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ABSTRACTEmerging SARS-CoV-2 sublineages continue to cause serious COVID-19 disease, but most individuals have not received any COVID-19 vaccine for >1 year. Assessment of long-term effectiveness of bivalent COVID-19 vaccines against circulating sublineages is important to inform the potential need for vaccination with updated vaccines. In this test-negative study at Kaiser Permanente Southern California, sequencing-confirmed BA.4/BA.5- or XBB-related SARS-CoV-2-positive cases (September 1, 2022 to June 30, 2023), were matched 1:3 to SARS-CoV-2-negative controls. We assessed mRNA-1273 bivalent relative (rVE) and absolute vaccine effectiveness (VE) compared to ≥2 or 0 doses of original monovalent vaccine, respectively. The rVE analysis included 20,966 cases and 62,898 controls. rVE (95%CI) against BA.4/BA.5 at 14–60 days and 121–180 days was 52.7% (46.9–57.8%) and 35.5% (−2.8–59.5%) for infection, and 59.3% (49.7–67.0%) and 33.2% (−28.2–68.0%) for Emergency Department/Urgent Care (ED/UC) encounters. For BA.4/BA.5-related hospitalizations, rVE was 71.3% (44.9–85.1%) and 52.0% (−1.2–77.3%) at 14–60 days and 61–120 days, respectively. rVE against XBB at 14–60 days and 121–180 days was 48.8% (33.4–60.7%) and −3.9% (−18.1–11.3%) for infection, 70.7% (52.4–82.0%) and 15.7% (−6.0–33.2%) for ED/UC encounters, and 87.9% (43.8–97.4%) and 57.1% (17.0–77.8%) for hospitalization. VE and subgroup analyses (age, immunocompromised status, previous SARS-CoV-2 infection) results were similar to rVE analyses. rVE of mRNA-1273 bivalent vaccine against BA.4/BA.5 and XBB infections, ED/UC encounters, and hospitalizations waned over time. Periodic revaccination with vaccines targeting emerging variants may be important in reducing COVID-19 morbidity and mortality.

Abstract COVID-19 vaccinations protect against severe illness and death, but associations with post-COVID conditions (PCC) are less clear. We aimed to evaluate the association between prior COVID-19 vaccination and new-onset PCC among individuals with SARS-CoV-2 infection across eight large healthcare systems in the United States. This retrospective matched cohort study used electronic health records (EHR) from patients with SARS-CoV-2 positive tests during March 2021-February 2022. Vaccinated and unvaccinated COVID-19 cases were matched on location, test date, severity of acute infection, age, and sex. Vaccination status was ascertained using EHR and integrated data on externally administered vaccines. Adjusted relative risks (RRs) were obtained from Poisson regression. PCC was defined as a new diagnosis in one of 13 PCC categories 30 days to 6 months following a positive SARS-CoV-2 test. The study included 161,531 vaccinated COVID-19 cases and 161,531 matched unvaccinated cases. Compared to unvaccinated cases, vaccinated cases had a similar or lower risk of all PCC categories except mental health disorders (RR: 1.06, 95% CI: 1.02–1.10). Vaccination was associated with ≥10% lower risk of sensory (RR: 0.90, 0.86–0.95), circulatory (RR: 0.88, 0.83–0.94), blood and hematologic (RR: 0.79, 0.71–0.89), skin and subcutaneous (RR: 0.69, 0.66–0.72), and non-specific COVID-19 related disorders (RR: 0.53, 0.51–0.56). In general, associations were stronger at younger ages but mostly persisted regardless of SARS-CoV-2 variant period, receipt of ≥3 vs. 1–2 vaccine doses, or time since vaccination. Pre-infection vaccination was associated with reduced risk of several PCC outcomes and hence may decrease the long-term consequences of COVID-19.

Background Adverse events following mRNA COVID-19 vaccines, including herpes zoster (HZ), have been reported. We conducted a cohort study to evaluate the association between mRNA COVID-19 vaccination and subsequent HZ at Kaiser Permanente Southern California (KPSC). Research design and methods The vaccinated cohort consisted of KPSC members who received their first dose of mRNA COVID-19 vaccine (mRNA-1273 and BNT162b2) during 12/2020–05/2021 and were matched to unvaccinated individuals on age and sex. Incident HZ cases occurring within 90 days of follow-up were identified by diagnosis codes and antiviral medications. Cox proportional hazards models estimated adjusted hazard ratios (aHR), comparing HZ incidence between the vaccinated and unvaccinated cohorts. Results Cohort included 1,052,362 mRNA-1273 recipients, 1,055,461 BNT162b2 recipients, and 1,020,334 comparators. Compared to unvaccinated individuals, aHR for HZ up to 90 days after the second dose of mRNA-1273 and BNT162b2 was 1.14 (1.05–1.24) and 1.12 (1.03–1.22), respectively. In those aged ≥50 years not vaccinated with zoster vaccine, aHR was also increased after the second dose of mRNA-1273 (1.18 [1.06–1.33]) and BNT162b2 (1.15 [1.02–1.29]) vaccine vs. unvaccinated individuals. Conclusions Our findings suggest a potential increased risk of HZ after a second dose of mRNA vaccines, potentially driven by the increased risk in individuals aged ≥50 years without history of zoster vaccination.

Abstract The bivalent (original and Omicron BA.4/BA.5) mRNA-1273 COVID-19 vaccine was authorized to offer broader protection against COVID-19. We conducted a matched cohort study to evaluate the effectiveness of the bivalent vaccine in preventing hospitalization for COVID-19 (primary outcome) and medically attended SARS-CoV-2 infection and hospital death (secondary outcomes). Compared to individuals who did not receive bivalent mRNA vaccination but received ≥2 doses of any monovalent mRNA vaccine, the relative vaccine effectiveness (rVE) against hospitalization for COVID-19 was 70.3% (95% confidence interval, 64.0%–75.4%). rVE was consistent across subgroups and not modified by time since last monovalent dose or number of monovalent doses received. Protection was durable ≥3 months after the bivalent booster. rVE against SARS-CoV-2 infection requiring emergency department/urgent care and against COVID-19 hospital death was 55.0% (50.8%–58.8%) and 82.7% (63.7%–91.7%), respectively. The mRNA-1273 bivalent booster provides additional protection against hospitalization for COVID-19, medically attended SARS-CoV-2 infection, and COVID-19 hospital death.

In this study, the authors estimate the effectiveness of the mRNA-1273 (Moderna) vaccine for Omicron subvariants using data from the USA on ~31,000 cases and ~92,000 matched controls. They find that effectiveness against infection waned rapidly after third and fourth doses, but effectiveness against hospitalization remained high.

Abstract Introduction This observational retrospective matched cohort study evaluated the safety of a prenatal tetanus, diphtheria, acellular pertussis (Tdap) vaccination, Boostrix. We previously reported on the risk of maternal and neonatal outcomes; here we report on the risk of congenital anomalies in infants at birth through 6 months of age. Methods The study included pregnant Kaiser Permanente Southern California members. Women who received the Tdap vaccine on or after the 27th week of pregnancy between January 2018 and January 2019 were matched to women who were pregnant between January 2012 and December 2014 and were not vaccinated with Tdap during pregnancy. Unadjusted and adjusted relative risks (aRRs) with 95% confidence intervals were estimated by Poisson regression. Quantitative secular trend analyses, from 2011 to 2017, were conducted on congenital anomalies with a statistically significant aRR > 1. Results The analysis consisted of 16,350 and 16,088 live-born infants in the Tdap-exposed and unexposed cohorts, respectively. Of the 14 congenital anomaly body systems evaluated, 8 (eye, ear/face/neck, respiratory, upper gastrointestinal, genital, renal, musculoskeletal, integument) had statistically significant elevated aRRs, with point estimates ranging from 1.17 to 2.02. The observed elevated aRRs were consistent with their respective secular increases over time. Conclusion Cautious interpretation of these findings is warranted as these increases may have resulted from improved identification and diagnosis. Furthermore, the biological plausibility of an association between maternal vaccine exposure in the third trimester of pregnancy and birth defects is low. The overall study findings support the safety of maternal immunization with Boostrix during the third trimester of pregnancy. Trial Registration ClinicalTrials.gov identifier, NCT03463577.

Background: Measles, mumps, and rubella vaccine (MMR) is routinely administered to children; however, adolescents and adults may receive MMR for various reasons. Safety studies in adolescents and adults are limited. We report on safety of MMR in this age group in the Vaccine Safety Datalink. Methods: We included adolescents (aged 9–17 years) and adults (aged ≥ 18 years) who received ≥ 1 dose of MMR from January 1, 2010–December 31, 2018. Pre-specified outcomes were identified by diagnosis codes. Clinically serious outcomes included anaphylaxis, encephalitis/myelitis, Guillain-Barré syndrome, immune thrombocytopenia, meningitis, and seizure. Non-serious outcomes were allergic reaction, arthropathy, fever, injection site reaction, lymphadenopathy, non-specific reaction, parotitis, rash, and syncope. All serious outcomes underwent medical record review. Outcome-specific incidence was calculated in pre-defined post-vaccination windows. A self-controlled risk interval design was used to determine the relative risk of each outcome in a risk window after vaccination compared to a more distal control window. Results: During the study period, 276,327 MMR doses were administered to adolescents and adults. Mean age of vaccinees was 34.8 years; 65.8 % were female; 53.2 % of doses were administered simultaneously with ≥ 1 other vaccine. Serious outcomes were rare, with incidence ≤ 6 per 100,000 doses for each outcome assessed, and none had a significant elevation in incidence during the risk window compared to the control window. Incidence of non-serious outcomes per 100,000 doses ranged from 3.4 for parotitis to 263.0 for arthropathy. Other common outcomes included injection site reaction and rash (157.0 and 112.9 per 100,000 doses, respectively). Significantly more outcomes were observed during the risk window compared to the control window for all non-serious outcomes except parotitis. Some variability was observed by sex and age group. Conclusion: Serious outcomes after MMR are rare in adolescents and adults, but vaccinees should be counseled regarding anticipated local and systemic non-serious adverse events.

Two quadrivalent meningococcal conjugate vaccines (MenACWY) that prevent invasive meningococcal disease caused by N. meningitidis serogroups A, C, Y, and W have been licensed in the U.S. in the past 10–15 years. We systematically reviewed published studies conducted in the U.S. to evaluate the real-world safety evidence of meningococcal conjugate vaccines. We performed a literature search in PubMed of publications from 01/01/2005 to 02/29/2020 and identified 18 studies meeting inclusion criteria. Populations included high-risk persons aged 2 months to 10 years, adolescents/adults aged ≥11 years, pregnant populations, and hematopoietic cell transplant recipients. We extracted information about study setting, study design, exposure, outcomes, comparison group, follow-up/look back period, study population, sample size, available demographic/indication information, results, key conclusion, and reference. These published studies found no new significant safety concerns related to MenACWY. Consideration for future research includes a post-licensure safety evaluation of a new MenACWY product approved in April 2020.

Summary: Background: Phase 3 trials found mRNA-1273 was highly effective in preventing COVID-19. We conducted a prospective cohort study at Kaiser Permanente Southern California (KPSC) to determine the real-world vaccine effectiveness (VE) of mRNA-1273 in preventing COVID-19 infection and severe disease. Methods: For this planned interim analysis, individuals aged ≥18 years receiving 2 doses of mRNA-1273 ≥24 days apart (18/12/2020-31/03/2021) were 1:1 matched to randomly selected unvaccinated individuals by age, sex, and race/ethnicity, with follow-up through 30/06/2021. Outcomes were COVID-19 infection (SARS-CoV-2 positive molecular test or COVID-19 diagnosis code) or severe disease (COVID-19 hospitalization and COVID-19 hospital death). Adjusted hazard ratios (aHR) and confidence intervals (CI) for COVID-19 outcomes comparing vaccinated and unvaccinated individuals were estimated by Cox proportional hazards models accounting for multiple comparisons. Adjusted VE was calculated as (1-aHR)x100. Whole genome sequencing was performed on SARS-CoV-2 positive specimens from the KPSC population. Findings: This analysis included 352,878 recipients of 2 doses of mRNA-1273 matched to 352,878 unvaccinated individuals. VE (99·3% CI) against COVID-19 infection was 87·4% (84·8–89·6%). VE against COVID-19 hospitalization and hospital death was 95·8% (90·7–98·1%) and 97·9% (66·9-99·9%), respectively. VE was higher against symptomatic (88·3% [98·3% CI: 86·1–90·2%]) than asymptomatic COVID-19 (72·7% [53·4–84·0%]), but was generally similar across age, sex, and racial/ethnic subgroups. VE among individuals with history of COVID-19 ranged from 8·2–33·6%. The most prevalent variants were Alpha (41·6%), Epsilon (17·5%), Delta (11·5%), and Gamma (9·1%), with Delta increasing to 54·0% of variants by June 2021. Interpretation: These interim results provide reassuring evidence of the VE of 2 doses of mRNA-1273 across age, sex, and racial/ethnic subgroups, and against asymptomatic and symptomatic COVID-19, and severe COVID-19 outcomes. Among individuals with history of COVID-19, mRNA-1273 vaccination may offer added protection beyond immunity acquired from prior infection. Longer follow-up is needed to fully evaluate VE of mRNA-1273 against emerging SARS-CoV-2 variants. Funding: Moderna Inc.

Post-licensure vaccine safety studies are essential to identify adverse events that may not have been detected in pre-licensure clinical trials and to address questions that arose during the pre-licensure phase. These studies are increasingly conducted using real-world data collected as part of routine health care delivery. However, design of post-licensure vaccine safety studies involves many pragmatic and scientific decisions, which must be made while balancing diverse stakeholder opinions. Challenges include selecting exposure and comparison groups, deciding on the most appropriate outcome, determining sample size and length of follow-up time, and other analytic considerations. As an example of this process and to inform other post-licensure vaccine safety studies in real-world settings, we discuss our experience with design of an FDA-required Phase 4 post-licensure safety study of a hepatitis B vaccine in a large integrated health care organization in the United States.

Limited safety data are available on inadvertent exposure to quadrivalent human papillomavirus vaccine (4vHPV) during pregnancy. We conducted a descriptive observational postlicensure safety surveillance study in Kaiser Permanente Southern California and Northern California to assess congenital anomaly and miscarriage among pregnancies exposed to 4vHPV. Using electronic medical records, we identified women who received a dose of 4vHPV between August 2006 and March 2008 within 30 days preconception or any time during a possible pregnancy. A broad algorithm was developed using diagnostic and procedure codes and laboratory tests to identify pregnancy, congenital anomalies, and miscarriages. Medical records of all potential congenital anomaly cases and a random sample of 100 potential miscarriage cases were reviewed to confirm pregnancy exposure and diagnosis. Results were reviewed by an independent Safety Review Committee (SRC). Among the population of 189,629 females who received at least one dose of 4vHPV during the study period, 2,678 females were identified as possibly having a 4vHPV-exposed pregnancy. Among 170 potential congenital anomalies identified, 44 (26%) were found to be both 4vHPV-exposed and confirmed congenital anomaly cases. Among the 633 potential miscarriages identified, the records of a random sample of 100 cases were reviewed, and 9 cases (9%) were confirmed as 4vHPV-exposed miscarriages. The SRC noted no safety signal for congenital anomaly or miscarriage associated with 4vHPV exposure during pregnancy. The rate of major congenital anomaly (3.6%) was in the range of background estimates from the literature. There was no apparent pattern of timing of 4vHPV exposure among 4vHPV-exposed miscarriages.

Background: Studies have investigated a possible association between family history of HZ and the occurrence of HZ. However, the results were inconclusive and susceptible to bias. We evaluated this association in an elderly population. Methods: The matched case-control study conducted at Kaiser Permanente Southern California in 2012-2015 included 656 incident HZ patients ≥60 whose skin lesion tested positive for varicella zoster virus by polymerase chain reaction. Half of the HZ patients were vaccinated with zoster vaccine as achieved by stratified sampling. The controls were randomly selected and 1:1 matched to the cases on sex, age (±1 year), and zoster vaccination (±3 months of the case’s vaccination date). Conditional logistic regression was used to estimate the odds ratio (OR) and 95% confidence interval (CI). Results: Having any blood relative with a history of HZ was associated with a slightly increased risk of HZ (adjusted OR = 1.37, 95% CI 1.05–1.79). The adjusted OR associated with having one and two categories of first-degree blood relatives with a history of HZ was 1.30 (95% CI: 0.97–1.73) and 2.53 (95% CI: 1.17–5.44), respectively. Conclusions: Our results suggested a weak association between the development of HZ and a positive family history of HZ among the elderly population.

HepB-CpG is a licensed adjuvanted two-dose hepatitis B vaccine for adults, with limited data on exposure during pregnancy. We assessed the risk of pregnancy outcomes among individuals who received HepB-CpG or the 3-dose HepB-alum vaccine ≤28 d prior to conception or during pregnancy at Kaiser Permanente Southern California (KPSC). The pregnancy cohort included KPSC members aged ≥18 y who received ≥1 dose of hepatitis B vaccine (HepB-CpG or HepB-alum) at KPSC outpatient family or internal medicine departments from August 2018 to November 2020. We followed these individuals through electronic health records from the vaccination date until the end of pregnancy, KPSC health plan disenrollment, or death, whichever came first. Among 81 and 125 eligible individuals who received HepB-CpG and HepB-alum, respectively, live births occurred in 84% and 74%, spontaneous abortion occurred in 7% and 17% (adjusted relative risk [aRR] 0.40, 95% CI: 0.16–1.00), and preterm birth occurred in 15% and 14% of liveborn infants (aRR 0.97, 95% CI 0.47–1.99). No major birth defects were identified through 6 months of age. The study found no evidence of adverse pregnancy outcomes for recipients of HepB-CpG in comparison to HepB-alum.

Abstract BackgroundDiagnosis codes and prescription data are used in algorithms to identify postherpetic neuralgia (PHN), a debilitating complication of herpes zoster (HZ). Because of the questionable accuracy of codes and prescription data, manual chart review is sometimes used to identify PHN in electronic health records (EHRs), which can be costly and time-consuming. ObjectiveThis study aims to develop and validate a natural language processing (NLP) algorithm for automatically identifying PHN from unstructured EHR data and to compare its performance with that of code-based methods. MethodsThis retrospective study used EHR data from Kaiser Permanente Southern California, a large integrated health care system that serves over 4.8 million members. The source population included members aged ≥50 years who received an incident HZ diagnosis and accompanying antiviral prescription between 2018 and 2020 and had ≥1 encounter within 90‐180 days of the incident HZ diagnosis. The study team manually reviewed the EHR and identified PHN cases. For NLP development and validation, 500 and 800 random samples from the source population were selected, respectively. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), F-score, and Matthews correlation coefficient (MCC) of NLP and the code-based methods were evaluated using chart-reviewed results as the reference standard. ResultsThe NLP algorithm identified PHN cases with a 90.9% sensitivity, 98.5% specificity, 82% PPV, and 99.3% NPV. The composite scores of the NLP algorithm were 0.89 (F-score) and 0.85 (MCC). The prevalences of PHN in the validation data were 6.9% (reference standard), 7.6% (NLP), and 5.4%‐13.1% (code-based). The code-based methods achieved a 52.7%‐61.8% sensitivity, 89.8%‐98.4% specificity, 27.6%‐72.1% PPV, and 96.3%‐97.1% NPV. The F-scores and MCCs ranged between 0.45 and 0.59 and between 0.32 and 0.61, respectively. ConclusionsThe automated NLP-based approach identified PHN cases from the EHR with good accuracy. This method could be useful in population-based PHN research.

BackgroundThe potential association between bivalent COVID-19 vaccination and ischemic stroke remains uncertain, despite several studies conducted thus far. ObjectiveThis study aimed to evaluate the risk of ischemic stroke following bivalent COVID-19 vaccination during the 2022-2023 season. MethodsA self-controlled case series study was conducted among members aged 12 years and older who experienced ischemic stroke between September 1, 2022, and March 31, 2023, in a large health care system. Ischemic strokes were identified using International Classification of Diseases, Tenth Revision codes in emergency departments and inpatient settings. Exposures were Pfizer-BioNTech or Moderna bivalent COVID-19 vaccination. Risk intervals were prespecified as 1-21 days and 1-42 days after bivalent vaccination; all non–risk-interval person-time served as the control interval. The incidence of ischemic stroke was compared in the risk interval and control interval using conditional Poisson regression. We conducted overall and subgroup analyses by age, history of SARS-CoV-2 infection, and coadministration of influenza vaccine. When an elevated risk was detected, we performed a chart review of ischemic strokes and analyzed the risk of chart-confirmed ischemic stroke. ResultsWith 4933 ischemic stroke events, we found no increased risk within the 21-day risk interval for the 2 vaccines and by subgroups. However, risk of ischemic stroke was elevated within the 42-day risk interval among individuals aged younger than 65 years with coadministration of Pfizer-BioNTech bivalent and influenza vaccines on the same day; the relative incidence (RI) was 2.13 (95% CI 1.01-4.46). Among those who also had a history of SARS-CoV-2 infection, the RI was 3.94 (95% CI 1.10-14.16). After chart review, the RIs were 2.34 (95% CI 0.97-5.65) and 4.27 (95% CI 0.97-18.85), respectively. Among individuals aged younger than 65 years who received Moderna bivalent vaccine and had a history of SARS-CoV-2 infection, the RI was 2.62 (95% CI 1.13-6.03) before chart review and 2.24 (95% CI 0.78-6.47) after chart review. Stratified analyses by sex did not show a significantly increased risk of ischemic stroke after bivalent vaccination. ConclusionsWhile the point estimate for the risk of chart-confirmed ischemic stroke was elevated in a risk interval of 1-42 days among individuals younger than 65 years with coadministration of Pfizer-BioNTech bivalent and influenza vaccines on the same day and among individuals younger than 65 years who received Moderna bivalent vaccine and had a history of SARS-CoV-2 infection, the risk was not statistically significant. The potential association between bivalent vaccination and ischemic stroke in the 1-42–day analysis warrants further investigation among individuals younger than 65 years with influenza vaccine coadministration and prior SARS-CoV-2 infection. Furthermore, the findings on ischemic stroke risk after bivalent COVID-19 vaccination underscore the need to evaluate monovalent COVID-19 vaccine safety during the 2023-2024 season.

BackgroundUnderstanding 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. ObjectiveThis 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. MethodsWe 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. ResultsThe 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. ConclusionsTelehealth 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.

BackgroundCOVID-19 vaccination is crucial in combating the COVID-19 pandemic. Messenger RNA COVID-19 vaccines were initially authorized as a 2-dose primary series and have been widely used in the United States; completing the 2-dose primary series offers protection against infection, severe illness, and death. Understanding the risk factors for not completing the 2-dose primary series is critical to evaluate COVID-19 vaccination programs and promote completion of the 2-dose primary series. ObjectiveThis study examined potential risk factors for not completing a 2-dose primary series of mRNA COVID-19 vaccination. MethodsWe conducted a retrospective cohort study among members aged ≥18 years from a large integrated health care system, Kaiser Permanente Southern California, from December 14, 2020, to June 30, 2022. Noncompletion of the 2-dose primary series was defined as not completing the second dose within 6 months after receipt of the first dose. Crude noncompletion rates were estimated overall and by demographic characteristics, health care use patterns, comorbidity, and community-level socioeconomic factors. A Poisson regression model was fit to examine associations of individual-level and community-level risk factors with noncompletion of the 2-dose primary series. ResultsAmong 2.5 million recipients of ≥1 dose of mRNA COVID-19 vaccines, 3.3% (n=81,202) did not complete the second dose within 6 months. Members aged 25-44 years, 65-74 years, and ≥75 years were less likely to not complete the 2-dose primary series than those aged 18-24 years, while members aged 45-64 years were more likely to not complete the 2-dose primary series (adjusted risk ratio [aRR] 1.13, 95% CI 1.10-1.15). Male sex was associated with a higher risk of noncompletion (aRR 1.17, 95% CI 1.15-1.19). Hispanic and non-Hispanic Black race/ethnicity were associated with a lower risk of noncompletion (range aRR 0.78-0.91). Having Medicaid and prior influenza vaccination were associated with a higher risk of noncompletion. Having SARS-CoV-2 infection, experiencing an adverse event, or having an inpatient and emergency department visit during the minimum recommended dose intervals were associated with a higher risk of not completing the 2-dose primary series (aRR 1.98, 95% CI 1.85-2.12; 1.99, 95% CI 1.43-2.76; and 1.85, 95% CI 1.77-1.93, respectively). Those who received the first dose after June 30, 2021, were more likely to not complete the 2-dose primary series within 6 months of receipt of the first dose. ConclusionsDespite limitations such as being a single-site study and the inability to consider social factors such as employment and vaccine attitudes, our study identified several risk factors for not completing a 2-dose primary series of mRNA vaccination, including being male; having Medicaid coverage; and experiencing SARS-CoV-2 infection, adverse events, or inpatient and emergency department visits during the minimum recommended dose intervals. These findings can inform future efforts in developing effective strategies to enhance vaccination coverage and improve the completion rate of necessary doses.

BackgroundShoulder injury related to vaccine administration (SIRVA) accounts for more than half of all claims received by the National Vaccine Injury Compensation Program. However, due to the difficulty of finding SIRVA cases in large health care databases, population-based studies are scarce. ObjectiveThe goal of the research was to develop a natural language processing (NLP) method to identify SIRVA cases from clinical notes. MethodsWe conducted the study among members of a large integrated health care organization who were vaccinated between April 1, 2016, and December 31, 2017, and had subsequent diagnosis codes indicative of shoulder injury. Based on a training data set with a chart review reference standard of 164 cases, we developed an NLP algorithm to extract shoulder disorder information, including prior vaccination, anatomic location, temporality and causality. The algorithm identified 3 groups of positive SIRVA cases (definite, probable, and possible) based on the strength of evidence. We compared NLP results to a chart review reference standard of 100 vaccinated cases. We then applied the final automated NLP algorithm to a broader cohort of vaccinated persons with a shoulder injury diagnosis code and performed manual chart confirmation on a random sample of NLP-identified definite cases and all NLP-identified probable and possible cases. ResultsIn the validation sample, the NLP algorithm had 100% accuracy for identifying 4 SIRVA cases and 96 cases without SIRVA. In the broader cohort of 53,585 vaccinations, the NLP algorithm identified 291 definite, 124 probable, and 52 possible SIRVA cases. The chart-confirmation rates for these groups were 95.5% (278/291), 67.7% (84/124), and 17.3% (9/52), respectively. ConclusionsThe algorithm performed with high sensitivity and reasonable specificity in identifying positive SIRVA cases. The NLP algorithm can potentially be used in future population-based studies to identify this rare adverse event, avoiding labor-intensive chart review validation.

BackgroundWe conducted a prospective cohort study at Kaiser Permanente Southern California to study the vaccine effectiveness (VE) of mRNA-1273 over time and during the emergence of the Delta variant.MethodsThe cohort for this planned interim analysis consisted of individuals aged ≥18 years receiving 2 doses of mRNA-1273 through June 2021, matched 1:1 to randomly selected unvaccinated individuals by age, sex, and race/ethnicity, with follow-up through September 2021. Outcomes were SARS-CoV-2 infection, and COVID-19 hospitalization and hospital death. Cox proportional hazards models were used to estimate adjusted hazard ratios (aHR) with 95% confidence intervals (CIs) comparing outcomes in the vaccinated and unvaccinated groups. Adjusted VE (%) was calculated as (1-aHR)x100. HRs and VEs were also estimated for SARS-CoV-2 infection by age, sex, race/ethnicity, and during the Delta period (June-September 2021). VE against SARS-CoV-2 infection and COVID-19 hospitalization was estimated at 0-Results927,004 recipients of 2 doses of mRNA-1273 were matched to 927,004 unvaccinated individuals. VE (95% CI) was 82.8% (82.2-83.3%) against SARS-CoV-2 infection, 96.1% (95.5-96.6%) against COVID-19 hospitalization, and 97.2% (94.8-98.4%) against COVID-19 hospital death. VE against SARS-CoV-2 infection was similar by age, sex, and race/ethnicity, and was 86.5% (84.8-88.0%) during the Delta period. VE against SARS-CoV-2 infection decreased from 88.0% at 0-ConclusionsThese interim results provide continued evidence for protection of 2 doses of mRNA-1273 against SARS-CoV-2 infection over 8 months post-vaccination and during the Delta period, and against COVID-19 hospitalization and hospital death.

BackgroundDramatic decreases in outpatient visits and sudden increases in telehealth visits were observed during the COVID-19 pandemic, but it was unclear whether these changes differed by patient demographics and socioeconomic status. ObjectiveThis study aimed to assess the impact of the pandemic on in-person outpatient and telehealth visits (telephone and video) by demographic characteristics and household income in a diverse population. MethodsWe calculated weekly rates of outpatient and telehealth visits by age, sex, race/ethnicity, and neighborhood-level median household income among members of Kaiser Permanente Southern California (KPSC) from January 5, 2020, to October 31, 2020, and the corresponding period in 2019. We estimated the percentage change in visit rates during the early pandemic period (March 22 to April 25, 2020) and the late pandemic period (October 4 to October 31, 2020) from the prepandemic period (January 5 to March 7, 2020) in Poisson regression models for each subgroup while adjusting for seasonality using 2019 data. We examined if the changes in visit rates differed by subgroups statistically by comparing their 95% CIs. ResultsAmong 4.56 million KPSC members enrolled in January 2020, 15.0% (n=682,947) were ≥65 years old, 51.5% (n=2,345,020) were female, 39.4% (n=1,795,994) were Hispanic, and 7.7% (n=350,721) lived in an area of median household income

Objectives: We examined the trends and correlates of quadrivalent human papillomavirus vaccine (HPV4) initiation in insured boys during the periods before and after routine use recommendation., Methods: We grouped data from electronic medical records of boys aged 9 to 17 years from the Kaiser Permanente Southern California prepaid health plan into 3 open cohorts: permissive use: 2009 to 2010; anal cancer indication added: 2010 to 2011; and routine use: 2011 to 2013. We estimated adjusted risk ratios (ARRs) between demographics and vaccination initiation using Poisson regression., Results: HPV4 initiation increased across cohorts--1.6%, 3.4%, and 18.5%--with the greatest increase among boys aged 11 to 12 years in cohort 3. Initiation was associated with receiving influenza vaccination in the previous year in all cohorts (cohort 3: ARR = 1.48; 95% confidence interval [CI] = 1.46, 1.51) and with non-White race/ethnicity following routine recommendation (cohort 3, non-Hispanic Black: ARR = 1.18; 95% CI = 1.08, 1.30; Hispanic: ARR = 1.23; 95% CI = 1.17, 1.29; Asian/Pacific Islanders: ARR = 1.16; 95% CI = 1.11, 1.20)., Conclusions: Routine use recommendation increased the uptake of HPV4 in boys. System-level interventions to encourage providers to routinely recommend HPV4 vaccination may help increase HPV4 uptake in boys.