Temporal Trends in Undervaccination: A Population-Based Cohort Study

INTRODUCTION

Monitoring the trends in undervaccination, including that because of parental vaccine refusal or delay, can inform public health responses directed at improving vaccine confidence and vaccination coverage.

METHODS

A retrospective cohort study was conducted in the Vaccine Safety Datalink. The cohort included all children born in 2004-2017 with ≥3 well-child visits between ages 2 and 23 months. Using electronic health record-based vaccination data, the average days undervaccinated was calculated for each child. Undervaccination patterns were assessed through age 23 months. Temporal trends were inspected for inflection points and were analyzed using linear regression. Nested within the cohort study, a survey was conducted to compare parent reports of vaccine refusal or delay with observed vaccination patterns. Data were analyzed in 2020.

RESULTS

The study cohort consisted of 808,170 children. The percentage of children with average days undervaccinated=0 (fully vaccinated, no delays) rose from a nadir of 47.1% for the birth year 2008 to 68.4% for the birth year 2017 (p_trend<0.001). The percentage with no vaccines rose from 0.35% for the birth year 2004 to 1.28% for the birth year 2017 (p_trend<0.001). Consistent vaccine limiting was observed in 2.04% for the birth year 2017. Omission of measles, mumps, and rubella vaccine peaked at 4.76% in the birth year 2007 and declined thereafter (p_trend<0.001). On the parent survey (response rate 60.2%), a high proportion of parents of the most undervaccinated children reported refusing or delaying vaccines.

CONCLUSIONS

In a 14-year cohort study, vaccination timeliness has improved. However, the small but increasing number of children who received no vaccines by age 23 months warrants additional attention.

Impact of COVID-19-related disruptions to measles, meningococcal A, and yellow fever vaccination in 10 countries

Background

Childhood immunisation services have been disrupted by the COVID-19 pandemic. WHO recommends considering outbreak risk using epidemiological criteria when deciding whether to conduct preventive vaccination campaigns during the pandemic.

Methods

We used two to three models per infection to estimate the health impact of 50% reduced routine vaccination coverage in 2020 and delay of campaign vaccination from 2020 to 2021 for measles vaccination in Bangladesh, Chad, Ethiopia, Kenya, Nigeria, and South Sudan, for meningococcal A vaccination in Burkina Faso, Chad, Niger, and Nigeria, and for yellow fever vaccination in the Democratic Republic of Congo, Ghana, and Nigeria. Our counterfactual comparative scenario was sustaining immunisation services at coverage projections made prior to COVID-19 (i.e. without any disruption).

Results

Reduced routine vaccination coverage in 2020 without catch-up vaccination may lead to an increase in measles and yellow fever disease burden in the modelled countries. Delaying planned campaigns in Ethiopia and Nigeria by a year may significantly increase the risk of measles outbreaks (both countries did complete their supplementary immunisation activities (SIAs) planned for 2020). For yellow fever vaccination, delay in campaigns leads to a potential disease burden rise of >1 death per 100,000 people per year until the campaigns are implemented. For meningococcal A vaccination, short-term disruptions in 2020 are unlikely to have a significant impact due to the persistence of direct and indirect benefits from past introductory campaigns of the 1- to 29-year-old population, bolstered by inclusion of the vaccine into the routine immunisation schedule accompanied by further catch-up campaigns.

Conclusions

The impact of COVID-19-related disruption to vaccination programs varies between infections and countries. Planning and implementation of campaigns should consider country and infection-specific epidemiological factors and local immunity gaps worsened by the COVID-19 pandemic when prioritising vaccines and strategies for catch-up vaccination.

Funding

Bill and Melinda Gates Foundation and Gavi, the Vaccine Alliance.

Effects of Air Pollution and Other Environmental Exposures on Estimates of Severe Influenza Illness, Washington, USA

Ecologic models of influenza burden may be confounded by other exposures that share winter seasonality. We evaluated the effects of air pollution and other environmental exposures in ecologic models estimating influenza-associated hospitalizations. We linked hospitalization data, viral surveillance, and environmental data, including temperature, relative humidity, dew point, and fine particulate matter for 3 counties in Washington, USA, for 2001-2012. We used negative binomial regression models to estimate the incidence of influenza-associated respiratory and circulatory (RC) hospitalizations and to assess the effect of adjusting for environmental exposures on RC hospitalization estimates. The modeled overall incidence rate of influenza-associated RC hospitalizations was 31/100,000 person-years. The environmental parameters were statistically associated with RC hospitalizations but did not appreciably affect the event rate estimates. Modeled influenza-associated RC hospitalization rates were similar to published estimates, and inclusion of environmental covariates in the model did not have a clinically important effect on severe influenza estimates.

Seroprevalence of SARS-CoV-2 antibodies in Seattle, Washington: October 2019-April 2020

BACKGROUND

The first US case of SARS-CoV-2 infection was detected on January 20, 2020. However, some serology studies suggest SARS-CoV-2 may have been present in the United States prior to that, as early as December 2019. The extent of domestic COVID-19 detection prior to 2020 has not been well-characterized.

OBJECTIVES

To estimate the prevalence of SARS-CoV-2 antibody among healthcare users in the greater Seattle, Washington area from October 2019 through early April 2020.

STUDY DESIGN

We tested residual samples from 766 Seattle-area adults for SARS-CoV-2 antibodies utilizing an ELISA against prefusion-stabilized Spike (S) protein.

RESULTS

No antibody-positive samples were found between October 2, 2019 and March 13, 2020. Prevalence rose to 1.2% in late March and early April 2020.

CONCLUSIONS

The absence of SARS-CoV-2 antibody-positive samples in October 2019 through mid-March, 2020, provides evidence against widespread circulation of COVID-19 among healthcare users in the Seattle area during that time. A small proportion of this metropolitan-area cohort had been infected with SARS-CoV-2 by spring of 2020.

A remote household-based approach to influenza self-testing and antiviral treatment

Background

Households represent important settings for transmission of influenza and other respiratory viruses. Current influenza diagnosis and treatment relies upon patient visits to healthcare facilities, which may lead to under‐diagnosis and treatment delays. This study aimed to assess the feasibility of an at‐home approach to influenza diagnosis and treatment via home testing, telehealth care, and rapid antiviral home delivery.

Methods

We conducted a pilot interventional study of remote influenza diagnosis and treatment in Seattle‐area households with children during the 2019‐2020 influenza season using pre‐positioned nasal swabs and home influenza tests. Home monitoring for respiratory symptoms occurred weekly; if symptoms were reported within 48 hours of onset, participants collected mid‐nasal swabs and used a rapid home‐based influenza immunoassay. An additional home‐collected swab was returned to a laboratory for confirmatory influenza RT‐PCR testing. Baloxavir antiviral treatment was prescribed and delivered to symptomatic and age‐eligible participants, following a telehealth encounter.

Results

124 households comprising 481 individuals self‐monitored for respiratory symptoms, with 58 home tests administered. 12 home tests were positive for influenza, of which eight were true positives confirmed by RT‐PCR. The sensitivity and specificity of the home influenza test were 72.7% and 96.2%, respectively. There were eight home deliveries of baloxavir, with 7 (87.5%) occurring within 3 hours of prescription and all within 48 hours of symptom onset.

Conclusions

We demonstrate the feasibility of self‐testing combined with rapid home delivery of influenza antiviral treatment. This approach may be an important control strategy for influenza epidemics and pandemics.

Effectiveness of Trivalent and Quadrivalent Inactivated Vaccines Against Influenza B in the United States, 2011-2012 to 2016-2017

Background

Since 2013, quadrivalent influenza vaccines containing 2 B viruses gradually replaced trivalent vaccines in the United States. We compared the vaccine effectiveness of quadrivalent to trivalent inactivated vaccines (IIV4 to IIV3, respectively) against illness due to influenza B during the transition, when IIV4 use increased rapidly.

Methods

The US Influenza Vaccine Effectiveness (Flu VE) Network analyzed 25 019 of 42 600 outpatients aged ≥6 months who enrolled within 7 days of illness onset during 6 seasons from 2011–2012. Upper respiratory specimens were tested for the influenza virus type and B lineage. Using logistic regression, we estimated IIV4 or IIV3 effectiveness by comparing the odds of an influenza B infection overall and the odds of B lineage among vaccinated versus unvaccinated participants. Over 4 seasons from 2013–2014, we compared the relative odds of an influenza B infection among IIV4 versus IIV3 recipients.

Results

Trivalent vaccines included the predominantly circulating B lineage in 4 of 6 seasons. During 4 influenza seasons when both IIV4 and IIV3 were widely used, the overall effectiveness against any influenza B was 53% (95% confidence interval [CI], 45–59) for IIV4 versus 45% (95% CI, 34–54) for IIV3. IIV4 was more effective than IIV3 against the B lineage not included in IIV3, but comparative effectiveness against illnesses related to any influenza B favored neither vaccine valency.

Conclusions

The uptake of quadrivalent inactivated influenza vaccines was not associated with increased protection against any influenza B illness, despite the higher effectiveness of quadrivalent vaccines against the added B virus lineage. Public health impact and cost-benefit analyses are needed globally.

Reducing Antibiotic Use in Ambulatory Care Through Influenza Vaccination

BACKGROUND

Improving appropriate antibiotic use is crucial for combating antibiotic resistance and unnecessary adverse drug reactions. Acute respiratory illness (ARI) commonly causes outpatient visits and accounts for ~41% of antibiotics used in the United States. We examined the influence of influenza vaccination on reducing antibiotic prescriptions among outpatients with ARI.

METHODS

We enrolled outpatients aged ≥6 months with ARI from 50-60 US clinics during 5 winters (2013-2018) and tested for influenza with RT-PCR; results were unavailable for clinical decision making and clinical influenza testing was infrequent. We collected antibiotic prescriptions and diagnosis codes for ARI syndromes. We calculated vaccine effectiveness (VE) by comparing vaccination odds among influenza-positive cases with test-negative controls. We estimated ARI visits and antibiotic prescriptions averted by influenza vaccination using estimates of VE, coverage, and prevalence of antibiotic prescriptions and influenza.

RESULTS

Among 37 487 ARI outpatients, 9659 (26%) were influenza positive. Overall, 36% of ARI and 26% of influenza-positive patients were prescribed antibiotics. The top 3 prevalent ARI syndromes included: viral upper respiratory tract infection (47%), pharyngitis (18%), and allergy or asthma (11%). Among patients testing positive for influenza, 77% did not receive an ICD-CM diagnostic code for influenza. Overall, VE against influenza-associated ARI was 35% (95% CI, 32-39%). Vaccination prevented 5.6% of all ARI syndromes, ranging from 2.8% (sinusitis) to 11% (clinical influenza). Influenza vaccination averted 1 in 25 (3.8%; 95% CI, 3.6-4.1%) antibiotic prescriptions among ARI outpatients during influenza seasons.

CONCLUSIONS

Vaccination and accurate influenza diagnosis may curb unnecessary antibiotic use and reduce the global threat of antibiotic resistance.

New insights into the cognitive effects of sleep deprivation by decomposition of a cognitive throughput task

STUDY OBJECTIVES

A cognitive throughput task known as the Digit Symbol Substitution Test (DSST) (or Symbol Digit Modalities Test) has been used as an assay of general cognitive slowing during sleep deprivation. Here, the effects of total sleep deprivation (TSD) on specific cognitive processes involved in DSST performance, including visual search, spatial memory, paired-associate learning, and motor response, were investigated through targeted task manipulations.

METHODS

A total of 12 DSST variants, designed to manipulate the use of specific cognitive processes, were implemented in two laboratory-based TSD studies with N = 59 and N = 26 subjects, respectively. In each study, the Psychomotor Vigilance Test (PVT) was administered alongside the DSST variants.

RESULTS

TSD reduced cognitive throughput on all DSST variants, with response time distributions exhibiting rightward skewing. All DSST variants showed practice effects, which were however minimized by inclusion of a pause between trials. Importantly, TSD-induced impairment on the DSST variants was not uniform, with a principal component analysis revealing three factors. Diffusion model decomposition of cognitive processes revealed that inter-individual differences during TSD on a two-alternative forced choice DSST variant were different from those on the PVT.

CONCLUSIONS

While reduced cognitive throughput has been interpreted to reflect general cognitive slowing, such TSD-induced impairment appears to reflect cognitive instability, like on the PVT, rather than general slowing. Further, comparisons between task variants revealed not one, but three distinct underlying processes impacted by sleep deprivation. Moreover, the practice effect on the task was found to be independent of the TSD effect and minimized by a task pacing manipulation.

Effects of weather-related social distancing on city-scale transmission of respiratory viruses: a retrospective cohort study

Background

Unusually high snowfall in western Washington State in February 2019 led to widespread school and workplace closures. We assessed the impact of social distancing caused by this extreme weather event on the transmission of respiratory viruses.

Methods

Residual specimens from patients evaluated for acute respiratory illness at hospitals in the Seattle metropolitan area were screened for a panel of respiratory viruses. Transmission models were fit to each virus to estimate the magnitude reduction in transmission due to weather-related disruptions. Changes in contact rates and care-seeking were informed by data on local traffic volumes and hospital visits.

Results

Disruption in contact patterns reduced effective contact rates during the intervention period by 16 to 95%, and cumulative disease incidence through the remainder of the season by 3 to 9%. Incidence reductions were greatest for viruses that were peaking when the disruption occurred and least for viruses in an early epidemic phase.

Conclusion

High-intensity, short-duration social distancing measures may substantially reduce total incidence in a respiratory virus epidemic if implemented near the epidemic peak. For SARS-CoV-2, this suggests that, even when SARS-CoV-2 spread is out of control, implementing short-term disruptions can prevent COVID-19 deaths.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06028-4.

Differences between Frequentist and Bayesian inference in routine surveillance for influenza vaccine effectiveness: a test-negative case-control study

Background

Routine influenza vaccine effectiveness (VE) surveillance networks use frequentist methods to estimate VE. With data from more than a decade of VE surveillance from diverse global populations now available, using Bayesian methods to explicitly account for this knowledge may be beneficial. This study explores differences between Bayesian vs. frequentist inference in multiple seasons with varying VE.

Methods

We used data from the United States Influenza Vaccine Effectiveness (US Flu VE) Network. Ambulatory care patients with acute respiratory illness were enrolled during seasons of varying observed VE based on traditional frequentist methods. We estimated VE against A(H1N1)pdm in 2015/16, dominated by A(H1N1)pdm; against A(H3N2) in 2017/18, dominated by A(H3N2); and compared VE for live attenuated influenza vaccine (LAIV) vs. inactivated influenza vaccine (IIV) among children aged 2–17 years in 2013/14, also dominated by A(H1N1)pdm. VE was estimated using both frequentist and Bayesian methods using the test-negative design. For the Bayesian estimates, prior VE distributions were based on data from all published test-negative studies of the same influenza type/subtype available prior to the season of interest.

Results

Across the three seasons, 16,342 subjects were included in the analyses. For 2015/16, frequentist and Bayesian VE estimates were essentially identical (41% each). For 2017/18, frequentist and Bayesian estimates of VE against A(H3N2) viruses were also nearly identical (26% vs. 23%, respectively), even though the presence of apparent antigenic match could potentially have pulled Bayesian estimates upward. Precision of estimates was similar between methods in both seasons. Frequentist and Bayesian estimates diverged for children in 2013/14. Under the frequentist approach, LAIV effectiveness was 62 percentage points lower than IIV, while LAIV was only 27 percentage points lower than IIV under the Bayesian approach.

Conclusion

Bayesian estimates of influenza VE can differ from frequentist estimates to a clinically meaningful degree when VE diverges substantially from previous seasons.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-10543-z.

Paid Leave and Access to Telework as Work Attendance Determinants during Acute Respiratory Illness, United States, 2017-2018

We assessed determinants of work attendance during the first 3 days after onset of acute respiratory illness (ARI) among workers 19-64 years of age who had medically attended ARI or influenza during the 2017-2018 influenza season. The total number of days worked included days worked at the usual workplace and days teleworked. Access to paid leave was associated with fewer days worked overall and at the usual workplace during illness. Participants who indicated that employees were discouraged from coming to work with influenza-like symptoms were less likely to attend their usual workplace. Compared with workers without a telework option, those with telework access worked more days during illness overall, but there was no difference in days worked at the usual workplace. Both paid leave benefits and business practices that actively encourage employees to stay home while sick are necessary to reduce the transmission of ARI and influenza in workplaces.

Influenza vaccination coverage among persons seeking outpatient medical care for acute respiratory illness in five states in the United States, 2011-2012 through 2018-2019

BACKGROUND

In the United States (U.S.), annual influenza vaccination has been recommended for all persons aged ≥6 months with the Healthy People 2020 coverage target of 70%. However, vaccination coverage has remained around 42-49% during the past eight influenza seasons. We sought to quantify influenza vaccination coverage and factors associated with vaccination in persons seeking outpatient medical care for an acute respiratory illness (ARI).

METHODS

We enrolled outpatients aged ≥6 months with ARI from >50 U.S. clinics from 2011 to 2012 through 2018-2019 influenza seasons and tested for influenza with molecular assays. Vaccination status was based on documented receipt of the current season's influenza vaccine. We estimated vaccination coverage among influenza-negative study participants by study site, age, and season, and compared to state-level influenza coverage estimates in the general population based on annual immunization surveys. We used multivariable logistic regression to examine factors independently associated with receipt of influenza vaccines.

RESULTS

We enrolled 45,424 study participants with ARI who tested negative for influenza during the study period. Annual vaccination coverage among influenza-negative ARI patients and the general population in the participating states averaged 55% (range: 47-62%), and 52% (range: 46-54%), respectively. Among enrollees, coverage was highest among adults aged ≥65 years (82%; range, 80-85%) and lowest among adolescents aged 13-17 years (38%; range, 35-41%). Factors significantly associated with non-vaccination included non-White race, no college degree, exposure to cigarette smoke, absence of high-risk conditions, and not receiving prior season influenza vaccine.

CONCLUSIONS

Influenza vaccination coverage over eight seasons among outpatients with non-influenza respiratory illness was slightly higher than coverage in the general population but 15% lower than national targets. Increased efforts to promote vaccination especially in groups with lower coverage are warranted to attain optimal health benefits of influenza vaccine.

Estimating the health impact of vaccination against ten pathogens in 98 low-income and middle-income countries from 2000 to 2030: a modelling study

BACKGROUND

The past two decades have seen expansion of childhood vaccination programmes in low-income and middle-income countries (LMICs). We quantify the health impact of these programmes by estimating the deaths and disability-adjusted life-years (DALYs) averted by vaccination against ten pathogens in 98 LMICs between 2000 and 2030.

METHODS

16 independent research groups provided model-based disease burden estimates under a range of vaccination coverage scenarios for ten pathogens: hepatitis B virus, Haemophilus influenzae type B, human papillomavirus, Japanese encephalitis, measles, Neisseria meningitidis serogroup A, Streptococcus pneumoniae, rotavirus, rubella, and yellow fever. Using standardised demographic data and vaccine coverage, the impact of vaccination programmes was determined by comparing model estimates from a no-vaccination counterfactual scenario with those from a reported and projected vaccination scenario. We present deaths and DALYs averted between 2000 and 2030 by calendar year and by annual birth cohort.

FINDINGS

We estimate that vaccination of the ten selected pathogens will have averted 69 million (95% credible interval 52-88) deaths between 2000 and 2030, of which 37 million (30-48) were averted between 2000 and 2019. From 2000 to 2019, this represents a 45% (36-58) reduction in deaths compared with the counterfactual scenario of no vaccination. Most of this impact is concentrated in a reduction in mortality among children younger than 5 years (57% reduction [52-66]), most notably from measles. Over the lifetime of birth cohorts born between 2000 and 2030, we predict that 120 million (93-150) deaths will be averted by vaccination, of which 58 million (39-76) are due to measles vaccination and 38 million (25-52) are due to hepatitis B vaccination. We estimate that increases in vaccine coverage and introductions of additional vaccines will result in a 72% (59-81) reduction in lifetime mortality in the 2019 birth cohort.

INTERPRETATION

Increases in vaccine coverage and the introduction of new vaccines into LMICs have had a major impact in reducing mortality. These public health gains are predicted to increase in coming decades if progress in increasing coverage is sustained.

FUNDING

Gavi, the Vaccine Alliance and the Bill & Melinda Gates Foundation.

Epidemiology of Respiratory Syncytial Virus Across Five Influenza Seasons Among Adults and Children One Year of Age and Older-Washington State, 2011/2012-2015/2016

BACKGROUND

Vaccines and novel prophylactics against respiratory syncytial virus (RSV) are in development. To provide a baseline for evaluating these interventions, we characterized the incidence and molecular epidemiology of RSV in persons aged ≥1 year.

METHODS

We identified patients with medically attended acute respiratory illness (MAARI) from the 2011/2012 through 2015/2016 influenza seasons among members of Kaiser Permanente Washington. We estimated the cumulative incidence of MAARI for laboratory-confirmed RSV or influenza infection.

RESULTS

Annual cohorts ranged from 82 266 to 162 633 individuals, 14% of whom were children aged 1 to 17 years. Cumulative incidence of RSV each season ranged from 14 per 1000 population (95% confidence interval [CI], 12-16) to 22 per 1000 (95% CI, 19-25). Incidence of RSV was greater than influenza in children aged 12-23 months and 2-4 years; incidence of influenza was greater in other age groups. Respiratory syncytial virus subtype A dominated in 2011/2012, 2012/2013, and 2015/2016, with ON1 being the most common genotype. Respiratory syncytial virus subtype B dominated in 2013/2014 and 2014/2015, primarily of the BA genotype.

CONCLUSIONS

The burden of RSV is comparable to that of influenza across the life course. These results provide a baseline for evaluating the impact of new RSV interventions on the epidemiology of RSV.

Characteristics of COVID-19 in Homeless Shelters : A Community-Based Surveillance Study

BACKGROUND

Homeless shelters are a high-risk setting for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission because of crowding and shared hygiene facilities.

OBJECTIVE

To investigate SARS-CoV-2 case counts across several adult and family homeless shelters in a major metropolitan area.

DESIGN

Cross-sectional, community-based surveillance study. (ClinicalTrials.gov: NCT04141917).

SETTING

14 homeless shelters in King County, Washington.

PARTICIPANTS

A total of 1434 study encounters were done in shelter residents and staff, regardless of symptoms.

INTERVENTION

2 strategies were used for SARS-CoV-2 testing: routine surveillance and contact tracing ("surge testing") events.

MEASUREMENTS

The primary outcome measure was test positivity rate of SARS-CoV-2 infection at shelters, determined by dividing the number of positive cases by the total number of participant encounters, regardless of symptoms. Sociodemographic, clinical, and virologic variables were assessed as correlates of viral positivity.

RESULTS

Among 1434 encounters, 29 (2% [95% CI, 1.4% to 2.9%]) cases of SARS-CoV-2 infection were detected across 5 shelters. Most (n = 21 [72.4%]) were detected during surge testing events rather than routine surveillance, and most (n = 21 [72.4% {CI, 52.8% to 87.3%}]) were asymptomatic at the time of sample collection. Persons who were positive for SARS-CoV-2 were more frequently aged 60 years or older than those without SARS-CoV-2 (44.8% vs. 15.9%). Eighty-six percent of persons with positive test results slept in a communal space rather than in a private or shared room.

LIMITATION

Selection bias due to voluntary participation and a relatively small case count.

CONCLUSION

Active surveillance and surge testing were used to detect multiple cases of asymptomatic and symptomatic SARS-CoV-2 infection in homeless shelters. The findings suggest an unmet need for routine viral testing outside of clinical settings for homeless populations.

PRIMARY FUNDING SOURCE

Gates Ventures.

Clinical Symptoms Among Ambulatory Patients Tested for SARS-CoV-2

We compared symptoms and characteristics of 4961 ambulatory patients with and without laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection. Findings indicate that clinical symptoms alone would be insufficient to distinguish between coronavirus disease 2019 and other respiratory infections (eg, influenza) and/or to evaluate the effects of preventive interventions (eg, vaccinations).

Point-of-care molecular testing and antiviral treatment of influenza in residents of homeless shelters in Seattle, WA: study protocol for a stepped-wedge cluster-randomized controlled trial

Introduction

Influenza is an important public health problem, but data on the impact of influenza among homeless shelter residents are limited. The primary aim of this study is to evaluate whether on-site testing and antiviral treatment of influenza in residents of homeless shelters reduces influenza spread in these settings.

Methods and analysis

This study is a stepped-wedge cluster-randomized trial of on-site testing and antiviral treatment for influenza in nine homeless shelter sites within the Seattle metropolitan area. Participants with acute respiratory illness (ARI), defined as two or more respiratory symptoms or new or worsening cough with onset in the prior 7 days, are eligible to enroll. Approximately 3200 individuals are estimated to participate from October to May across two influenza seasons. All sites will start enrollment in the control arm at the beginning of each season, with routine surveillance for ARI. Sites will be randomized at different timepoints to enter the intervention arm, with implementation of a test-and-treat strategy for individuals with two or fewer days of symptoms. Eligible individuals will be tested on-site with a point-of-care influenza test. If the influenza test is positive and symptom onset is within 48 h, participants will be administered antiviral treatment with baloxavir or oseltamivir depending upon age and comorbidities. Participants will complete a questionnaire on demographics and symptom duration and severity. The primary endpoint is the incidence of influenza in the intervention period compared to the control period, after adjusting for time trends.

Trial registration

ClinicalTrials.gov NCT04141917. Registered 28 October 2019. Trial sponsor: University of Washington.

Supplementary information

The online version contains supplementary material available at 10.1186/s13063-020-04871-5.

Relative effectiveness of high dose versus standard dose influenza vaccines in older adult outpatients over four seasons, 2015-16 to 2018-19

BACKGROUND

New influenza vaccine formulations are designed to improve vaccine effectiveness and protect those most vulnerable to infection. High dose trivalent inactivated influenza vaccine (HD-IIV3), licensed for ages ≥65 years, produces greater antibody responses and efficacy in clinical trials, but post-licensure vaccine effectiveness (VE) compared to standard dose (SD-IIV3/4) vaccine remains an open question.

METHODS

Using a test-negative, case control design and propensity analyses to adjust for confounding, US Influenza VE Network data from the 2015-2016 through 2018-2019 seasons were analyzed to determine relative VE (rVE) between HD-IIV3 and SD-IIV3/4 among outpatients ≥65 years old presenting with acute respiratory illness. Influenza vaccination status was derived from electronic medical records and immunization registries.

RESULTS

Among 3861 enrollees, 2993 (78%) were vaccinated; 1573 (53%) received HD-IIV3 and 1420 (47%) received SD-IIV3/4. HD-IIV3 recipients differed from SD-IIV3/4 recipients by race, previous vaccination, number of outpatient visits in the previous year and timing of vaccination, and were balanced in the propensity model except the timing of vaccination. Compared with no vaccination, significant protection against any influenza A was observed from both HD-IIV3 (VE = 29%; 95%CI = 10%, 44%) and SD-IIV3/4 (VE = 24%; 95%CI = 5%, 39%); rVE = 18% (95%CI = 0%, 33%, SD as referent). When stratified by virus type, against A/H1N1, HD-IIV3 VE was 30% (95%CI = -7%, 54%), SD-IIV3/4 VE was 40% (95%CI = 10%, 61%), and rVE = -32%; (95%CI = -94%, 11%); Against A/H3N2, HD-IIV3 VE was 31% (95%CI = 9%, 47%), SD-IIV3/4 VE was 19% (95%CI = -5%, 37%), and rVE = 27%; (95% CI = 9%, 42%).

CONCLUSIONS

Among adults ≥65 years of age, recipients of standard and high dose influenza vaccines differed significantly in their characteristics. After adjusting for these differences, high dose vaccine offered more protection against A/H3N2 and borderline significant protection against all influenza A requiring outpatient care during the 2015-2018 influenza seasons.

Low-impact social distancing interventions to mitigate local epidemics of SARS-CoV-2

Many jurisdictions implemented intensive social distancing to suppress SARS-CoV-2 transmission. The challenge now is to mitigate the ongoing COVID-19 epidemic without overburdening economic and social activities. An agent-based model simulated the population of King County, Washington. SARS-CoV-2 transmission probabilities were estimated by fitting simulated to observed hospital admissions. Interventions considered included encouraging telecommuting, reducing contacts to high-risk persons, and reductions to contacts outside of the home, among others. Removing all existing interventions would result in nearly 42,000 COVID-19 hospitalizations between June 2020 and January 2021, with peak hospital occupancy exceeding available beds 6-fold. Combining interventions is predicted to reduce total hospitalizations by 48% (95% CI, 47-49%), with peak COVID-19 hospital occupancy of 70% of total beds. Targeted school closures can further reduce the peak occupancy. Combining low-impact interventions may mitigate the course of the COVID-19 epidemic, keeping hospital burden within the capacity of the healthcare system.

Influenza Vaccine Effectiveness in the United States During the 2016-2017 Season

BACKGROUND

In recent influenza seasons, the effectiveness of inactivated influenza vaccines against circulating A(H3N2) virus has been lower than against A(H1N1)pdm09 and B viruses, even when circulating viruses remained antigenically similar to vaccine components.

METHODS

During the 2016-2017 influenza season, vaccine effectiveness (VE) across age groups and vaccine types was examined among outpatients with acute respiratory illness at 5 US sites using a test-negative design that compared the odds of vaccination among reverse transcription polymerase chain reaction-confirmed influenza positives and negatives.

RESULTS

Among 7083 enrollees, 1342 (19%) tested positive for influenza A(H3N2), 648 (9%) were positive for influenza B (including B/Yamagata, n = 577), and 5040 (71%) were influenza negative. Vaccine effectiveness was 40% (95% confidence interval [CI], 32% to 46%) against any influenza virus, 33% (95% CI, 23% to 41%) against influenza A(H3N2) viruses, and 53% (95% CI, 43% to 61%) against influenza B viruses.

CONCLUSIONS

The 2016-2017 influenza vaccines provided moderate protection against any influenza among outpatients but were less protective against influenza A(H3N2) viruses than B viruses. Approaches to improving effectiveness against A(H3N2) viruses are needed.

Influenza Vaccine Effectiveness and Statin Use Among Adults in the United States, 2011-2017

BACKGROUND

Statin medications have immunomodulatory effects. Several recent studies suggest that statins may reduce influenza vaccine response and reduce influenza vaccine effectiveness (VE).

METHODS

We compared influenza VE in statin users and nonusers aged ≥45 years enrolled in the US Vaccine Effectiveness Network study over 6 influenza seasons (2011-2012 through 2016-2017). All enrollees presented to outpatients clinics with acute respiratory illness and were tested for influenza. Information on vaccination status, medical history, and statin use at the time of vaccination were collected by medical and pharmacy records. Using a test-negative design, we estimated VE as (1 - OR) × 100, in which OR is the odds ratio for testing positive for influenza virus among vaccinated vs unvaccinated participants.

RESULTS

Among 11692 eligible participants, 3359 (30%) were statin users and 2806 (24%) tested positive for influenza virus infection; 78% of statin users and 60% of nonusers had received influenza vaccine. After adjusting for potential confounders, influenza VE was 36% (95% confidence interval [CI], 22%-47%) among statin users and 39% (95% CI, 32%-45%) among nonusers. We observed no significant modification of VE by statin use. VE against influenza A(H1N1)pdm09, A(H3N2), and B viruses were similar among statin users and nonusers.

CONCLUSIONS

In this large observational study, influenza VE against laboratory-confirmed influenza illness was not affected by current statin use among persons aged ≥45 years. Statin use did not modify the effect of vaccination on influenza when analyzed by type and subtype.

Influenza Vaccine Effectiveness in Preventing Influenza-associated Hospitalizations During Pregnancy: A Multi-country Retrospective Test Negative Design Study, 2010-2016

BACKGROUND

To date, no study has examined influenza vaccine effectiveness (IVE) against laboratory-confirmed influenza-associated hospitalizations during pregnancy.

METHODS

The Pregnancy Influenza Vaccine Effectiveness Network (PREVENT) consisted of public health or healthcare systems with integrated laboratory, medical, and vaccination records in Australia, Canada (Alberta and Ontario), Israel, and the United States (California, Oregon, and Washington). Sites identified pregnant women aged 18 through 50 years whose pregnancies overlapped with local influenza seasons from 2010 through 2016. Administrative data were used to identify hospitalizations with acute respiratory or febrile illness (ARFI) and clinician-ordered real-time reverse transcription polymerase chain reaction (rRT-PCR) testing for influenza viruses. Overall IVE was estimated using the test-negative design and adjusting for site, season, season timing, and high-risk medical conditions.

RESULTS

Among 19450 hospitalizations with an ARFI discharge diagnosis (across 25 site-specific study seasons), only 1030 (6%) of the pregnant women were tested for influenza viruses by rRT-PCR. Approximately half of these women had pneumonia or influenza discharge diagnoses (54%). Influenza A or B virus infections were detected in 598/1030 (58%) of the ARFI hospitalizations with influenza testing. Across sites and seasons, 13% of rRT-PCR-confirmed influenza-positive pregnant women were vaccinated compared with 22% of influenza-negative pregnant women; the adjusted overall IVE was 40% (95% confidence interval = 12%-59%) against influenza-associated hospitalization during pregnancy.

CONCLUSION

Between 2010 and 2016, influenza vaccines offered moderate protection against laboratory-confirmed influenza-associated hospitalizations during pregnancy, which may further inform the benefits of maternal influenza vaccination programs.

Patterns of Influenza Vaccination and Vaccine Effectiveness Among Young US Children Who Receive Outpatient Care for Acute Respiratory Tract Illness

IMPORTANCE

The burden of influenza among young children is high, and influenza vaccination is the primary strategy to prevent the virus and its complications. Less is known about differences in clinical protection following 1 vs 2 doses of initial influenza vaccination.

OBJECTIVES

To describe patterns of influenza vaccination among young children who receive outpatient care for acute respiratory tract illness in the US and compare vaccine effectiveness (VE) against medically attended laboratory-confirmed influenza by number of influenza vaccine doses received.

DESIGN

This test-negative case-control study was conducted in outpatient clinics, including emergency departments, at 5 sites of the US Influenza Vaccine Effectiveness Network during the 2014-2015 through 2017-2018 influenza seasons. The present study was performed from November 5, 2014, to April 12, 2018, during periods of local influenza circulation. Children aged 6 months to 8 years with an acute respiratory tract illness with cough who presented for outpatient care within 7 days of illness onset were included. All children were tested using real-time, reverse-transcriptase polymerase chain reaction for influenza for research purposes.

EXPOSURES

Vaccination in the enrollment season with either 1 or 2 doses of inactivated influenza vaccine as documented from electronic medical records, including state immunization information systems.

MAIN OUTCOMES AND MEASURES

Medically attended acute respiratory tract infection with real-time, reverse-transcriptase polymerase chain reaction testing for influenza.

RESULTS

Of 7533 children, 3480 children (46%) were girls, 4687 children (62%) were non-Hispanic white, and 4871 children (65%) were younger than 5 years. A total of 3912 children (52%) were unvaccinated in the enrollment season, 2924 children (39%) were fully vaccinated, and 697 children (9%) were partially vaccinated. Adjusted VE against any influenza was 51% (95% CI, 44%-57%) among fully vaccinated children and 41% (95% CI, 25%-54%) among partially vaccinated children. Among 1519 vaccine-naive children aged 6 months to 2 years, the VE of 2 doses in the enrollment season was 53% (95% CI, 28%-70%), and the VE of 1 dose was 23% (95% CI, -11% to 47%); those who received 2 doses were less likely to test positive for influenza compared with children who received only 1 dose (adjusted odds ratio, 0.57; 95% CI, 0.35-0.93).

CONCLUSIONS AND RELEVANCE

Consistent with US influenza vaccine policy, receipt of the recommended number of doses resulted in higher VE than partial vaccination in 4 influenza seasons. Efforts to improve 2-dose coverage for previously unvaccinated children may reduce the burden of influenza in this population.