in 2020 and had not died or tested positive again >90 days after an initial positive test as of 1 July 2021. Case patients with reinfection during July 2021–November 2021 and controls with no reinfection were matched (1:3) on age, sex, timing of initial positive test in 2020, and neighborhood poverty level. Matched odds ratios (mORs) and 95% confidence intervals (CIs) were calculated using conditional logistic regression.
Results
Of 349 827 eligible adults, 2583 were reinfected during July 2021–November 2021. Of 2401 with complete matching criteria data, 1102 (45.9%) were known to be symptomatic for COVID-19-like illness, and 96 (4.0%) were hospitalized. Unvaccinated individuals, compared with individuals fully vaccinated within the prior 90 days, had elevated odds of reinfection (mOR, 3.21; 95% CI, 2.70 to 3.82), of symptomatic reinfection (mOR, 2.97; 95% CI, 2.31 to 3.83), and of reinfection with hospitalization (mOR, 2.09; 95% CI, .91 to 4.79).
Conclusions
Vaccination reduced odds of reinfections when the Delta variant predominated. Further studies should assess risk of severe outcomes among reinfected persons as new variants emerge, infection- and vaccine-induced immunity wanes, and booster doses are administered.
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SciScore for 10.1101/2021.12.09.21267203: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: This work was deemed public health surveillance that is non-research by the DOHMH Institutional Review Board. Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
Software and Algorithms Sentences Resources Statistical analyses were performed using SAS Enterprise Guide, version 7.1 (SAS Institute). SAS Institutesuggested: (Statistical Analysis System, RRID:SCR_008567)Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing …SciScore for 10.1101/2021.12.09.21267203: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: This work was deemed public health surveillance that is non-research by the DOHMH Institutional Review Board. Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
Software and Algorithms Sentences Resources Statistical analyses were performed using SAS Enterprise Guide, version 7.1 (SAS Institute). SAS Institutesuggested: (Statistical Analysis System, RRID:SCR_008567)Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:There are at least four limitations to this study. First, persons who were infected with SARS-CoV-2 in 2020 but who were not tested (e.g., due to limited testing availability) could not be included. Thus, our analysis of 1,048 first reinfections during June 15–August 31, 2021 among those initially infected in 2020 is an undercount, reducing sample size and precision of estimates. Because symptom status was missing for a quarter of reinfected individuals, the number of symptomatic reinfections was also an undercount. Further, our study population was likely biased toward those with more severe illnesses from initial infection (i.e., those who were hospitalized and thus eligible to access testing during the first wave of infections), which might have resulted in a population with stronger infection-induced immunity [26]. Second, some NYC residents were more likely to be repeatedly tested (e.g., as an occupational requirement particularly if unvaccinated), increasing the probability of ascertaining mild initial infections and/or reinfections. Further, if vaccinated persons were less likely to be tested, then given disproportionate ascertainment of reinfections among unvaccinated persons, VE could be overestimated. However, by assessing VE for symptomatic reinfection and for reinfection with hospitalization, we reduced this potential ascertainment bias from discretionary testing for non-clinical reasons. Third, exposure misclassification is possible because persons vaccinated out...
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.
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