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A study with a test-negative design analyzed 41,552 admissions to 187 hospitals and 21,522 visits to 221 EDs or urgent care clinics. The mRNA-based vaccines (≥14 days after the second dose) were highly effective against SARS-CoV-2 infection leading to hospitalization (89%), ICU admission (90%), or an urgent care visit (91%).

Understanding the long-term impact of the COVID-19 pandemic on health care utilization is important to health care organizations and policy makers for strategic planning, as well as to researchers when designing studies that use observational electronic health record data during the pandemic period. This study aimed to evaluate the changes in health care utilization across all care settings among a large, diverse, and insured population in the United States during the COVID-19 pandemic. We conducted a retrospective cohort study within 8 health care organizations participating in the Vaccine Safety Datalink Project using electronic health record data from members of all ages from January 1, 2017, to December 31, 2021. The visit rates per person-year were calculated monthly during the study period for 4 health care settings combined as well as by inpatient, emergency department (ED), outpatient, and telehealth settings, both among all members and members without COVID-19. Difference-in-difference analysis and interrupted time series analysis were performed to assess the changes in visit rates from the prepandemic period (January 2017 to February 2020) to the early pandemic period (April-December 2020) and the later pandemic period (July-December 2021), respectively. An exploratory analysis was also conducted to assess trends through June 2023 at one of the largest sites, Kaiser Permanente Southern California. The study included more than 11 million members from 2017 to 2021. Compared with the prepandemic period, we found reductions in visit rates during the early pandemic period for all in-person care settings. During the later pandemic period, overall use reached 8.36 visits per person-year, exceeding the prepandemic level of 7.49 visits per person-year in 2019 (adjusted percent change 5.1%, 95% CI 0.6%-9.9%); inpatient and ED visits returned to prepandemic levels among all members, although they remained low at 0.095 and 0.241 visits per person-year, indicating a 7.5% and 8% decrease compared to pre-pandemic levels among members without COVID-19, respectively. Telehealth visits, which were approximately 42% of the volume of outpatient visits during the later pandemic period, were increased by 97.5% (95% CI 86.0%-109.7%) from 0.865 visits per person-year in 2019 to 2.35 visits per person-year in the later pandemic period. The trends in Kaiser Permanente Southern California were similar to those of the entire study population. Visit rates from January 2022 to June 2023 were stable and appeared to be a continuation of the use levels observed at the end of 2021. Telehealth services became a mainstay of the health care system during the late COVID-19 pandemic period. Inpatient and ED visits returned to prepandemic levels, although they remained low among members without evidence of COVID-19. Our findings provide valuable information for strategic resource allocation for postpandemic patient care and for designing observational studies involving the pandemic period.

AbstractObjectiveTo estimate the effectiveness of mRNA vaccines against moderate and severe covid-19 in adults by time since second, third, or fourth doses, and by age and immunocompromised status.DesignTest negative case-control study.SettingHospitals, emergency departments, and urgent care clinics in 10 US states, 17 January 2021 to 12 July 2022.Participants893 461 adults (≥18 years) admitted to one of 261 hospitals or to one of 272 emergency department or 119 urgent care centers for covid-like illness tested for SARS-CoV-2.Main outcome measuresThe main outcome was waning of vaccine effectiveness with BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) vaccine during the omicron and delta periods, and the period before delta was dominant using logistic regression conditioned on calendar week and geographic area while adjusting for age, race, ethnicity, local virus circulation, immunocompromised status, and likelihood of being vaccinated.Results45 903 people admitted to hospital with covid-19 (cases) were compared with 213 103 people with covid-like illness who tested negative for SARS-CoV-2 (controls), and 103 287 people admitted to emergency department or urgent care with covid-19 (cases) were compared with 531 168 people with covid-like illness who tested negative for SARS-CoV-2. In the omicron period, vaccine effectiveness against covid-19 requiring admission to hospital was 89% (95% confidence interval 88% to 90%) within two months after dose 3 but waned to 66% (63% to 68%) by four to five months. Vaccine effectiveness of three doses against emergency department or urgent care visits was 83% (82% to 84%) initially but waned to 46% (44% to 49%) by four to five months. Waning was evident in all subgroups, including young adults and individuals who were not immunocompromised; although waning was morein people who were immunocompromised. Vaccine effectiveness increased among most groups after a fourth dose in whom this booster was recommended.ConclusionsEffectiveness of mRNA vaccines against moderate and severe covid-19 waned with time after vaccination. The findings support recommendations for a booster dose after a primary series and consideration of additional booster doses.

Respiratory syncytial virus vaccines first recommended for use during 2023 were efficacious against lower respiratory tract disease in clinical trials. Limited real-world data regarding respiratory syncytial virus vaccine effectiveness are available. To inform vaccine policy and address gaps in evidence from the clinical trials, we aimed to assess the effectiveness against respiratory syncytial virus-associated hospitalisations and emergency department encounters among adults aged at least 60 years. We conducted a test-negative design analysis in an electronic health records-based network in eight states in the USA, including hospitalisations and emergency department encounters with respiratory syncytial virus-like illness among adults aged at least 60 years who underwent respiratory syncytial virus testing from Oct 1, 2023, to March 31, 2024. Respiratory syncytial virus vaccination status at the time of the encounter was derived from electronic health record documentation, state and city immunisation registries, and, for some sites, medical claims. Vaccine effectiveness was estimated by immunocompromise status, comparing the odds of vaccination among respiratory syncytial virus-positive case patients and respiratory syncytial virus-negative control patients, and adjusting for age, race and ethnicity, sex, calendar day, social vulnerability index, number of underlying non-respiratory medical conditions, presence of respiratory underlying medical conditions, and geographical region. Among 28 271 hospitalisations for respiratory syncytial virus-like illness among adults aged at least 60 years without immunocompromising conditions, vaccine effectiveness was 80% (95% CI 71–85) against respiratory syncytial virus-associated hospitalisations, and vaccine effectiveness was 81% (52–92) against respiratory syncytial virus-associated critical illness (ICU admission or death, or both). Among 8435 hospitalisations for respiratory syncytial virus-like illness among adults with immunocompromising conditions, vaccine effectiveness was 73% (48–85) against associated hospitalisation. Among 36 521 emergency department encounters for respiratory syncytial virus-like illness among adults aged at least 60 years without an immunocompromising condition, vaccine effectiveness was 77% (70–83) against respiratory syncytial virus-associated emergency department encounters. Vaccine effectiveness estimates were similar by age group and product type. Respiratory syncytial virus vaccination was effective in preventing respiratory syncytial virus-associated hospitalisations and emergency department encounters among adults aged at least 60 years in the USA during the 2023–24 respiratory syncytial virus season, which was the first season after respiratory syncytial virus vaccine was approved. The Centers for Disease Control and Prevention.

On March 13, 2020, the president of the United States declared a national emergency in response to the coronavirus disease 2019 (COVID-19) pandemic (1). With reports of laboratory-confirmed cases in all 50 states by that time (2), disruptions were anticipated in the U.S. health care system's ability to continue providing routine preventive and other nonemergency care. In addition, many states and localities issued shelter-in-place or stay-at-home orders to reduce the spread of COVID-19, limiting movement outside the home to essential activities (3). On March 24, CDC posted guidance emphasizing the importance of routine well child care and immunization, particularly for children aged ≤24 months, when many childhood vaccines are recommended.

The Vaccine Safety Datalink (VSD) uses vaccination data from electronic health records (EHR) at eight integrated health systems to monitor vaccine safety. Accurate capture of data from vaccines administered outside of the health system is critical for vaccine safety research, especially for COVID-19 vaccines, where many are administered in non-traditional settings. However, timely access and inclusion of data from Immunization Information Systems (IIS) into VSD safety assessments is not well understood. We surveyed the eight data-contributing VSD sites to assess: 1) status of sending data to IIS; 2) status of receiving data from IIS; and 3) integration of IIS data into the site EHR. Sites reported separately for COVID-19 vaccination to capture any differences in capacity to receive and integrate data on COVID-19 vaccines versus other vaccines. All VSD sites send data to and receive data from their state IIS. All eight sites (100%) routinely integrate IIS data for COVID-19 vaccines into VSD research studies. Six sites (75%) also routinely integrate all other vaccination data; two sites integrate data from IIS following a reconciliation process, which can result in delays to integration into VSD datasets. COVID-19 vaccines are being administered in a variety of non-traditional settings, where IIS are commonly used as centralized reporting systems. All eight VSD sites receive and integrate COVID-19 vaccine data from IIS, which positions the VSD well for conducting quality assessments of vaccine safety. Efforts to improve the timely receipt of all vaccination data will improve capacity to conduct vaccine safety assessments within the VSD.

Respiratory syncytial virus (RSV) vaccine was recommended for use during pregnancy in September 2023. To assess pregnant persons' intentions to receive and evaluate factors associated with RSV vaccine intentions and uptake. We invited 1999 pregnant persons ≥18 years, between 12 and 30 weeks gestation who had received prenatal care at HealthPartners to complete an online survey during September–November 2023. Our primary outcome was intention to receive RSV vaccine. We also asked respondents about reasons to or not to receive RSV vaccine and intentions to receive other vaccines during pregnancy. We assessed RSV vaccine uptake for patients 32–36 weeks gestation between 10/12/23 (first RSV vaccine in study population) and 2/1/24. We estimated adjusted prevalence ratios (aPR) and 95 % confidence intervals (CI) between responses and intention to receive RSV vaccination and, for those eligible to receive RSV vaccine, adjusted rate ratios (aRR) and 95 % CIs for RSV vaccine uptake. We adjusted aPRs and aRRs for age, race, ethnicity, Medicaid, living with children ≤5 years, and work in healthcare and weighted by inverse probability of survey participation using Poisson regression with robust variance. 455 patients participated (23 % response), 26 % were non-white and/or Hispanic, 46 % lived with children ≤5 years, and 30 % work in healthcare; 65 % intended to receive RSV vaccine during pregnancy. Among 427 eligible respondents, 51 % received RSV vaccine. Factors associated with RSV vaccination intention and uptake included perceived vaccine effectiveness (aPR: 19.47, 95 % CI: 5.82, 65.12; aRR 3.06, 95 % CI: 1.70, 5.51) and a provider recommendation (aPR: 8.04, 95 % CI: 4.23, 15.29; aRR 3.30, 95 % CI: 1.99, 5.48). Among those not planning to receive RSV vaccine, responses suggested safety concerns. Strong recommendations for receiving RSV vaccine during pregnancy from a healthcare provider incorporating information about RSV vaccine safety and effectiveness may increase vaccine uptake.

CDC recommends that all persons aged ≥12 years receive a booster dose of COVID-19 mRNA vaccine ≥5 months after completion of a primary mRNA vaccination series and that immunocompromised persons receive a third primary dose.* Waning of vaccine protection after 2 doses of mRNA vaccine has been observed during the period of the SARS-CoV-2 B.1.617.2 (Delta) variant predominance (1-5), but little is known about durability of protection after 3 doses during periods of Delta or SARS-CoV-2 B.1.1.529 (Omicron) variant predominance. A test-negative case-control study design using data from eight VISION Network sites examined vaccine effectiveness (VE) against COVID-19 emergency department/urgent care (ED/UC) visits and hospitalizations among U.S. adults aged ≥18 years at various time points after receipt of a second or third vaccine dose during two periods: Delta variant predominance and Omicron variant predominance (i.e., periods when each variant accounted for ≥50% of sequenced isolates). Persons categorized as having received 3 doses included those who received a third dose in a primary series or a booster dose after a 2 dose primary series (including the reduced-dosage Moderna booster). The VISION Network analyzed 241,204 ED/UC encounters** and 93,408 hospitalizations across 10 states during August 26, 2021-January 22, 2022. VE after receipt of both 2 and 3 doses was lower during the Omicron-predominant than during the Delta-predominant period at all time points evaluated. During both periods, VE after receipt of a third dose was higher than that after a second dose; however, VE waned with increasing time since vaccination. During the Omicron period, VE against ED/UC visits was 87% during the first 2 months after a third dose and decreased to 66% among those vaccinated 4-5 months earlier; VE against hospitalizations was 91% during the first 2 months following a third dose and decreased to 78% ≥4 months after a third dose. For both Delta- and Omicron-predominant periods, VE was generally higher for protection against hospitalizations than against ED/UC visits. All eligible persons should remain up to date with recommended COVID-19 vaccinations to best protect against COVID-19-associated hospitalizations and ED/UC visits.

Disparities in COVID-19 vaccination rates by race and ethnicity are well documented. Less is known about primary language and COVID-19 vaccine uptake. To describe the time to COVID-19 primary series vaccination and booster doses by primary language and country of origin. This retrospective cohort study included patients aged 6 months or older with at least 1 health encounter from July 1, 2019, to June 30, 2023, at a single health care system serving patients across Minnesota and western Wisconsin. Primary language and country of origin documented in the electronic health record. Three COVID-19 vaccine coverage outcomes were evaluated: (1) primary series (1 Ad26.COV.S vaccine or 2 mRNA COVID-19 vaccines), (2) first-generation booster (primary series Ad26.COV.S vaccine plus 1 Ad26.COV.S or mRNA COVID-19 vaccine at least 2 months after the second dose or primary series mRNA vaccine plus 1 mRNA vaccine at least 5 months after the second dose), and (3) bivalent booster. Vaccine coverage was described by patient characteristics. Associations of primary language, race and ethnicity, and other patient characteristics with COVID-19 vaccine uptake were evaluated using time-to-event analysis in multivariable Cox proportional hazards regression models, and adjusted hazard ratios (AHRs) with 95% CIs were reported. There were 1 001 235 patients included (53.7% female). Most patients reported English as a primary language (94.1%) and were born in the US (91.8%). Primary series coverage was 63.7%; first-generation booster coverage, 64.4%; and bivalent booster coverage, 39.5%. Coverage for all outcomes was lower among those with a non-English primary language compared with English as the primary language (56.9% vs 64.1% for primary series; 47.5% vs 65.3% for first-generation booster; 26.2% vs 40.3% for bivalent booster). Those with a non-English primary language had lower COVID-19 vaccine uptake for the primary series (AHR, 0.85; 95% CI, 0.84-0.86), first-generation booster (AHR, 0.74; 95% CI, 0.73-0.75), and bivalent booster (AHR, 0.65; 95% CI, 0.64-0.67) compared with patients with English as their primary language. Non-US-born patients had higher primary series uptake compared with US-born patients (AHR, 1.19; 95% CI, 1.18-1.20) but similar first-generation booster (AHR, 1.01; 95% CI, 0.99-1.02) and bivalent booster (AHR, 1.00; 95% CI, 0.98-1.02) uptake. In this retrospective cohort study, patients with a non-English primary language had both lower coverage and delays in receiving COVID-19 vaccines compared with those with English as their primary language. Reporting on language may identify health disparities that can be addressed with language-specific interventions.

An increased risk of chorioamnionitis in people receiving tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine during pregnancy has been reported. The importance of this association is unclear as additional study has not demonstrated increased adverse infant outcomes associated with Tdap vaccination in pregnancy. We conducted a retrospective observational cohort study of pregnant people ages 15–49 years with singleton pregnancies ending in live birth who were members of 8 Vaccine Safety Datalink (VSD) sites during October 2016–September 2018. We used a time-dependent covariate Cox model with stabilized inverse probability weights applied to evaluate associations between Tdap vaccination during pregnancy and chorioamnionitis and preterm birth outcomes. We used Poisson regression with robust variance with stabilized inverse probability weights applied to evaluate the association of Tdap vaccination with adverse infant outcomes. We performed medical record reviews on a random sample of patients with ICD-10-CM-diagnosed chorioamnionitis to determine positive predictive values (PPV) of coded chorioamnionitisfor “probable clinical chorioamnionitis,” “possible clinical chorioamnionitis,” or “histologic chorioamnionitis.” We included 118,211 pregnant people; 103,258 (87%) received Tdap vaccine during pregnancy; 8098 (7%) were diagnosed with chorioamnionitis. The adjusted hazard ratio for chorioamnionitis in the Tdap vaccine-exposed group compared to unexposed was 0.96 (95% CI 0.90–1.03). There was no association between Tdap vaccine and preterm birth or adverse infant outcomes associated with chorioamnionitis. Chart reviews were performed for 528 pregnant people with chorioamnionitis. The PPV for clinical (probable or possible clinical chorioamnionitis) was 48% and 59% for histologic chorioamnionitis. The PPV for the combined outcome of clinical or histologic chorioamnionitis was 81%. Tdap vaccine exposure during pregnancy was not associated with chorioamnionitis, preterm birth, or adverse infant outcomes. ICD-10 codes for chorioamnionitis lack specificity for clinical chorioamnionitis and should be a recognized limitation when interpreting results.