Protection against Omicron conferred by mRNA primary vaccine series, boosters, and prior infection

BO_SCPLOWACKGROUNDC_SCPLOWPrisons and jails are high-risk settings for Covid-19 transmission, morbidity, and mortality. We evaluate protection conferred by prior infection and vaccination against the SARS-CoV-2 Omicron variant within the California state prison system. MO_SCPLOWETHODSC_SCPLOWWe employed a test-negative design to match resident and staff cases during the Omicron wave (December 24, 2021--April 14, 2022) to controls according to a cases test-week as well as demographic, clinical, and carceral characteristics. We estimated protection against infection using conditional logistic regression, with exposure status defined by vaccination, stratified by number of mRNA doses received, and prior infection, stratified by periods before or during Delta variant predominance. RO_SCPLOWESULTSC_SCPLOWWe matched 15,783 resident and 8,539 staff cases to 180,169 resident and 90,409 staff controls. Among cases, 29.7% and 2.2% were infected before or during the emergence of the Delta variant, respectively; 30.6% and 36.3% were vaccinated with two or three doses, respectively. Estimated protection from Omicron infection for two and three doses were 14.9% (95% Confidence Interval [CI], 12.3--19.7%) and 43.2% (42.2--47.4%) for those without known prior infections, 47.8% (95% CI, 46.6--52.8%) and 61.3% (95% CI, 60.7--64.8%) for those infected before the emergence of Delta, and 73.1% (95% CI, 69.8--80.1%) and 86.8% (95% CI, 82.1--92.7) for those infected during the period of Delta predominance. CO_SCPLOWONCLUSIONC_SCPLOWA third mRNA dose provided significant, additional protection over two doses, including among individuals with prior infection. Our findings suggest that vaccination should remain a priority--even in settings with high levels of transmission and prior infection.

Waning of Vaccine-Conferred Protection against SARS-CoV-2 Infection: Matched Case-Control Test-Negative Design Study in Two High-Risk Populations

To distinguish waning of vaccine responses from differential variant protection, we performed a test-negative case-control analysis during a Delta variant-dominant period in Californias prisons. We found that infection odds increased each 28-day period post-vaccination, reaching 3.4-fold (residents) to 4.7-fold (staff) increased odds of infection after 180 days.

Uptake of Covid-19 vaccines among frontline workers in California state prisons

BackgroundPrisons are high-risk environments for Covid-19. Vaccination levels among prison staff remain troublingly low - lower than levels among residents and members of the surrounding community. The situation is troubling because prison staff are a key vector for Covid-19 transmission. ObjectiveTo assess patterns and timing of staff vaccination in California state prisons and identify individual- and community-level factors associated with being unvaccinated. DesignWe calculated fractions of prison staff and incarcerated residents in California state prisons who remained unvaccinated. Adjusted analyses identified demographic, community, and peer factors associated with vaccination uptake among staff. SettingCalifornia Department of Corrections and Rehabilitation prisons. ParticipantsCustody and healthcare staff who worked in direct contact with residents. Main Outcomes and MeasuresRemaining unvaccinated through June 30, 2021. ResultsA total of 26% of custody staff and 52% of healthcare staff took [≥]1 dose in the first two months of vaccine offer; uptake stagnated thereafter. By June 30, 2021, 61% of custody and 37% of healthcare staff remained unvaccinated. Remaining unvaccinated was positively associated with younger age, prior Covid-19, residing in a community with relatively low vaccination rates, and sharing shifts with co-workers who had relatively low vaccination rates. Conclusions and RelevanceVaccine uptake among prison staff in California in regular contact with incarcerated residents has plateaued at levels that pose ongoing risks--both of further outbreaks in the prisons and transmission into surrounding communities. Staff decisions to forego vaccination appear to be complex and multifactorial. Achieving safe levels of vaccine protection among frontline staff may necessitate requiring vaccination as condition of employment.

Outbreaks of Covid-19 Variants in Prisons: A Mathematical Modeling Analysis of Vaccination and Re-Opening Policies

BackgroundResidents of correctional facilities have experienced disproportionately higher rates of SARS-CoV-2 infection and Covid-19-related mortality. To protect against outbreaks, many prisons and jails imposed heavy restrictions on in-person activities, which are now beginning to lift. Uncertainty surrounds the safety of these moves. Methods and FindingsWe obtained system-wide resident-day level data for the California state prison system, the nations third largest. We used the data to develop a transmission-dynamic stochastic microsimulation model that projects the impact of various policy scenarios on risks of SARS-CoV-2 infections and related hospitalization among residents after an initial infection is introduced to a prison. The policy scenarios vary according to levels of vaccine coverage, baseline immunity, resumption of activities, and use of non-pharmaceutical interventions (e.g., masking, physical distancing). The analyses were conducted across 5 types of prisons that differed in their residential layouts, security levels, and resident demographics. If a viral variant is introduced into a prison that has resumed pre-2020 contact levels, has moderate vaccine coverage, and has no baseline immunity, 23-74% of residents are expected to be infected over 200 days. High vaccination coverage coupled with use of non-pharmaceutical measures reduces cumulative infections to 2-54% of residents. In prisons consisting mostly of dormitory housing, even with high vaccine coverage and non-pharmaceutical interventions, resumption of in-person activities is associated with substantial risk, unless there is high baseline immunity (e.g., [≥]50%) from prior outbreaks. In prisons consisting mostly of cell housing, <10% of residents are expected to become infected, even with no baseline immunity. However, hospitalization risks are substantial in prisons that house medically vulnerable populations, even for prisons consisting mostly of cells. Risks of large outbreaks are substantially higher if there is continued introduction of infections into a prison. Some findings may not be transportable to other carceral settings, and our assumptions regarding viral variants will not be accurate for all variants. ConclusionsBalancing the benefits of resuming normal in-person activities against the risks of Covid-19 outbreaks is a difficult challenge for correctional systems. The policy choices are not strictly binary. To protect against viral variants, prisons should focus on achieving both high vaccine coverage and maintaining widespread use of non-pharmaceutical interventions. With both in place, some prisons, especially those with lower room occupancy that have already had large outbreaks, could safely resume in-person activities, while continuing testing and measures to protect the medically-vulnerable.

Covid-19 in the California State Prison System: An Observational Study of Decarceration, Ongoing Risks, and Risk Factors

BackgroundCorrectional institutions nationwide are seeking to mitigate Covid-19-related risks. ObjectiveTo quantify changes to Californias prison population since the pandemic began and identify risk factors for Covid-19 infection. DesignWe described residents demographic characteristics, health status, Covid-19 risk scores, room occupancy, and labor participation. We used Cox proportional hazard models to estimate the association between rates of Covid-19 infection and room occupancy and out-of-room labor, respectively. SettingCalifornia state prisons (March 1-October 10, 2020). ParticipantsResidents of California state prisons. MeasurementsChanges in the incarcerated populations size, composition, housing, and activities. For the risk factor analysis, the exposure variables were room type (cells vs dormitories) and labor participation (any room occupant participating in the prior 2 weeks) and the outcome variable was incident Covid-19 case rates. ResultsThe incarcerated population decreased 19.1% (119,401 to 96,623) during the study period.On October 10, 2020, 11.5% of residents were aged [≥]60, 18.3% had high Covid-19 risk scores, 31.0% participated in out-of-room labor, and 14.8% lived in rooms with [≥]10 occupants. Nearly 40% of residents with high Covid-19 risk scores lived in dormitories. In 9 prisons with major outbreaks (6,928 rooms; 21,750 residents), dormitory residents had higher infection rates than cell residents (adjusted hazard ratio [AHR], 2.51 95%CI, 2.25-2.80) and residents of rooms with labor participation had higher rates than residents of other rooms (AHR, 1.56; 95%CI, 1.39-1.74). LimitationsInability to measure density of residents living conditions or contact networks among residents and staff. ConclusionDespite reductions in room occupancy and mixing, California prisons still house many medically vulnerable residents in risky settings. Reducing risks further requires a combination of strategies, including rehousing, decarceration, and vaccination. Funding SourcesHorowitz Family Foundation; National Institute on Drug Abuse; National Science Foundation Graduate Research Fellowship; Open Society Foundations.

Longitudinal SARS-CoV-2 serosurveillance of over ten thousand health care workers in the Providence Oregon cohort.

Frontline healthcare workers (HCW) are a high-risk population for SARS-CoV-2 infection. Here we present results from a large serosurveillance study of 10,019 asymptomatic HCW conducted during April-May 2020, in eight hospital medical centers across the state of Oregon, USA during the initial peak of the pandemic. Free and voluntary testing was performed at 14 +/- 3 day intervals, over a 4-week window at each site, utilizing a lab-developed ELISA based on the Epitope Diagnostics COVID-19 nucleocapsid IgG detection Kit. We identified 253 SARS-CoV-2 IgG seropositive individuals among 10,019 total participants, representing a cross-sectional seroprevalence of 2.53%. Subgroup analysis identified differential seropositivity by job role, ranging from 8.03% among housekeepers, odds ratio 3.17 (95% CI 1.59-5.71), to 0.00% among anesthesiologists, odds ratio 0.00 (95% CI 0-0.26), both of which were significant. Over the course of the study, 17 seroconversions (0.25%) and 101 seroreversions (1.50%) were identified. Self-reported SARS-CoV-2 swab qPCR testing, when compared with subsequent serology on study, showed only modest agreement,{kappa} = 0.47 (95% CI 0.32-0.62). Overall, these findings demonstrate relatively low seroprevalence and very low seroconversion rates among HCW in Oregon, USA, over a period in which aggressive social distancing measures were in place. The high rate of seroreversion observed in this cohort, and the relatively high discordance between SARS-CoV-2 serology and swab qPCR, highlight limitations of current detection methods, and stress the need for development of novel assessment methodologies to more accurately identify exposure (and/or immunity) to SARS-CoV-2 in this population.