Prescription Opioid Dose Reductions and Potential Adverse Events: a Multi-site Observational Cohort Study in Diverse US Health Systems.

BACKGROUND: In response to the opioid crisis in the United States, population-level prescribing of opioids has been decreasing; there are concerns, however, that dose reductions are related to potential adverse events. OBJECTIVE: Examine associations between opioid dose reductions and risk of 1-month potential adverse events (emergency department (ED) visits, opioid overdose, benzodiazepine prescription fill, all-cause mortality). DESIGN: This observational cohort study used electronic health record and claims data from eight United States health systems in a prescription opioid registry (Clinical Trials Network-0084). All opioid fills (excluding buprenorphine) between 1/1/2012 and 12/31/2018 were used to identify baseline periods with mean morphine milligram equivalents daily dose of  ≥ 50 during six consecutive months. PATIENTS: We identified 60,040 non-cancer patients with  ≥ one 2-month dose reduction period (600,234 unique dose reduction periods). MAIN MEASURES: Analyses examined associations between dose reduction levels (1- < 15%, 15- < 30%, 30- < 100%, 100% over 2 months) and potential adverse events in the month following a dose reduction using logistic regression analysis, adjusting for patient characteristics. KEY RESULTS: Overall, dose reduction periods involved mean reductions of 18.7%. Compared to reductions of 1- < 15%, dose reductions of 30- < 100% were associated with higher odds of ED visits (OR 1.14, 95% CI 1.10, 1.17), opioid overdose (OR 1.41, 95% CI 1.09-1.81), and all-cause mortality (OR 1.39, 95% CI 1.16-1.67), but lower odds of a benzodiazepine fill (OR 0.83, 95% CI 0.81-0.85). Dose reductions of 15- < 30%, compared to 1- < 15%, were associated with higher odds of ED visits (OR 1.08, 95% CI 1.05-1.11) and lower odds of a benzodiazepine fill (OR 0.93, 95% CI 0.92-0.95), but were not associated with opioid overdose and all-cause mortality. CONCLUSIONS: Larger reductions for patients on opioid therapy may raise risk of potential adverse events in the month after reduction and should be carefully monitored.

Individual and neighborhood factors associated with being unvaccinated against COVID-19 among pregnant persons.

We investigated whether unvaccinated pregnant persons cluster geographically and determined factors associated with being unvaccinated using spatial and multivariate logistic regression analyses. Pregnant persons with deliveries from December 15, 2020, through September 30, 2022, at Kaiser Permanente Northern California were included. Of the 85,852 pregnant persons in the study, 46.6% were unvaccinated before and during pregnancy. Spatial analysis identified 5 clusters with high prevalence of unvaccinated pregnant persons. Within these clusters, the proportion of unvaccinated varied from 53% to 62% versus 39% outside the clusters. In covariate-adjusted analyses, residence in a cluster increased the odds of being unvaccinated by 1.64 (95% confidence interval (CI): 1.59,1.69). The odds of being unvaccinated increased among those aged 16-24 years (odds ratio [OR] = 2.69, CI: 2.55, 2.83), aged 25-34 years (OR = 1.59, CI: 1.54, 1.64) compared with age ≥ 35 years, black race (OR = 1.45, CI:1.37, 1.54), and subsidized insurance (OR = 1.32, CI: 1.26, 1.38). The odds of being unvaccinated also increased for pregnant persons living in neighborhoods where the proportion of adults with high school education or less was greater than 20%. Geographic clustering of unvaccinated pregnant persons suggests a need for population-specific-interventions to increase vaccine coverage.

Effectiveness of COVID-19 vaccination during pregnancy by circulating viral variant.

BACKGROUND: SARS-CoV-2 infection in pregnancy can result in a spectrum of asymptomatic to critical COVID-19 outcomes, including hospitalization, admission to the intensive care unit, or death. OBJECTIVE: This study aimed to investigate the effectiveness of messenger RNA COVID-19 vaccination during pregnancy against both hospitalization and infection, stratified by different variant circulations and by time since the last vaccine dose. STUDY DESIGN: This was a retrospective cohort study among pregnant persons who were members of Kaiser Permanente Northern California and delivered between December 15, 2020, and September 30, 2022. Pregnant persons who received any vaccine dose before the pregnancy onset date were excluded. The primary outcome was hospitalization for COVID-19, and the secondary outcome was polymerase chain reaction-confirmed SARS-CoV-2 infection. Exposure was receipt of a messenger RNA vaccine during pregnancy. Poisson regression was used to estimate the risk ratio of hospitalization by comparing vaccinated pregnant persons with unvaccinated pregnant persons adjusted for sociodemographic factors and calendar time. Cox regression was used to estimate the hazard ratio of infection by comparing vaccinated pregnant persons with unvaccinated pregnant persons. Vaccine effectiveness was estimated as 1 minus the rate ratio or the hazard ratio multiplied by 100. Vaccine effectiveness was estimated overall and by variant periods (before Delta, Delta, Omicron, and subvariants). RESULTS: Of 57,688 pregnant persons, 16,153 (28%) received at least 1 dose of a messenger RNA COVID-19 vaccine during pregnancy; moreover, 4404 pregnant persons tested positive for SARS-CoV-2 infection, and 108 pregnant persons were hospitalized during pregnancy. Overall, 2-dose vaccine effectiveness against hospitalization was 91% within <150 days of vaccination and 48% >150 days after vaccination. The 2-dose vaccine effectiveness within <150 days after vaccination was 100% during the original virus strain and Delta variant periods of the virus; vaccine effectiveness was 51% during the Omicron period. Of the hospitalization cases, 97% of pregnant persons were unvaccinated. During hospitalization, none of the vaccinated pregnant persons required ventilation or were admitted to the intensive care unit. Moreover, 2-dose vaccine effectiveness against infection was 54% within <150 days after vaccination and 26% ≥150 days after vaccination. CONCLUSION: Messenger RNA COVID-19 vaccination during pregnancy was effective against hospitalization for COVID-19 and SARS-CoV-2 infection. COVID-19 was mild among pregnant persons who were vaccinated compared with those who were unvaccinated. Thus, all pregnant persons should be strongly encouraged to receive messenger RNA COVID-19 vaccines to prevent severe disease.

Maternal SARS-CoV-2 vaccination and infant protection against SARS-CoV-2 during the first six months of life.

We examined the effectiveness of maternal vaccination against SARS-CoV-2 infection in 30,311 infants born at Kaiser Permanente Northern California from December 15, 2020, to May 31, 2022. Using Cox regression, the effectiveness of ≥2 doses of COVID-19 vaccine received during pregnancy was 84% (95% confidence interval [CI]: 66, 93), 62% (CI: 39, 77) and 56% (CI: 34,71) during months 0-2, 0-4 and 0- 6 of a child's life, respectively, in the Delta variant period. In the Omicron variant period, the effectiveness of maternal vaccination in these three age intervals was 21% (CI: -21,48), 14% (CI: -9,32) and 13% (CI: -3,26), respectively. Over the entire study period, the incidence of hospitalization for COVID-19 was lower during the first 6 months of life among infants of vaccinated mothers compared with infants of unvaccinated mothers (21/100,000 person-years vs. 100/100,000 person-years). Maternal vaccination was protective, but protection was lower during Omicron than during Delta. Protection during both periods decreased as infants aged.

Association of the COVID-19 Pandemic With Unstable and/or Unsafe Living Situations and Intimate Partner Violence Among Pregnant Individuals.

Importance: The social, behavioral, and economic consequences of the COVID-19 pandemic may be associated with unstable and/or unsafe living situations and intimate partner violence (IPV) among pregnant individuals. Objective: To investigate trends in unstable and/or unsafe living situations and IPV among pregnant individuals prior to and during the COVID-19 pandemic. Design, Setting, and Participants: A cross-sectional population-based interrupted time-series analysis was conducted among Kaiser Permanente Northern California members who were pregnant and screened for unstable and/or unsafe living situation and IPV as part of standard prenatal care between January 1, 2019, and December 31, 2020. Exposures: COVID-19 pandemic (prepandemic period: January 1, 2019, to March 31, 2020; during pandemic period: April 1 to December 31, 2020). Main Outcomes and Measures: The 2 outcomes were unstable and/or unsafe living situations and IPV. Data were extracted from electronic health records. Interrupted time-series models were fit and adjusted for age and race and ethnicity. Results: The study sample included 77 310 pregnancies (74 663 individuals); 27.4% of the individuals were Asian or Pacific Islander, 6.5% were Black, 29.0% were Hispanic, 32.3% were non-Hispanic White, and 4.8% were other/unknown/multiracial, with a mean (SD) age of 30.9 (5.3) years. Across the 24-month study period there was an increasing trend in the standardized rate of unsafe and/or unstable living situations (2.2%; rate ratio [RR], 1.022; 95% CI, 1.016-1.029 per month) and IPV (4.9%; RR, 1.049; 95% CI, 1.021-1.078 per month). The ITS model indicated a 38% increase (RR, 1.38; 95% CI, 1.13-1.69) in the first month of the pandemic for unsafe and/or unstable living situation, with a return to the overall trend afterward for the study period. For IPV, the interrupted time-series model suggested an increase of 101% (RR, 2.01; 95% CI, 1.20-3.37) in the first 2 months of the pandemic. Conclusions and Relevance: This cross-sectional study noted an overall increase in unstable and/or unsafe living situations and IPV over the 24-month period, with a temporary increase associated with the COVID-19 pandemic. It may be useful for emergency response plans to include IPV safeguards for future pandemics. These findings suggest the need for prenatal screening for unsafe and/or unstable living situations and IPV coupled with referral to appropriate support services and preventive interventions.

The association between buprenorphine treatment duration and mortality: a multi-site cohort study of people who discontinued treatment.

BACKGROUND AND AIMS: Buprenorphine is an effective medication for opioid use disorder that reduces mortality; however, many patients are not retained in buprenorphine treatment, and an optimal length of treatment after which patients can safely discontinue treatment has not been identified. This study measured the association between buprenorphine treatment duration and all-cause mortality among patients who discontinued treatment. Secondary objectives were to measure the association between treatment duration and drug overdose and opioid-related overdoses. DESIGN: Multi-site cohort study. SETTING: Eight US health systems. PARTICIPANTS: Patients who initiated and discontinued buprenorphine treatment between 1 January 2012 and 31 December 2018 (n = 6550). Outcomes occurring after patients discontinued buprenorphine treatment were compared between patients who initiated and discontinued treatment after 8-30, 31-90, 91-180, 181-365 and > 365 days. MEASUREMENTS: Covariate data were obtained from electronic health records (EHRs). Mortality outcomes were derived from EHRs and state vital statistics. Non-fatal opioid and drug overdoses were obtained from diagnostic codes. Four sites provided cause-of-death data to identify fatal drug and opioid-related overdoses. Adjusted frailty regression was conducted on a propensity-weighted cohort to assess associations between duration of the final treatment episode and outcomes. FINDINGS: The mortality rate after buprenorphine treatment was 1.82 per 100 person-years (n = 191 deaths). In regression analyses with > 365 days as the reference group, treatment duration was not associated with all-cause mortality and drug overdose (P > 0.05 for both). However, compared with > 365 days of treatment, 91-180 days of treatment was associated with increased opioid overdose risk (hazard ratio = 2.94, 95% confidence interval = 1.11-7.79). CONCLUSIONS: Among patients who discontinue buprenorphine treatment, there appears to be no treatment duration period associated with a reduced risk for all-cause mortality. Patients who discontinue buprenorphine treatment after 91-180 days appear to be at heightened risk for opioid overdose compared with patients who discontinue after > 365 days of treatment.

Association of cannabis use during pregnancy with severe acute respiratory syndrome coronavirus 2 infection: a retrospective cohort study.

BACKGROUND AND AIMS: Cannabis use is increasingly common among pregnant individuals and might be a risk factor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We aimed to test whether prenatal cannabis use is associated with increased risk of SARS-CoV-2 infection during pregnancy. DESIGN: This is a retrospective cohort study. SETTING: The study was conducted in California, USA. PARTICIPANTS: A total of 58 114 pregnancies (with outcomes from 5 March 2020 to 30 September 2021) among 57 287 unique pregnant women aged 14-54 years who were screened for prenatal substance use, enrolled in Kaiser Permanente Northern California (KPNC) (a health-care system) and had not tested positive for COVID-19 prior to pregnancy onset. MEASUREMENTS: We utilized data from the KPNC electronic health record. Cannabis use status (current, recently quit and non-user) was based on universal screenings during prenatal care (including urine toxicology testing and self-reported use on a self-administered questionnaire). SARS-CoV-2 infection [based on polymerase chain reaction (PCR) tests] was estimated in time-to-event analyses using Cox proportional hazard regression models adjusting for covariates. Secondary analyses examined differences in (a) SARS-CoV-2 testing rates and (b) SARS-CoV-2 infection rates among those tested. FINDINGS: We observed 348 810 person-months of follow-up time in our cohort with 41 064 SARS-CoV-2 PCR tests and 6% (n = 2414) of tests being positive. At the start of follow-up, 7% of pregnant individuals had current use, 12% had recently quit and 81% did not use cannabis. Adjusting for covariates, current use was associated with lower rates of SARS-CoV-2 infection [adjusted hazard ratio (aHR) = 0.60, 95% confidence interval (CI) = 0.49-0.74 than non-use. Those who had recently quit did not differ from non-cannabis users in infection rates (aHR = 0.96, 95% CI = 0.86-1.08). Sensitivity analyses among patients who received a SARS-CoV-2 test also found lower odds of infection associated with current versus no cannabis use (aOR = 0.76, CI = 0.61-0.93). CONCLUSIONS: Current cannabis use appears to be associated with a reduced risk of SARS-CoV-2 infection among pregnant individuals.

Maternal SARS-CoV-2 Vaccination and Infant Protection Against SARS-CoV-2 During the First 6 Months of Life.

We examined the effectiveness of maternal vaccination against SARS-CoV-2 infection in 30,288 infants born at Kaiser Permanente Northern California from December 15, 2020, to May 31, 2022. Using Cox regression, the effectiveness of maternal vaccination was 85% (95% confidence interval [CI]: 67, 93), 64% (CI: 43, 78) and 57% (CI: 36,71) during the first 2, 4 and 6 months of life, respectively, in the Delta variant period. In the Omicron variant period, the effectiveness of maternal vaccination in these three age intervals was 22% (CI: -18,48), 14% (CI: -10,32) and 12% (CI: -4,26), respectively. Over the entire study period, the incidence of hospitalization for COVID-19 was lower during the first 6 months of life among infants of vaccinated mothers compared with infants of unvaccinated mothers (21/100,000 person-years vs. 100/100,000 person-years). Maternal vaccination was protective, but protection was lower during Omicron than during Delta. Protection during both periods decreased as infants aged.

Prescribing for different antibiotic classes across age groups in the Kaiser Permanente Northern California population in association with influenza incidence, 2010-2018.

There is limited information on the volume of antibiotic prescribing that is influenza-associated, resulting from influenza infections and their complications (such as streptococcal pharyngitis). We estimated that for the Kaiser Permanente Northern California population during 2010-2018, 3.4% (2.8%-4%) of all macrolide prescriptions (fills), 2.7% (2.3%-3.2%) of all aminopenicillin prescriptions, 3.1% (2.4%-3.9%) of all 3rd generation cephalosporins prescriptions, 2.2% (1.8%-2.6%) of all protected aminopenicillin prescriptions and 1.3% (1%-1.6%) of all quinolone prescriptions were influenza-associated. The corresponding proportions were higher for select age groups, e.g. 4.3% of macrolide prescribing in ages over 50 years, 5.1% (3.3%-6.8%) of aminopenicillin prescribing in ages 5-17 years and 3.3% (1.9%-4.6%) in ages <5 years was influenza-associated. The relative contribution of influenza to antibiotic prescribing for respiratory diagnoses without a bacterial indication in ages over 5 years was higher than the corresponding relative contribution to prescribing for all diagnoses. Our results suggest a modest benefit of increasing influenza vaccination coverage for reducing prescribing for the five studied antibiotic classes, particularly for macrolides in ages over 50 years and aminopenicillins in ages <18 years, and the potential benefit of other measures to reduce unnecessary antibiotic prescribing for respiratory diagnoses with no bacterial indication, both of which may contribute to the mitigation of antimicrobial resistance.

Development and implementation of a prescription opioid registry across diverse health systems.

Objective: Develop and implement a prescription opioid registry in 10 diverse health systems across the US and describe trends in prescribed opioids between 2012 and 2018. Materials and Methods: Using electronic health record and claims data, we identified patients who had an outpatient fill for any prescription opioid, and/or an opioid use disorder diagnosis, between January 1, 2012 and December 31, 2018. The registry contains distributed files of prescription opioids, benzodiazepines and other select medications, opioid antagonists, clinical diagnoses, procedures, health services utilization, and health plan membership. Rates of outpatient opioid fills over the study period, standardized to health system demographic distributions, are described by age, gender, and race/ethnicity among members without cancer. Results: The registry includes 6 249 710 patients and over 40 million outpatient opioid fills. For the combined registry population, opioid fills declined from a high of 0.718 per member-year in 2013 to 0.478 in 2018, and morphine milligram equivalents (MMEs) per fill declined from 985 MMEs per fill in 2012 to 758 MMEs in 2018. MMEs per member declined from 692 MMEs per member in 2012 to 362 MMEs per member in 2018. Conclusion: This study established a population-based opioid registry across 10 diverse health systems that can be used to address questions related to opioid use. Initial analyses showed large reductions in overall opioid use per member among the combined health systems. The registry will be used in future studies to answer a broad range of other critical public health issues relating to prescription opioid use.

Antibiotic prescribing across age groups in the Kaiser Permanente Northern California population in association with different diagnoses, and with influenza incidence, 2010-2018.

There is limited information on the volume of antibiotic prescribing that is influenza-associated, resulting from influenza infections and their complications (such as streptococcal pharyngitis and otitis media). Here, we estimated age/diagnosis-specific proportions of antibiotic prescriptions (fills) for the Kaiser Permanente Northern California population during 2010-2018 that were influenza-associated. The proportion of influenza-associated antibiotic prescribing among all antibiotic prescribing was higher in children aged 5-17 years compared to children aged under 5 years, ranging from 1.4% [95% CI (0.7-2.1)] in aged <1 year to 2.7% (1.9-3.4) in aged 15-17 years. For adults aged over 20 years, the proportion of influenza-associated antibiotic prescribing among all antibiotic prescribing was lower, ranging from 0.7% (0.5-1) for aged 25-29 years to 1.6% (1.2-1.9) for aged 60-64 years. Most of the influenza-associated antibiotic prescribing in children aged under 10 years was for ear infections, while for age groups over 25 years, 45-84% of influenza-associated antibiotic prescribing was for respiratory diagnoses without a bacterial indication. This suggests a modest benefit of increasing influenza vaccination coverage for reducing antibiotic prescribing, as well as the potential benefit of other measures to reduce unnecessary antibiotic prescribing for respiratory diagnoses with no bacterial indication in persons aged over 25 years, both of which may further contribute to the mitigation of antimicrobial resistance.

Racial Disparities in COVID-19 Testing and Outcomes : Retrospective Cohort Study in an Integrated Health System.

BACKGROUND: Racial disparities exist in outcomes after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. OBJECTIVE: To evaluate the contribution of race/ethnicity in SARS-CoV-2 testing, infection, and outcomes. DESIGN: Retrospective cohort study (1 February 2020 to 31 May 2020). SETTING: Integrated health care delivery system in Northern California. PARTICIPANTS: Adult health plan members. MEASUREMENTS: Age, sex, neighborhood deprivation index, comorbid conditions, acute physiology indices, and race/ethnicity; SARS-CoV-2 testing and incidence of positive test results; and hospitalization, illness severity, and mortality. RESULTS: Among 3 481 716 eligible members, 42.0% were White, 6.4% African American, 19.9% Hispanic, and 18.6% Asian; 13.0% were of other or unknown race. Of eligible members, 91 212 (2.6%) were tested for SARS-CoV-2 infection and 3686 had positive results (overall incidence, 105.9 per 100 000 persons; by racial group, White, 55.1; African American, 123.1; Hispanic, 219.6; Asian, 111.7; other/unknown, 79.3). African American persons had the highest unadjusted testing and mortality rates, White persons had the lowest testing rates, and those with other or unknown race had the lowest mortality rates. Compared with White persons, adjusted testing rates among non-White persons were marginally higher, but infection rates were significantly higher; adjusted odds ratios [aORs] for African American persons, Hispanic persons, Asian persons, and persons of other/unknown race were 2.01 (95% CI, 1.75 to 2.31), 3.93 (CI, 3.59 to 4.30), 2.19 (CI, 1.98 to 2.42), and 1.57 (CI, 1.38 to 1.78), respectively. Geographic analyses showed that infections clustered in areas with higher proportions of non-White persons. Compared with White persons, adjusted hospitalization rates for African American persons, Hispanic persons, Asian persons, and persons of other/unknown race were 1.47 (CI, 1.03 to 2.09), 1.42 (CI, 1.11 to 1.82), 1.47 (CI, 1.13 to 1.92), and 1.03 (CI, 0.72 to 1.46), respectively. Adjusted analyses showed no racial differences in inpatient mortality or total mortality during the study period. For testing, comorbid conditions made the greatest relative contribution to model explanatory power (77.9%); race only accounted for 8.1%. Likelihood of infection was largely due to race (80.3%). For other outcomes, age was most important; race only contributed 4.5% for hospitalization, 12.8% for admission illness severity, 2.3% for in-hospital death, and 0.4% for any death. LIMITATION: The study involved an insured population in a highly integrated health system. CONCLUSION: Race was the most important predictor of SARS-CoV-2 infection. After infection, race was associated with increased hospitalization risk but not mortality. PRIMARY FUNDING SOURCE: The Permanente Medical Group, Inc.

Individual and Neighborhood Factors Associated With Failure to Vaccinate Against Influenza During Pregnancy.

Uptake of influenza vaccine among pregnant women remains low. We investigated whether unvaccinated pregnant women were clustered geographically and determined factors associated with failure to vaccinate using spatial and multivariate logistic regression analyses. Pregnant women who were members of Kaiser Permanente Northern California in 2015 or 2016 were included in the study. More than half (53%) of the 77,607 included pregnant women were unvaccinated. Spatial analysis identified 5 clusters with a high prevalence of unvaccinated pregnant women. The proportion of unvaccinated women ranged from 57% to 75% within clusters as compared with 51% outside clusters. In covariate-adjusted analyses, residence in a cluster was associated with a 41% increase in the odds of being unvaccinated (odds ratio (OR) = 1.41, 95% confidence interval (CI): 1.36, 1.46). The odds of being unvaccinated were greater for Black women (OR = 1.58, 95% CI: 1.49, 1.69), Hispanic women (OR = 1.15, 95% CI: 1.05, 1.25), women with subsidized health insurance (OR = 1.18, 95% CI: 1.11, 1.24), women with fewer than 5 prenatal-care visits (OR = 1.85, 95% CI: 1.60, 2.16), and neighborhoods with a high deprivation index (fourth quartile vs. first: OR = 1.14, 95% CI: 1.07, 1.21). In conclusion, unvaccinated pregnant women were clustered geographically and by key sociodemographic factors. These findings suggest that interventions to increase influenza vaccine coverage among pregnant women are needed, particularly in vulnerable populations.

The role of substance use disorders in experiencing a repeat opioid overdose, and substance use treatment patterns among patients with a non-fatal opioid overdose.

BACKGROUND: A non-fatal opioid overdose (NFOO) increases the risk of another overdose and identifies high-risk patients. We estimated the risk of repeat opioid overdose for patients with and without substance use disorder (SUD) diagnoses and the change in substance use treatment utilization rates associated with the first NFOO. METHODS: We selected patients (>18 years of age) from Kaiser Permanente Northern California with a NFOO between 2009-2016 (n = 3,992). Cox proportional hazards models estimated the 1-year risk of opioid overdose associated with SUD diagnoses (opioid, alcohol, cannabis, amphetamine, sedative, and cocaine), controlling for patient characteristics. Among patients with an index NFOO, we calculated monthly utilization rates for outpatient substance use services and buprenorphine before and after the index overdose. Interrupted time series models estimated the change in level and trend in utilization rates associated with the index overdose. RESULTS: Approximately 7.2 % of patients had a repeat opioid overdose during the year after the index NFOO. The only SUD diagnosis significantly associated with greater risk of repeat overdose was opioid use disorder (OUD) (aHR: 1.51; 95 % CI: 1.13-2.01). Before the index overdose, 4.16 % of patients received outpatient substance use services and 1.32 % received buprenorphine. The index overdose was associated with a 5.94 % (standard error: 0.77 %) absolute increase in outpatient substance use services and a 1.29 % (standard error: 0.15 %) increase in buprenorphine. CONCLUSION: Patients with a NFOO and OUD are vulnerable to another overdose. Low initiation rates for substance use treatment after a NFOO indicate a need to address patient, provider, and system barriers.

Depletion-of-susceptibles Bias in Analyses of Intra-season Waning of Influenza Vaccine Effectiveness.

Bias arises in studies of waning vaccine effectiveness when higher-risk individuals are depleted from the at-risk population at different rates between study groups. We examined how this bias arises and how to avoid it. A reanalysis of data from California confirmed a finding of intra-season waning of influenza vaccine effectiveness.

Intraseason Waning of Influenza Vaccine Effectiveness.

BACKGROUND: In the United States, it is recommended that healthcare providers offer influenza vaccination by October, if possible. However, if the vaccine's effectiveness soon begins to wane, the optimal time for vaccination may be somewhat later. We examined whether the effectiveness of influenza vaccine wanes during the influenza season with increasing time since vaccination. METHODS: We identified persons who were vaccinated with inactivated influenza vaccine from 1 September 2010 to 31 March 2017 and who were subsequently tested for influenza and respiratory syncytial virus (RSV) by a polymerase chain reaction test. Test-confirmed influenza was the primary outcome and days-since-vaccination was the predictor of interest in conditional logistic regression. Models were adjusted for age and conditioned on calendar day and geographic area. RSV was used as a negative-control outcome. RESULTS: Compared with persons vaccinated 14 to 41 days prior to being tested, persons vaccinated 42 to 69 days prior to being tested had 1.32 (95% confidence interval [CI], 1.11 to 1.55) times the odds of testing positive for any influenza. The odds ratio (OR) increased linearly by approximately 16% for each additional 28 days since vaccination. The OR was 2.06 (95% CI, 1.69 to 2.51) for persons vaccinated 154 or more days prior to being tested. No evidence of waning was found for RSV. CONCLUSIONS: Our results suggest that effectiveness of inactivated influenza vaccine wanes during the course of a single season. These results may lead to reconsideration of the optimal timing of seasonal influenza vaccination.