Protection against Omicron from Vaccination and Previous Infection in a Prison System | NEJM - nejm.org

Evidence of the effectiveness of vaccines against terrible acute respiratory syndrome coronavirus 2 (SARS-CoV-2) comes mostly from studies of the archetypal strain and of variants that emerged earlier the B.1.1.529 (omicron) variant.^1-4 Previous corruption confers extortion against reinfection,^1,5 but some infection-acquired and vaccine-acquired extortion against corruption wane implicit time.^6-9

Recent studies bespeak that vaccinations person continued to beryllium effectual against hospitalization and death^10-13 but person had reduced effectiveness successful protecting against confirmed infection^11,14 and symptomatic illness^10,15,16 with omicron. In immoderate studies, estimates of hybrid immunity against corruption with omicron person been reported.^10,14 However, constricted accusation is disposable with respect to the level of extortion conferred by vaccine boosters and the timing of erstwhile infection.

We analyzed information from the California Department of Corrections and Rehabilitation (CDCR), which operates the 2nd largest authorities situation strategy successful the United States. Prisons and jails are particularly risky congregate settings for coronavirus illness 2019 (Covid-19), and galore ample outbreaks person occurred successful these settings during the pandemic.^1,17 The CDCR began offering a 3rd (booster) mRNA vaccine dose to residents and unit successful precocious August 2021; by the extremity of 2021, among persons successful the eligible population, 77.9% of residents and 40.3% of unit had been vaccinated with a booster.¹⁸ The omicron variant was archetypal identified wrong the CDCR strategy among assayed affirmative samples obtained from correctional unit connected December 10, 2021. Substantial outbreaks occurred soon thereafter among some residents and staff; these outbreaks were accordant with the timing of the worldwide question of omicron infection.

We evaluated confirmed SARS-CoV-2 infections among astir 60,000 incarcerated persons and 17,000 situation unit successful California during the omicron outbreak play utilizing information collected from December 24, 2021, done April 14, 2022. Our extremity was to estimation the levels of extortion conferred by mRNA vaccines against corruption according to some the fig of doses that persons had received and whether they had had a erstwhile documented corruption earlier the commencement of the reflection period. We besides estimated the effectiveness of a 3rd mRNA vaccine dose among the persons who had been eligible to person a booster.

Study Design and Population

We utilized a retrospective cohort survey design. The play of involvement was restricted to outbreak phases that occurred astatine each of the 35 prisons successful the CDCR strategy betwixt December 24, 2021 (approximately 2 weeks aft the omicron variant was initially identified wrong the situation system), and April 14, 2022. The CDCR considered a situation to beryllium successful an outbreak signifier if 3 of much related cases among residents were detected wrong a 14-day play astatine the prison. During the outbreak phases, the prisons implemented modified operations, programs, and services for residents and mandatory investigating for unit to minimize the hazard of ongoing Covid-19 transmission.^19,20 The SARS-CoV-2 infections that were detected successful the situation strategy and successful the wide colonisation successful California during this 16-week play were dominated by the omicron variant.²¹ Our survey analyzed 2 high-risk populations: residents and correctional unit astatine these prisons.

Residents were eligible for inclusion successful the survey cohort if they were incarcerated astatine the commencement of the outbreak signifier astatine their prison. To absorption connected correctional workers who had the highest hazard of workplace exposure, unit were eligible for inclusion if they worked successful custody oregon wellness attraction positions (excluding declaration employees), if they had regular nonstop interaction with residents, if they had worked during the archetypal week of the outbreak signifier astatine their prison, and if they had worked astatine slightest fractional the fig of days betwixt the commencement of an outbreak and their information censoring date. In addition, to trim the imaginable for misclassification of erstwhile corruption and vaccination status, we restricted our survey cohort to residents who were incarcerated successful a CDCR situation earlier January 1, 2021, and unit who were employed earlier January 1, 2021, and had worked consistently during 2021 (details are provided successful the Supplementary Appendix, disposable with the afloat substance of this nonfiction astatine NEJM.org).

Next, residents and unit who met the supra criteria were excluded if they had received the adenovirus vector–based vaccine Ad26.COV2.S (Johnson & Johnson–Janssen), if they had received lone 1 mRNA vaccine dose, if they had received an chartless vaccine oregon a vaccine that was not approved oregon authorized by the Food and Drug Administration, if they had inconsistencies regarding vaccination dates, if they had off-schedule vaccination,²² if they had incomplete demographic data, oregon if the situation wherever they were housed oregon wherever they worked was not known. To debar imaginable misclassification of reinfections, we excluded persons who had had a caller SARS-CoV-2 corruption (i.e., persons who had had an corruption that was archetypal detected ≤90 days earlier the commencement of the outbreak signifier astatine their situation oregon persons who continued to trial affirmative ≤30 days earlier the commencement of the outbreak phase). The reflection clip began connected the commencement day of the outbreak and ended connected the earliest of the pursuing clip points: the time that the illustration from a affirmative trial was obtained, the time earlier caller vaccination, oregon the time earlier transportation (for residents) oregon a work-shift alteration (for staff) to a antithetic prison.

Data Collection and Key Measures

CDCR collects and stores deidentified information connected each residents and unit connected a regular basis. For residents, elaborate accusation from reverse-transcriptase–polymerase-chain-reaction (RT-PCR) and antigen SARS-CoV-2 investigating came from a multilayered, voluntary investigating programme (in which 99.9% of the tests performed were RT-PCR assays) that included risk-based regular testing, surveillance testing, and investigating successful effect to detected outbreaks (see Table S1 successful the Supplementary Appendix). During outbreaks, each unit were tested astatine slightest erstwhile play done a mandatory RT-PCR investigating program, and unit who worked successful situation wellness attraction facilities were tested astatine slightest doubly weekly.²³ All unit could acquisition investigating voluntarily, and adjacent contacts with progressive cases triggered a compulsory test.²⁴ By January 1, 2022, much than fractional the prisons had entered an outbreak phase, with the signifier of the past situation commencing connected January 18, 2022.

All tests and vaccinations that were administered by oregon reported to the CDCR since March 2020 were utilized to deduce each person’s erstwhile corruption presumption and vaccination status. We defined a erstwhile SARS-CoV-2 corruption by the beingness of astatine slightest 1 affirmative trial successful the CDCR records earlier the commencement of the reflection period. Previous infections were categorized according to whether they occurred earlier July 1, 2021, which reflected the play earlier the emergence of the B.1.617.2 (delta) variant, oregon whether they occurred connected oregon aft July 1, 2021, which corresponded to the play of precocious prevalence of the delta variant.^1,21 Persons infected during some periods were assigned to the second period.

In summation to elaborate accusation connected investigating and vaccination (e.g., dates and vaccine brand), the survey information included demographic characteristics of the cohort members (sex oregon sex identity, age, and contention oregon taste group), carceral characteristics of the residents (prison, country type, and information level), and carceral characteristics of the unit (prison and benignant of position). For residents, a documented past of 17 imaginable coexisting conditions (e.g., hypertension, chronic kidney disease, and asthma) and a composite hazard people designed by the CDCR to people the hazard of terrible unwellness from SARS-CoV-2 corruption (see Table S2) were provided. Risk scores were top-coded to a people of 2 successful accordance with the CDCR explanation of residents astatine mean to precocious risk. Residents with scores of 2 oregon higher were younger than 65 years of property with coexisting conditions oregon were 65 years of property oregon older. This hazard people was utilized to usher Covid-19 mitigation policies, including those involving vaccination, testing, and housing. Information connected terrible outcomes of corruption (i.e., hospitalization and death) was disposable lone for residents.

Study Oversight

The survey was approved by the organization reappraisal committee astatine Stanford University. Results are reported successful accordance with STROBE (Strengthening the Reporting of Observational Studies successful Epidemiology) guidelines²⁵; a checklist of STROBE recommendations is provided successful the Supplementary Appendix. The authors vouch for the accuracy and completeness of the data.

Statistical Analysis

The extremity of our investigation was to estimation the effectiveness of vaccination and erstwhile corruption against omicron infection. In our superior analysis, we utilized multivariate Cox models to analyse the incidence of confirmed infections successful groups defined according to combinations of vaccination and erstwhile corruption histories during the applicable omicron outbreak phase. The models allowed the baseline hazard to alteration according to prison. We utilized inverse-probability weighting to trim the effects of confounding owed to differences successful baseline characteristics among cohort members. Covariate-balancing propensity scores²⁶ were calculated according to demographic, clinical, and carceral characteristics. Specifically, residents were weighted according to prison, Covid-19 hazard people (0, 1, oregon ≥2), country benignant (cell oregon dormitory), enactment (male oregon female), and property (as a continuous variable). Staff were weighted according to prison, presumption (custody oregon wellness care), property radical (18 to 39, 40 to 54, oregon ≥55 years), and sex individuality (man oregon woman); details are provided successful Section 3.1 successful the Supplementary Appendix. Stabilized weights were trimmed to trim instability and bias from utmost scores.²⁷

We estimated vaccine- and infection-acquired extortion with a acceptable of indicator variables that described combinations of vaccination and erstwhile corruption status. Effectiveness was expressed arsenic a percent simplification successful the hazard complaint of omicron corruption comparative to the radical that had not had erstwhile documented corruption oregon been vaccinated (measured arsenic 1 minus the hazard ratio). We besides repeated the analyses utilizing a modified acceptable of indicators to estimation the further effectiveness of 3 doses of vaccine arsenic compared with 2 doses. We calculated 95% assurance intervals utilizing modular errors clustered according to prison. Analyses were not adjusted for aggregate comparisons. We study the results for residents and unit separately.

The attack that was utilized successful our superior analysis, described above, enabled the estimation and examination of corruption risks crossed assorted strata that were defined according to combinations of vaccination and erstwhile corruption histories. However, we hypothesized that an alternate survey plan — a rolling matched-cohort design²⁸ — mightiness beryllium amended suited to controlling for imaginable confounding erstwhile estimating vaccine effectiveness wrong each previous-infection stratum. Instead of weighting vulnerability groups connected the ground of characteristics astatine the commencement of the omicron outbreak, arsenic successful our superior analysis, this alternate attack matched boosted persons with persons who had been eligible for a booster but had been vaccinated with lone 2 doses. Persons were matched connected the ground of erstwhile corruption presumption and different covariates applicable to vaccination according to the day that the boosted idiosyncratic was vaccinated with the 3rd dose. Details are provided successful Section 3.2 successful the Supplementary Appendix. In this secondary analysis, Cox models were utilized to estimation the relation betwixt vaccination presumption (two doses oregon 3 doses) and omicron corruption according to erstwhile corruption status. These models allowed the baseline hazard to alteration according to prison, with accommodation for calendar week.

We performed 5 sets of sensitivity analyses. In the archetypal set, we assessed the sensitivity of the results from our superior investigation to utmost weights by comparing estimates from a scope of analyses that varied the grade to which ample weights were trimmed downward. In the 2nd set, we modified the superior investigation to set for the benignant of mRNA vaccine (BNT162b2 [Pfizer–BioNTech], mRNA-1273 [Moderna], oregon both). In the 3rd set, we examined the sensitivity of estimates to our specification of reinfections by narrowing the exclusion criterion regarding caller infections, whereby the maximum fig of days betwixt the day that an corruption was archetypal detected and the commencement of the outbreak signifier was shortened from 90 days to 30 days. In the 4th set, fixed that our superior investigation included some persons who had been eligible for boosters and those who had not been eligible, we excluded tests from persons who had been vaccinated with 2 doses but were not yet eligible for a 3rd dose. In the 5th acceptable of sensitivity analyses, to measure the sensitivity of our propensity-score model, we expanded the acceptable of demographic and carceral characteristics that had antecedently been identified arsenic being predictive of vaccine acceptance among incarcerated persons and staff.^29,30

All the analyses were performed with the usage of R software, mentation 3.5.2 (R Foundation for Statistical Computing). Additional details regarding exemplary and adaptable specifications are provided successful the Supplementary Appendix.

Study Population

Table 1. Table 1. Population Counts and Weighted Characteristics of Residents and Staff astatine Baseline According to Previous Infection and Vaccination Status. Figure 1. Figure 1. Study Population.

The Ad26.COV2.S vaccine, an adenovirus vector–based vaccine, was developed by Johnson & Johnson–Janssen. The delta variant is besides known arsenic B.1.617.2.

Figure 2. Figure 2. Testing and Cases successful the Study Cohort.

The precocious graphs of Panels A and B amusement the regular numbers and percentages of residents and unit who underwent investigating for terrible acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and who had a affirmative trial result. There was reduced unit investigating connected national holidays. The little graphs of Panels A and B amusement the regular numbers of affirmative cases of coronavirus illness 2019 (Covid-19). Testing and lawsuit bid were extended implicit the humanities play that began 2.5 months earlier the commencement of the survey period.

The weighted characteristics of the survey colonisation astatine baseline are shown successful Table 1. Among 59,794 residents who met the inclusion criteria for the survey cohort, 16.7% tested affirmative during the survey period, and among 16,572 unit who met the inclusion criteria, 30.3% tested affirmative during the survey play (Figure 1 and Table S4). The persons who were included successful the survey cohort were broadly typical of the wide colonisation of residents who were incarcerated astatine immoderate constituent during the survey play and the wide colonisation of unit who worked astatine immoderate clip during the survey play (Table S3). The mean (±SD) fig of times per week that persons were tested was 0.6±0.6 among residents and 1.5±1.0 among unit (Figure 2 and Fig. S2). A full of 96 hospitalizations and 1 decease that were assessed arsenic being related to SARS-CoV-2 corruption were documented among residents. Data connected hospitalizations and deaths were not disposable for staff.

Figure 3. Figure 3. Vaccination and Previous Infection Status of the Study Cohort implicit Time.

The California Department of Corrections and Rehabilitation began their vaccination programme for the mRNA superior bid astatine the extremity of 2020 and began offering boosters astatine the extremity of August 2021. A precocious incidence of erstwhile corruption was detected successful the survey cohort during periods of precocious incidence of Covid-19 successful the wide colonisation successful California.

Nearly fractional the residents and 1 3rd of the unit had erstwhile confirmed infections, astir of which had occurred earlier the delta variant became the ascendant strain (Figure 3). Among residents, the median interval betwixt the commencement of their past corruption and the commencement of the outbreak signifier successful their situation was 393 days (interquartile range, 372 to 435); among staff, the median interval was 367 days (interquartile range, 163 to 400).

Among persons who had received 2 vaccine doses only, the median clip since receipt of the 2nd dose was 246 days (interquartile range, 127 to 294) for residents and 205 days (interquartile range, 90 to 324) for staff. Among those who had received 3 doses, the median clip since receipt of the 3rd dose was 35 days (interquartile range, 27 to 48) for residents and 37 days (interquartile range, 13 to 55) for staff.

Effectiveness of Vaccination and Previous Infection against Omicron Infection

Figure 4. Figure 4. Adjusted Estimates of Effectiveness of Vaccination and Previous Infection against Omicron Infection among Residents and Staff successful California State Prisons.

Shown are unadjusted lawsuit counts, full counts, and adjusted estimates of the effectiveness of vaccination and erstwhile corruption against omicron corruption outbreaks that occurred betwixt December 24, 2021, and April 14, 2022. Persons who had been vaccinated had received 2 oregon 3 doses of mRNA vaccines only. The reddish squares denote residents, and the bluish squares denote staff. 𝙸 bars denote 95% assurance intervals.

Within the nonmigratory population, the estimated effectiveness (measured arsenic 1 minus the hazard ratio) of vaccination against confirmed SARS-CoV-2 corruption during the play of omicron predominance among persons who had not had known erstwhile corruption was 18.6% (95% assurance interval [CI], 7.7 to 28.1) for those who had received lone 2 vaccine doses and 40.9% (95% CI, 31.9 to 48.7) for those who had received 3 doses (Figure 4). Among the residents who had not been vaccinated, the estimated infection-conferred effectiveness against corruption was 27.5% (95% CI, 14.8 to 38.4) among persons who had been infected earlier the play of delta predominance and 38.3% (95% CI, 6.5 to 59.3) among those who had been infected during the play of delta predominance. Among the residents who had been infected earlier the play of delta predominance, the estimated effectiveness of vaccination was 51.2% (95% CI, 41.5 to 59.2) with 2 vaccine doses and 57.7% (95% CI, 50.8 to 63.6) with 3 doses; among those infected during the play of delta predominance, the estimated effectiveness was 68.7% (95% CI, 38.5 to 84.1) and 84.6% (95% CI, 70.7 to 91.9), respectively.

Analyses of information from residents and unit produced estimates that indicated that the comparative levels of effectiveness from vaccination and erstwhile corruption were mostly accordant (Figure 4 and Table S5A). However, the estimated levels of effectiveness from vaccination among unit who had not had known erstwhile corruption were higher than those among residents without known erstwhile infection, with estimates of 40.1% (95% CI, 34.0 to 45.6) among unit who had received 2 vaccine doses and 72.1% (95% CI, 67.2 to 76.2) among those who had received 3 doses.

Among the unit who had not been vaccinated, the estimated effectiveness of corruption that had occurred earlier the play of delta predominance was 16.3% (95% CI, 8.1 to 23.7), and the estimated effectiveness of corruption that had occurred during the play of delta predominance was 48.9% (95% CI, 41.6 to 55.3). Among the unit who had been infected earlier the play of delta predominance, the estimated effectiveness of vaccination was 55.8% (95% CI, 49.6 to 61.2) with 2 doses and 77.6% (95% CI, 71.7 to 82.2) with 3 doses; among those infected during the play of delta predominance, the estimated effectiveness was 83.2% (95% CI, 77.7 to 87.4) and 87.9% (95% CI, 76.0 to 93.9), respectively.

Effectiveness of a Third Dose among Booster-Eligible Persons

In our superior analysis, extortion against corruption was estimated comparative to an idiosyncratic person’s presumption astatine the commencement of the outbreak phase, and the investigation included some persons who had been eligible to person a booster and those who had not been eligible to person a booster. In this analysis, the estimated effectiveness of a 3rd dose, arsenic compared with 2 doses, among residents who were eligible to person a booster was 27.4% (95% CI, 19.9 to 34.2) among those who had not had known erstwhile infection, 13.3% (95% CI, 3.2 to 22.3) among those who had been infected earlier the play of delta predominance, and 50.7% (95% CI, −42.0 to 82.9) among those who had been infected during the play of delta predominance. Among staff, the estimated effectiveness of a 3rd dose was 53.4% (95% CI, 46.7 to 59.3) among those who had not had known erstwhile infection, 49.2% (95% CI, 35.0 to 60.3) among those who had been infected earlier the play of delta predominance, and 28.0% (95% CI, −33.0 to 61.0) among those who had been infected during the play of delta predominance.

In our secondary analysis, successful which boosted persons were matched according to the day of vaccination with the 3rd dose with controls who had been eligible for a 3rd dose but had not received a 3rd dose, the estimated incremental effectiveness of the 3rd dose among residents was 25.0% (95% CI, 16.6 to 32.5) among those who had not had known erstwhile corruption and 46.4% (95% CI, 38.3 to 53.4) among those who had been infected earlier the play of delta predominance (Table S5B). Among staff, the estimated incremental effectiveness of the 3rd dose was 57.9% (95% CI, 48.4 to 65.7) among those who had not had known erstwhile corruption and 57.7% (95% CI, 46.2 to 66.7) among those who had been infected earlier the play of delta predominance. Incremental effectiveness could not beryllium estimated for persons infected during the play of delta predominance due to the fact that nary infections were documented among those who had received a 3rd dose.

Sensitivity Analyses

Estimates that were derived with the usage of untrimmed weights and weights with higher degrees of trimming were not appreciably antithetic from those of the superior analysis, nor were estimates that were derived from alternate exemplary specifications that were adjusted for the benignant of mRNA vaccine. Analyses of the expanded illustration that included much caller erstwhile infections produced somewhat higher estimates of effectiveness than those of the superior investigation among persons whose erstwhile corruption occurred during the play of delta predominance. When persons who had not been eligible for a 3rd dose were excluded, the estimates of effectiveness were somewhat little than those of the superior investigation among persons who had been vaccinated with 2 doses. Estimates that were derived with the usage of the propensity-score exemplary successful which an expanded acceptable of covariates was included produced estimates of effectiveness that were akin to those of the superior analysis. The results of the sensitivity analyses are provided successful Tables S5A, S5C, S5D, and S5E.

This survey involving 2 high-risk populations evaluated the effectiveness of 2 oregon 3 doses of BNT162b2 and mRNA-1273 vaccines, and of erstwhile corruption earlier and during the play of delta predominance, successful reducing the hazard of corruption with the SARS-CoV-2 omicron variant. Our findings adhd to the grounds basal for vaccine effectiveness and immunity conferred by erstwhile corruption by providing estimates of effectiveness that were circumstantial to antithetic combinations of vaccination and erstwhile corruption histories. These estimates were based connected 2 susceptible populations successful which reliable ascertainment of corruption during the survey play was likely, owing to precocious levels of testing.

Vaccination with 3 mRNA doses was associated with a reduced hazard of corruption with the omicron variant. Our estimates among persons who had not had known erstwhile corruption were akin to those of a convenience-sample survey of the effectiveness of 2 oregon 3 mRNA-1273 doses involving information from a wellness attraction strategy that serves confederate California.¹¹ A cohort survey that was conducted with the usage of information from a wellness attraction strategy that serves Connecticut did not amusement important further extortion from vaccination with a 3rd dose among persons with erstwhile infection.¹⁴ Our superior investigation included some persons who had been eligible to person a 3rd dose and those who had not been eligible to person a 3rd dose, an attack that perchance biased estimates of the effectiveness of a 3rd dose downward. The higher hazard of corruption among persons who had received 2 oregon less vaccine doses could person induced enactment bias if the astir susceptible persons had been infected during the play earlier omicron predominance, which would besides person biased estimates of effectiveness downward. As expected, the estimates of effectiveness were akin but somewhat higher successful the secondary investigation than successful the superior analysis; the secondary investigation utilized an alternate plan that astir apt corrected for these biases much efficaciously and provided estimates among persons who survived agelong capable to go eligible for a 3rd dose. However, the blimpish estimates from the superior analysis, arsenic good arsenic those from the secondary and sensitivity analyses, each bespeak substantial, further extortion from a 3rd mRNA dose against confirmed infection, irrespective of erstwhile corruption history. Our findings suggest that a 3rd dose is beneficial, adjacent successful persons with erstwhile confirmed infection.

The implicit levels of effectiveness against corruption successful our survey are substantially little than those estimated successful earlier studies^8,31-33 that were conducted earlier the omicron outbreaks occurred; furthermore, we observed that the estimated extortion conferred by erstwhile corruption varied substantially with respect to timing, with considerably little estimates among persons infected earlier the emergence of the delta variant. We estimated that vaccination augmented extortion among persons who had had erstwhile infection, a uncovering that is accordant with findings reported successful different studies.^11,14 Three doses of vaccine successful operation with erstwhile corruption resulted successful the highest estimates of effectiveness, and these levels approached those reported successful studies involving vaccination with the superior bid that were conducted earlier the occurrence of the omicron outbreaks.

For respective combinations of vulnerability history, the nonmigratory colonisation had little estimates of effectiveness than the unit population. Although the CDCR has implemented an extended investigating programme successful some populations, investigating among residents was neither regular nor compulsory. Undetected erstwhile infections could person contributed to dilution of the estimates of effectiveness among residents, arsenic could underascertainment of infections during the survey period. Staff besides person a greater quality to prosecute successful protective behaviors, specified arsenic masking and societal distancing, some astatine enactment and extracurricular of work. Staff who remained uninfected earlier the emergence of the omicron variant whitethorn bespeak a subpopulation that engages successful a higher grade of protective behavior; this concern could besides explicate immoderate of the differences betwixt colonisation estimates.

In this study, vaccine effectiveness was examined successful the discourse of accusation astir infection- and vaccine-acquired immunity against the omicron variant and accusation astir the timing of erstwhile infections. The survey has notable strengths. First, we utilized elaborate regular accusation regarding vaccination presumption and cardinal Covid-19 outcomes for each subordinate of the high-risk populations studied. These information allowed america to set for cardinal imaginable confounders, arsenic good arsenic for demographic and exposure-related characteristics. Second, the ample illustration sizes of the 2 chiseled populations enabled comparatively precocious precision successful our estimates, and the information that estimates of the comparative levels of effectiveness crossed the 2 populations were akin is notable contempt the differences betwixt the populations with respect to surviving situations, investigating programs, and demographic characteristics.

Our survey besides has respective limitations. Although a assortment of covariates — including those related to vaccine acceptance and the hazard of erstwhile corruption — were utilized to equilibrium baseline characteristics, residual confounding could remain. Vaccine uptake and the occurrence of erstwhile infections varied betwixt residents and staff. Differences successful corruption risks betwixt the 2 populations whitethorn successful portion bespeak analyzable interactions of vaccine and erstwhile corruption levels and timing. Furthermore, the CDCR conducted constricted viral sequencing and molecular testing, truthful we cannot disentangle the effects of variants from temporal waning, nor tin we corroborate that each cases that were observed during the survey play were omicron infections.

Distinct investigating programs and exposures for residents and unit during the survey play whitethorn besides person introduced confounding, though respective results supply reassurances. First, though unit investigating was inconsistent crossed vaccination and erstwhile corruption statuses, astir each unit were tested astatine slightest erstwhile play (range of means, 0.9 to 2.0 tests per week), which provided comparatively implicit lawsuit detection. Second, though investigating for residents was not routine, random, oregon compulsory, investigating was comparatively accordant crossed vaccination and erstwhile corruption statuses (range of means, 0.5 to 0.7 tests per week). Third, it is important to enactment that the consistency betwixt the comparative levels of effectiveness successful the stratified analyses successful these 2 populations provides immoderate assurance that bias related to saltation successful investigating practices whitethorn not beryllium of large concern.

Several further limitations warrant mention. Our estimates of effectiveness focused connected confirmed infections and not connected different important outcomes specified arsenic symptomatic infections oregon terrible disease. The incidence of hospitalization and decease successful our illustration was excessively debased to enactment rigorous investigation of those outcomes according to the combinations of vaccine and erstwhile corruption histories analyzed, and grounds reporting was unreliable during the survey period.³⁴ In the secondary analysis, we were besides incapable to estimation the effectiveness of a 3rd dose among persons who had had corruption during the play of delta predominance. Finally, the generalizability of our results to jails, different prisons, different high-risk populations (e.g., residents of nursing homes and wellness attraction workers), and lower-risk populations is unknown.

The findings from this survey suggest that, though mRNA vaccines and erstwhile corruption supply little extortion against corruption with the omicron variant than they did against earlier variants, boosters proceed to supply important further effectiveness, including among antecedently infected persons. Continued accent connected vaccination and different ongoing mitigation practices is indispensable successful preventing transmission, particularly successful highly susceptible populations that person already borne a disproportionately ample load of illness and disruption during the Covid-19 pandemic.

Supported successful portion by the Covid-19 Emergency Response Fund astatine Stanford University, which was established with a acquisition from the Horowitz Family Foundation; the Stanford Impact Labs Design Fellowship; and by grants from the National Institute connected Drug Abuse astatine the National Institutes of Health (R37-DA15612), the Centers for Disease Control and Prevention done the Council of State and Territorial Epidemiologists (NU38OT000297-02), and the National Science Foundation Graduate Research Fellowship Program (DGE-1656518).

Disclosure forms provided by the authors are disposable with the afloat substance of this nonfiction astatine NEJM.org.

This nonfiction was published connected October 26, 2022, astatine NEJM.org.

We convey Joseph Bick, John Dunlap, Heidi Bauer, and the different unit members astatine the California Department of Corrections and Rehabilitation for providing information and assistance with mentation of the survey results, and members of the Stanford–Center for Research and Teaching successful Economics (CIDE) Coronavirus Simulation Model modeling consortium and the Stanford Health Justice Coalition for their support.

From the Departments of Biomedical Data Science (E.T.C.) and Health Policy (L.L., D.M.S., J.D.G.-F., J.A.S.) and the Division of Infectious Diseases and Geographic Medicine (J.R.A.), Stanford University School of Medicine, and Stanford Law School (D.M.S.), Stanford, the California Department of Corrections and Rehabilitation, Sacramento (D.L.), and California Correctional Health Care Services, Elk Grove (K.L.) — each successful California.

Dr. Chin tin beryllium contacted astatine [email protected] oregon astatine the Department of Biomedical Data Science, Stanford University School of Medicine, 1265 Welch Rd., Stanford, CA 94305.

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10.1056/NEJMoa2207082-t1

Table 1. Population Counts and Weighted Characteristics of Residents and Staff astatine Baseline According to Previous Infection and Vaccination Status.*