Conceptual design for an ultra-sensitive bioaerosol detection system

The detection of aerosols in general and bioaerosols more specific has gained an increased importance in multiple fields. While environmental scientists are increasingly interested in the impacts of aerosols onto climatic effects, researchers in the security sector are looking for ways to remotely detect dangerous substances from safe distances. Additionally, due to the corona pandemic, the detection of bioaerosols has gained significant relevance in sectors like public health, transportation, and aviation. As a result, more accurate, i.e. sensitive and specific, measurement equipment is needed. Here we present the design concept for a new sensor system designed to measure thin bioaerosol clouds. For the detection air samples are excited with laser light to generate a signal based on laser induced fluorescence. The fluorescence is collected in an integration sphere to optimize signal. Inside the integration sphere multiple sensors are placed, each combined with a filter to exclude all signals not belonging to a certain, agent specific wavelength interval. Through the intelligent combination of spectral intervals, a specific characteristic of the studied air sample is measured. Based on the measured characteristic a classification is performed to determine the category of the sample. Development aims at testing indoor air quality in real time.

Empowering Health Workers to Build Public Trust in Vaccination: Experience from the International Pediatric Association's Online Vaccine Trust Course, 2020-2021.

BACKGROUND: The quality of interactions between health workers (HWs) and caregivers is key in vaccine acceptance. To optimize this, HWs need knowledge about best vaccine communication practices in person and on social media. Most pre-service curricula do not include such approaches. COVID-19 necessitated the International Pediatric Association (IPA) to shift from in-person train the trainer workshops to developing an online Vaccine Trust Course to address these gaps. METHOD: The seven-module, 8-hour Vaccine Trust Course was offered online in seven languages and promoted globally. Course outcomes for participants between September 1, 2020 and September 30, 2021 were assessed using enrollment, participation, and completion data; pre-and post-training surveys of attitudes, knowledge, and practice skills; and follow-up practice surveys 3 months post course completion. RESULTS: Of the 4,926 participants across 137 countries who registered; 2,381 (48.3 %) started the course, with 1,217 (51.1 %) completing. The majority were 25 - 39 years (57 %), female (57 %), and in pediatrics (70 %); 31 % came from India. 62 % of completers rated course structure/design as excellent, 36 % as good. Over 80 % rated the content as the most valuable aspect. Three months post training, 61 % HWs reported increased empathy towards caregivers, confidence while counseling and increased vaccine acceptance amongst their patients. 21 % identified the course as the only factor in these positive changes. CONCLUSION: Shifting from face-to-face to online training due to the COVID-19 pandemic helped increase the global reach of HWs course engagement and uptake. Trained HWs reported increased empathy towards caregivers and confidence while counseling and increased patient vaccine acceptance.

Conceptual design for an ultra-sensitive bioaerosol detection system

The detection of aerosols in general and bioaerosols more specific has gained an increased importance in multiple fields. While environmental scientists are increasingly interested in the impacts of aerosols onto climatic effects, researchers in the security sector are looking for ways to remotely detect dangerous substances from safe distances. Additionally, due to the corona pandemic, the detection of bioaerosols has gained significant relevance in sectors like public health, transportation, and aviation. As a result, more accurate, i.e. sensitive and specific, measurement equipment is needed. Here we present the design concept for a new sensor system designed to measure thin bioaerosol clouds. For the detection air samples are excited with laser light to generate a signal based on laser induced fluorescence. The fluorescence is collected in an integration sphere to optimize signal. Inside the integration sphere multiple sensors are placed, each combined with a filter to exclude all signals not belonging to a certain, agent specific wavelength interval. Through the intelligent combination of spectral intervals, a specific characteristic of the studied air sample is measured. Based on the measured characteristic a classification is performed to determine the category of the sample. Development aims at testing indoor air quality in real time. © 2022 SPIE.

Rates of Asymptomatic COVID-19 Infection and Associated Factors in Olmsted County, Minnesota, in the Prevaccination Era.

Objective: To estimate rates and identify factors associated with asymptomatic COVID-19 in the population of Olmsted County during the prevaccination era. Patients and Methods: We screened first responders (n=191) and Olmsted County employees (n=564) for antibodies to SARS-CoV-2 from November 1, 2020 to February 28, 2021 to estimate seroprevalence and asymptomatic infection. Second, we retrieved all polymerase chain reaction (PCR)-confirmed COVID-19 diagnoses in Olmsted County from March 2020 through January 2021, abstracted symptom information, estimated rates of asymptomatic infection and examined related factors. Results: Twenty (10.5%; 95% CI, 6.9%-15.6%) first responders and 38 (6.7%; 95% CI, 5.0%-9.1%) county employees had positive antibodies; an additional 5 (2.6%) and 10 (1.8%) had prior positive PCR tests per self-report or medical record, but no antibodies detected. Of persons with symptom information, 4 of 20 (20%; 95% CI, 3.0%-37.0%) first responders and 10 of 39 (26%; 95% CI, 12.6%-40.0%) county employees were asymptomatic. Of 6020 positive PCR tests in Olmsted County with symptom information between March 1, 2020, and January 31, 2021, 6% (n=385; 95% CI, 5.8%-7.1%) were asymptomatic. Factors associated with asymptomatic disease included age (0-18 years [odds ratio {OR}, 2.3; 95% CI, 1.7-3.1] and >65 years [OR, 1.40; 95% CI, 1.0-2.0] compared with ages 19-44 years), body mass index (overweight [OR, 0.58; 95% CI, 0.44-0.77] or obese [OR, 0.48; 95% CI, 0.57-0.62] compared with normal or underweight) and tests after November 20, 2020 ([OR, 1.35; 95% CI, 1.13-1.71] compared with prior dates). Conclusion: Asymptomatic rates in Olmsted County before COVID-19 vaccine rollout ranged from 6% to 25%, and younger age, normal weight, and later tests dates were associated with asymptomatic infection.

Rates of Asymptomatic COVID-19 Infection and Associated Factors in Olmsted County, MN in the Pre-Vaccination Era

Objective To estimate rates and identify factors associated with asymptomatic COVID-19 in the population of Olmsted County during the pre-vaccination era. Patients and Methods We screened first responders (N=191) and Olmsted County employees (N=564) for antibodies to SARS-CoV-2 from November 2020 to February 2021 to estimate seroprevalence and asymptomatic infection. Second, we retrieved all PCR confirmed COVID-19 diagnoses in Olmsted County from March 2020 through January 2021, ed symptom information, estimated rates of asymptomatic infection and examined related factors. Results Twenty (10.5%;95%CI: 6.9%-15.6%) first responders and thirty-eight (6.7%;95% CI: 5.0%-9.1%) county employees had positive antibodies;an additional 5 (2.6%) and 10 (1.8%) had prior positive PCR tests per self-report or medical record, but no antibodies detected. Of persons with symptom information, 4/20, (20%, 95% CI: 3.0%-37.0%) of first responders and 10/39 (26%, 95% CI: 12.6%-40.0%) county employees, were asymptomatic. Of 6,020 positive PCR tests in Olmsted County with symptom information between March 1, 2020, and January 31, 2021, 6% (n=385;95% CI: 5.8%-7.1%) were asymptomatic. Factors associated with asymptomatic disease included age [0-18 years (OR=2.3, 95% CI: 1.7-3.1) and 65+ years (OR=1.40, 95% CI: 1.0-2.0) compared to ages 19-44 years], body-mass-index [overweight OR=0.58, 95% CI: 0.44-0.77) or obese (OR=0.48, 95% CI: 0.57-0.62) compared to normal or underweight] and tests after November 20, 2020 [(OR=1.35;95% CI: 1.13-1.71) compared to prior dates]. Conclusion Asymptomatic rates in Olmsted County prior to vaccine rollout ranged from 6-25%, and younger age, normal weight, and later tests dates were associated with asymptomatic infection.

Impact of vaccine pause due to Thrombosis with thrombocytopenia syndrome (TTS) following vaccination with the Ad26.COV2.S vaccine manufactured by Janssen/Johnson & Johnson on vaccine hesitancy and acceptance among the unvaccinated population.

BACKGROUND: In response to reports of thrombosis with thrombocytopenia syndrome (TTS) post-vaccination, the Johnson & Johnson (J&J) vaccine was paused and then restarted in April 2021. Our objective was to assess whether this pause adversely impacted vaccine confidence. METHODS: Two large internet-based surveys were conducted in the US among adults to measure knowledge, attitudes and perceptions of the J&J vaccine pause and rates of vaccine hesitancy among unvaccinated persons before, during and after the pause. RESULTS: Among 66% of respondents aware of the pause, 44% identified blood clots as the reason for the pause without prompting. The impact of the pause on vaccine behavior among unvaccinated persons and perception of the vaccine safety system was mixed and modified by trust in the public health authorities. Those who were less willing to get vaccinated because of the pause were less inclined for all vaccines, not only the J&J product. Moreover, a notable proportion (22.1%) of the small number of persons (n = 30) vaccinated with the J&J vaccine after the pause reported not receiving information about the risk of TTS. The proportion of unvaccinated persons who were hesitant was increasing before and during the pause and then leveled off after the pause. CONCLUSIONS: The J&J vaccine pause is unlikely to be a major barrier to vaccine uptake. Public attitudes about vaccines may be more resilient than appreciated, especially when safety issues are investigated with transparent communication. This paper has important implications for messaging and program administration with future vaccine-specific adverse events. Efforts may be warranted to ensure all persons being offered the J&J vaccine are made aware of the risk of TTS.

Emergency department personnel patient care-related COVID-19 risk.

OBJECTIVES: Emergency department (ED) health care personnel (HCP) are at risk of exposure to SARS-CoV-2. The objective of this study was to determine the attributable risk of SARS-CoV-2 infection from providing ED care, describe personal protective equipment use, and identify modifiable ED risk factors. We hypothesized that providing ED patient care increases the probability of acquiring SARS-CoV-2 infection. METHODS: We conducted a multicenter prospective cohort study of 1,673 ED physicians, advanced practice providers (APPs), nurses, and nonclinical staff at 20 U.S. centers over 20 weeks (May to December 2020; before vaccine availability) to detect a four-percentage point increased SARS-CoV-2 incidence among HCP related to direct patient care. Participants provided monthly nasal and serology specimens and weekly exposure and procedure information. We used multivariable regression and recursive partitioning to identify risk factors. RESULTS: Over 29,825 person-weeks, 75 participants (4.5%) acquired SARS-CoV-2 infection (31 were asymptomatic). Physicians/APPs (aOR 1.07; 95% CI 0.56-2.03) did not have higher risk of becoming infected compared to nonclinical staff, but nurses had a marginally increased risk (aOR 1.91; 95% CI 0.99-3.68). Over 99% of participants used CDC-recommended personal protective equipment (PPE), but PPE lapses occurred in 22.1% of person-weeks and 32.1% of SARS-CoV-2-infected patient intubations. The following factors were associated with infection: household SARS-CoV-2 exposure; hospital and community SARS-CoV-2 burden; community exposure; and mask non-use in public. SARS-CoV-2 intubation was not associated with infection (attributable risk fraction 13.8%; 95% CI -2.0-38.2%), and nor were PPE lapses. CONCLUSIONS: Among unvaccinated U.S. ED HCP during the height of the pandemic, the risk of SARS-CoV-2 infection was similar in nonclinical staff and HCP engaged in direct patient care. Many identified risk factors were related to community exposures.

Use of Random Domain Intercept Technology to Track COVID-19 Vaccination Rates in Real Time Across the United States: Survey Study.

BACKGROUND: Accurate and timely COVID-19 vaccination coverage data are vital for informing targeted, effective messaging and outreach and identifying barriers to equitable health service access. However, gathering vaccination rate data is challenging, and efforts often result in information that is either limited in scope (eg, limited to administrative data) or delayed (impeding the ability to rapidly respond). The evaluation of innovative technologies and approaches that can assist in addressing these limitations globally are needed. OBJECTIVE: The objective of this survey study was to assess the validity of Random Domain Intercept Technology (RDIT; RIWI Corp) for tracking self-reported vaccination rates in real time at the US national and state levels. RDIT-a form of online intercept sampling-has the potential to address the limitations of current vaccination tracking systems by allowing for the measurement of additional data (eg, attitudinal data) and real-time, rapid data collection anywhere there is web access. METHODS: We used RDIT from June 30 to July 26, 2021, to reach a broad sample of US adult (aged ≥18 years) web users and asked questions related to COVID-19 vaccination. Self-reported vaccination status was used as the focus of this validation exercise. National- and state-level RDIT-based vaccination rates were compared to Centers for Disease Control and Prevention (CDC)-reported national and state vaccination rates. Johns Hopkins University's and Emory University's institutional review boards designated this project as public health practice to inform message development (not human subjects research). RESULTS: By using RDIT, 63,853 adult web users reported their vaccination status (6.2% of the entire 1,026,850 American web-using population that was exposed to the survey). At the national level, the RDIT-based estimate of adult COVID-19 vaccine coverage was slightly higher (44,524/63,853, 69.7%; 95% CI 69.4%-70.1%) than the CDC-reported estimate (67.9%) on July 15, 2021 (ie, midway through data collection; t63,852=10.06; P<.001). The RDIT-based and CDC-reported state-level estimates were strongly and positively correlated (r=0.90; P<.001). RDIT-based estimates were within 5 percentage points of the CDC's estimates for 29 states. CONCLUSIONS: This broad-reaching, real-time data stream may provide unique advantages for tracking the use of a range of vaccines and for the timely evaluation of vaccination interventions. Moreover, RDIT could be harnessed to rapidly assess demographic, attitudinal, and behavioral constructs that are not available in administrative data, which could allow for deeper insights into the real-time predictors of vaccine uptake-enabling targeted and timely interventions.

Masks, money, and mandates: A national survey on efforts to increase COVID-19 vaccination intentions in the United States.

Various efforts to increase COVID-19 vaccination rates have been employed in the United States. We sought to rapidly investigate public reactions to these efforts to increase vaccination, including self-reported responses to widespread reduced masking behavior, monetary incentive programs to get vaccinated, and work vaccination requirements. Using a unique method for data collection (Random Domain Intercept Technology), we captured a large (N = 14,152), broad-based sample of the United States Web-using population (data collected from June 30 -July 26, 2021). About 3/4 of respondents reported being vaccinated. The likelihood of vaccination and vaccination intention differed across various demographic indicators (e.g., gender, age, income, political leaning). We observed mixed reactions to efforts aimed at increasing vaccination rates among unvaccinated respondents. While some reported that specific efforts would increase their likelihood of getting vaccinated (between 16% and 32%), others reported that efforts would decrease their likelihood of getting vaccinated (between 17% and 42%). Reactions differed by general vaccination intention, as well as other demographic indicators (e.g., race, education). Our results highlight the need to fully understand reactions to policy changes, programs, and mandates before they are communicated to the public and employed. Moreover, the results emphasize the importance of understanding how reactions differ across groups, as this information can assist in targeting intervention efforts and minimizing potentially differential negative impact.

Assessing vaccine effectiveness against severe COVID-19 disease caused by omicron variant. Report from a meeting of the World Health Organization.

Vaccine effectiveness is lower and wanes faster against infection and symptomatic disease caused by the omicron variant of SARS-CoV-2 than was observed with previous variants. Vaccine effectiveness against severe omicron disease, on average, is higher, but has shown variability, including rapid apparent waning, in some studies. Assessing vaccine effectiveness against omicron severe disease using hospital admission as a measure of severe disease has become more challenging because of omicron's attenuated intrinsic severity and its high prevalence of infection. Many hospital admissions likely occur among people with incidental omicron infection or among those with infection-induced exacerbation of chronic medical conditions. To address this challenge, the World Health Organization held a virtual meeting on March 15, 2022, to review evidence from several studies that assessed Covid-19 vaccine effectiveness against severe omicron disease using several outcome definitions. Data was shown from studies in South Africa, the United States, the United Kingdom and Qatar. Several approaches were proposed that better characterize vaccine protection against severe Covid-19 disease caused by the omicron variant than using hospitalization of omicron-infected persons to define severe disease. Using more specific definitions for severe respiratory Covid-19 disease, such as indicators of respiratory distress (e.g. oxygen requirement, mechanical ventilation, and ICU admission), showed higher vaccine effectiveness than against hospital admission. Second, vaccine effectiveness against progression from omicron infection to hospitalization, or severe disease, also showed higher vaccine protection. These approaches might better characterize vaccine performance against severe Covid-19 disease caused by omicron, as well as future variants that evade humoral immunity, than using hospitalization with omicron infection as an indicator of severe disease.

Ecological super-spreaders drive host-range oscillations: Omicron and risk space for emerging infectious disease.

The unusual genetic diversity of the Omicron strain has led to speculation about its origin. The mathematical modelling platform developed for the Stockholm Paradigm (SP) indicates strongly that it has retro-colonized humans from an unidentified nonhuman mammal, likely originally infected by humans. The relationship between Omicron and all other SARS-CoV-2 variants indicates oscillations among hosts, a core part of the SP. Such oscillations result from the emergence of novel variants following colonization of new hosts, replenishing and expanding the risk space for disease emergence. The SP predicts that pathogens colonize new hosts using pre-existing capacities. Those events are thus predictable to a certain extent. Novel variants emerge after a colonization and are not predictable. This makes it imperative to take proactive measures for anticipating emerging infectious diseases (EID) and mitigating their impact. The SP suggests a policy protocol, DAMA, to accomplish this goal. DAMA comprises: DOCUMENT to detect pathogens before they emerge in new places or colonize new hosts; ASSESS to determine risk; MONITOR to detect changes in pathogen populations that increase the risk of outbreaks and ACT to prevent outbreaks when possible and minimize their impact when they occur.

Disaster Response in Italian Nursing Homes: A Qualitative Study during the COVID-19 Pandemic.

Nursing homes (NHs) have been among the care settings most affected by both the virus itself and collateral damage through infection protection and control measures (IPC). However, there is a paucity of research regarding disaster response and preparedness of these institutions. The present study aimed to analyze disaster response and management and to develop prospective strategies for disaster management in NHs. A qualitative survey including (i) residents, (ii) nursing staff, (iii) relatives of residents, and (iv) NHs' medical leads was performed. Data were collected by 45 in-depth interviews. Our results indicate that the shift from resident-centered care towards collective-protective approaches led through the suspending of established care principles to an emergency vacuum: implementable strategies were lacking and the subsequent development of temporary, immediate, and mostly suboptimal solutions by unprepared staff led to manifold organizational, medical, and ethical conflicts against the background of unclear legislation, changing protocols, and fear of legal consequences. IPC measures had long-lasting effects on the health and wellbeing of residents, relatives, and professionals. Without disaster preparedness protocols and support in decision-making during disasters, professionals in NHs are hardly able to cope with emergency situations.

Retrospective analysis of NGS data in pediatric genetic cohort: detection of rare variants that may impact influenza and COVID-19 infection

It is difficult to assign a precise frequency of infections that defines an increased susceptibility to infections reflecting an impaired immune response given the majority of patients with intact immune systems still contract multiple upper respiratory infections each year, usually of viral origin. In fact, the average child may experience up to six to eight upper respiratory infections each year. The frequency of these infections may be related to environmental exposures but also may be triggered by genetic susceptibility. As an example, respiratory disease complicates the management of several inherited metabolic diseases, either at presentation or as late-onset features. More recently, children of all ages have been shown to contract COVID-19;however, children with underlying medical conditions are at increased risk. COVID-19 has been known for almost a year now, with several studies identifying genetic risk factors are associated with severe COVID-19. In the context of a health system wide genomic medicine program “Genomic Answers for Kids” at Children’s Mercy, Kansas City, we performed a retrospective analysis of rare variants predicted to be deleterious at 12 known loci known to govern TLR3- and IRF7- dependant type I Interferon immunity of all patients/families (>2000) tested for suspected genetic disorders. We bioinformatically extracted all rare variants in those 12 genes linked to type I interferon pathway from our internal warehouse. From those, ~340 variants were further analyzed based on inheritance, minor allele frequency in population datasets, and in silico prediction. The vast majority of this subgroup of GA4 K patients were referred for a suspected neurological disorder with or without multiple congenital anomalies (~75%). Only 15% were referred for metabolic disorders. Of those, 50% have a known genetic diagnosis unrelated to Immune deficiency. Of the selected index cases, the medical records, and if available the outpatient records, were reviewed to document the occurrence of recurrent infection and/or COVID-19. Preliminary data showed 46 “extremely” rare variants were detected in 37 GA4 K patients;6/37 (16%) have ≥2 in 1–12 genes, one GA4 K patient has 4 “extremely” rare variants in IRF7, and 3/37 GA4 K patients are deceased (~1%). Moreover, a novel disease gene was uncovered in a previously undiagnosed family, of which we identified an additional two affected individuals from an international collaboration. Finally, in a family with apparently dominant transmission of tumid lupus we observe putative causal variant in gene UNC93B1 – linking chronic inflammatory disorder (with known type I interferon association) to mutations predisposing to COVID-19. Recurrent or persistent infection is usually a manifestation of primary immunodeficiency. While most children with recurrent infections have a normal immunity, it is important to remember a subset of patients have an unrecognized genetic susceptibility to infection. Further analysis and monitoring are on-going. As we are continuing to struggle with the COVID-19 pandemic, combined with flu season, understanding precisely who may be at higher risk of infection and complications is critical and could play an important role in ongoing efforts to in disease prevention and the development of better treatment protocols

Adverse events of active and placebo groups in SARS-CoV-2 vaccine randomized trials: A systematic review.

BACKGROUND: For safety assessment in clinical trials, adverse events (AEs) are reported for the drug under evaluation and compared with AEs in the placebo group. Little is known about the nature of the AEs associated with clinical trials of SARS-CoV-2 vaccines and the extent to which these can be traced to nocebo effects, where negative treatment-related expectations favor their occurrence. METHODS: In our systematic review, we compared the rates of solicited AEs in the active and placebo groups of SARS-CoV-2 vaccines approved by the Western pharmaceutical regulatory agencies.We implemented a search strategy to identify trial-III studies of SARS-CoV-2 vaccines through the PubMed database. We adopted the PRISMA Statement to perform the study selection and the data collection and identified three trial: two mRNA-based (38403 participants) and one adenovirus type (6736 participants). FINDINGS: Relative risks showed that the occurrence of AEs reported in the vaccine groups was higher compared with the placebo groups. The most frequently AEs in both groups were fatigue, headache, local pain, as injection site reactions, and myalgia. In particular, for first doses in placebo recipients, fatigue was reported in 29% and 27% in BNT162b2 and mRNA-1273 groups, respectively, and in 21% of Ad26.COV2.S participants. Headache was reported in 27% in both mRNA groups and in 24% of Ad26.COV2.S recipients. Myalgia was reported in 10% and 14% in mRNA groups (BNT162b2 and mRNA-1273, respectively) and in 13% of Ad26.COV2.S participants. Local pain was reported in 12% and 17% in mRNA groups (BNT162b2 and mRNA-1273, respectively), and in 17% of Ad26.COV2.S recipients. These AEs are more common in the younger population and in the first dose of placebo recipients of the mRNA vaccines. INTERPRETATION: Our results are in agreement with the expectancy theory of nocebo effects and suggest that the AEs associated with COVID-19 vaccines may be related to the nocebo effect. FUNDING: Fondazione CRT - Cassa di Risparmio di Torino, IT (grant number 66346, "GAIA-MENTE" 2019).

Effectiveness of mRNA Covid-19 Vaccine among U.S. Health Care Personnel.

BACKGROUND: The prioritization of U.S. health care personnel for early receipt of messenger RNA (mRNA) vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (Covid-19), allowed for the evaluation of the effectiveness of these new vaccines in a real-world setting. METHODS: We conducted a test-negative case-control study involving health care personnel across 25 U.S. states. Cases were defined on the basis of a positive polymerase-chain-reaction (PCR) or antigen-based test for SARS-CoV-2 and at least one Covid-19-like symptom. Controls were defined on the basis of a negative PCR test for SARS-CoV-2, regardless of symptoms, and were matched to cases according to the week of the test date and site. Using conditional logistic regression with adjustment for age, race and ethnic group, underlying conditions, and exposures to persons with Covid-19, we estimated vaccine effectiveness for partial vaccination (assessed 14 days after receipt of the first dose through 6 days after receipt of the second dose) and complete vaccination (assessed ≥7 days after receipt of the second dose). RESULTS: The study included 1482 case participants and 3449 control participants. Vaccine effectiveness for partial vaccination was 77.6% (95% confidence interval [CI], 70.9 to 82.7) with the BNT162b2 vaccine (Pfizer-BioNTech) and 88.9% (95% CI, 78.7 to 94.2) with the mRNA-1273 vaccine (Moderna); for complete vaccination, vaccine effectiveness was 88.8% (95% CI, 84.6 to 91.8) and 96.3% (95% CI, 91.3 to 98.4), respectively. Vaccine effectiveness was similar in subgroups defined according to age (<50 years or ≥50 years), race and ethnic group, presence of underlying conditions, and level of patient contact. Estimates of vaccine effectiveness were lower during weeks 9 through 14 than during weeks 3 through 8 after receipt of the second dose, but confidence intervals overlapped widely. CONCLUSIONS: The BNT162b2 and mRNA-1273 vaccines were highly effective under real-world conditions in preventing symptomatic Covid-19 in health care personnel, including those at risk for severe Covid-19 and those in racial and ethnic groups that have been disproportionately affected by the pandemic. (Funded by the Centers for Disease Control and Prevention.).