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There is concern that influenza vaccine effectiveness (VE) may be attenuated by passage in eggs during manufacture. We compared quadrivalent cell-culture vaccine with egg-based vaccines, most of which were trivalent, against influenza A and B during 2017-2018 when A(H3N2) and B/Yamagata (present only in quadrivalent vaccines) predominated. We retrospectively examined risk of PCR-confirmed influenza A and B in members of Kaiser Permanente Northern California aged 4-64 years. We estimated the relative VE (rVE) of cell-culture vaccine versus egg-based vaccines, and the absolute VE (aVE) of each vaccine comparing vaccinated to unvaccinated individuals. Analyses used Cox regression with a calendar timeline, stratified by birth year, and adjusted for demographics, co-morbidities and utilization. One-third (1,016,965/3,053,248) of the population was vaccinated; 932,545 (91.7% of vaccinees) received egg-based and 84,420 (8.3%) received cell-culture vaccines. The rVE against influenza A was 8.0% (95% CI: -10, 23); aVE was 31.7% (CI: 18.7, 42.6) for cell-culture and 20.1% (CI: 14.5, 25.4) for egg-based vaccines. The rVE against influenza B was 39.6% (CI: 27.9, 49.3); aVE was 40.9% (CI: 30, 50.1) for cell-culture and 9.7% (CI 3.5, 15.6) for egg-based trivalent vaccines. Inclusion of the B/Yamagata lineage in the quadrivalent cell-based vaccine provided better protection against influenza B but vaccine effectiveness against influenza A was low for both the cell-culture vaccine and the egg-based vaccines. Improving influenza vaccines requires ongoing comparative vaccine effectiveness monitoring.

The combination DTaP-IPV/Hib vaccine was licensed in the United States in 2008 for children ages 6weeks through 4years with doses administered at 2, 4, 6, and 15–18months of age. The aim of this study was to assess the safety of DTaP-IPV/Hib vaccine routinely administered as part of clinical care to infants at Kaiser Permanente Northern California. This was an observational, retrospective study that included all 2-month-old infants vaccinated with either DTaP-IPV/Hib or another DTaP-containing vaccine. We monitored all subjects for non-elective hospitalizations, emergency department visits and selected outpatient outcomes (seizures, Guillain-Barré Syndrome, encephalopathy, encephalitis, alteration of consciousness, meningitis, hypersensitivity reactions, immune thrombocytopenic purpura, hemolytic anemia, type 1 diabetes, and Kawasaki disease) beginning with their first dose through 6months after a 4th dose or until 24months of age. We calculated incidence rate ratios (IRRs) in the primary analysis by comparing rates of outcomes during the post-vaccination risk interval with rates during a comparison interval more remote from vaccination. Secondary analyses compared outcomes after DTaP-IPV/Hib with those after other DTaP-containing vaccines. We reviewed the medical records of selected outcomes. From October 1, 2008 through July 31, 2010, 14,042 subjects received a first dose of DTaP-IPV/Hib, 13,194 received 2 doses, 12,548 received 3 doses and 6702 received 4 doses. Overall, there were 166 comparisons with significantly elevated IRRs and 165 comparisons with significantly reduced IRRs. Medical record review of outcomes with significantly elevated IRRs in both the primary and secondary analyses did not suggest any relationship with DTaP-IPV/Hib. This study did not detect any safety concerns following DTaP-IPV/Hib and provides reassurance that DTaP-IPV/Hib administered as part of routine care was not associated with unexpected safety risks. ClinicalTrials.gov Identifier: NCT00804284

•Kaiser Permanente Northern California pregnancy database currently includes 859,699 women and 873,753 live birth children.•Approximately 35,000 new births will be added every year.•Database can be used for studies investigating exposure during pregnancy and outcomes in mothers and/or infants.•Tdap vaccination during pregnancy was not associated with infant fever 0–3 days after first dose of DTaP. We describe the establishment of a dynamic database linking mothers to newborns with the goal of studying vaccine safety in both pregnant women and their children and provide results of a study utilizing this database as a proof of concept. All Kaiser Permanente Northern California (KPNC) live births and their mothers were eligible for inclusion in the pregnancy database. We used the medical record number (MRN), a unique identifier, to retrieve information about events that occurred during the pregnancy and at delivery and linked this same MRN to newborns for post-partum follow up. We conducted a retrospective cohort study to evaluate the association between receipt of tetanus, diphtheria and acellular pertussis (Tdap) vaccine during pregnancy and fever 0–3days after the first dose of diphtheria tetanus and acellular pertussis (DTaP) vaccine in the infant. The study included infants who were born at ⩾37weeks gestation from January 1, 2009 – October 1, 2015 and who received their first DTaP vaccine between 6 and 10weeks of age. We utilized diagnostic codes from inpatient, emergency department, outpatient clinics, and telephone calls. We identified fever using ICD 9 code 780.6, recorded temperature ⩾101 degree Fahrenheit, or parental report. The database contained the starting and ending date of each pregnancy and basic demographic characteristics of mothers and infants. There were 859,699 women and 873,753 children in the database as of January 2016. The proof of concept study included 148,699 infants. In a multivariable logistic regression analysis, Tdap vaccination during pregnancy was not associated with infant fever 0–3daysafter first dose of DTaP (adjusted odds ratio=0.92, 95% CI 0.82–1.04). The KPNC pregnancy database can be used for studies investigating exposure during pregnancy and outcomes in mothers and/or infants, particularly monitoring vaccine safety and effectiveness.

Real-world COVID-19 vaccine effectiveness (VE) studies are investigating exposures of increasing complexity accounting for time since vaccination. These studies require methods that adjust for the confounding that arises when morbidities and demographics are associated with vaccination and the risk of outcome events. Methods based on propensity scores (PS) are well-suited to this when the exposure is dichotomous, but present challenges when the exposure is multinomial. This simulation study aimed to investigate alternative methods to adjust for confounding in VE studies that have a test-negative design. Adjustment for a disease risk score (DRS) is compared with multivariable logistic regression. Both stratification on the DRS and direct covariate adjustment of the DRS are examined. Multivariable logistic regression with all the covariates and with a limited subset of key covariates is considered. The performance of VE estimators is evaluated across a multinomial vaccination exposure in simulated datasets. Bias in VE estimates from multivariable models ranged from -5.3% to 6.1% across 4 levels of vaccination. Standard errors of VE estimates were unbiased, and 95% coverage probabilities were attained in most scenarios. The lowest coverage in the multivariable scenarios was 93.7% (95% CI 92.2%-95.2%) and occurred in the multivariable model with key covariates, while the highest coverage in the multivariable scenarios was 95.3% (95% CI 94.0%-96.6%) and occurred in the multivariable model with all covariates. Bias in VE estimates from DRS-adjusted models was low, ranging from -2.2% to 4.2%. However, the DRS-adjusted models underestimated the standard errors of VE estimates, with coverage sometimes below the 95% level. The lowest coverage in the DRS scenarios was 87.8% (95% CI 85.8%-89.8%) and occurred in the direct adjustment for the DRS model. The highest coverage in the DRS scenarios was 94.8% (95% CI 93.4%-96.2%) and occurred in the model that stratified on DRS. Although variation in the performance of VE estimates occurred across modeling strategies, variation in performance was also present across exposure groups. Overall, models using a DRS to adjust for confounding performed adequately but not as well as the multivariable models that adjusted for covariates individually.

In a study over two influenza seasons, a high-dose recombinant influenza vaccine was 15% more effective than a standard-dose vaccine in preventing PCR-confirmed influenza in adults between 50 and 64 years of age.

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%).

Abstract 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. Vaccine effectiveness appears to decrease with time since vaccination. The odds of influenza in remote vaccinees vs recent vaccinees increased by about 16% per 28 days. Influenza vaccination may be more effective if received closer to the start of the influenza season.

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.

•Study of safety of 9-valent HPV vaccine in males and females ages 9 and up.•Most study findings were previously known or unassociated with vaccination.•Reassuring evidence of safety of 9-valent HPV vaccine in routine medical care. The nine-valent human papillomavirus vaccine (HPV9, Gardasil®9) was licensed in the USA in December 2014. This study was a multiyear post-licensure study to assess HPV9 safety following routine administration. This retrospective cohort study compared the risk of emergency department visits and hospitalizations during the interval soon after vaccination with risk during a later interval. Kaiser Permanente Northern California (KPNC) members aged ≥ 9 years who received ≥ 1 HPV9 dose between 10/1/2015–9/30/2017 were included. Outcomes were grouped into predefined diagnostic categories. We compared the odds of events in postvaccination risk intervals (days 0–14, days 1–60) with odds of events during control intervals (days 61–75, days 61–120) using conditional logistic regression. We characterized prespecified events on the day of vaccination (allergic reaction and syncope) and all deaths in the study period. The study included 215,965 individuals receiving ≥ 1 dose of HPV9, of whom 140,628 had no prior HPV vaccination. We observed similar numbers of males and females and racial/ethnic diversity consistent with the underlying population. At first dose median age was 12–13 years and 77% received ≥ 1 concomitant vaccine. Eighteen event categories were significantly elevated, including skin disorders (odds ratio [OR] 1.88, 95% confidence interval [CI] 1.00, 3.53) and ill-defined conditions (OR 1.36, 95% CI 1.13, 1.64; category includes abdominal pain, allergic reactions, syncope, etc.). On review, most findings were previously known, preceded vaccination, or had other causes. Allergic reactions and syncope at vaccination were infrequent but many were potentially related. No deaths (n = 37) were considered related to HPV9 and were consistent with the background rate. We did not identify new safety concerns related to HPV9. The results are consistent with the HPV9 safety profile as established from previous studies/surveillance. European Network of Centres for Pharmacoepidemiology and Pharmacovigilance (EUPAS13151, protocol V503-028).