News Scan for Apr 07, 2020

News brief

Study reports superior efficacy of cell-cultured 4-strain flu vaccine

Seqirus's cell-cultured quadrivalent (four-strain) seasonal flu vaccine was about 36% more effective than a standard egg-derived equivalent during the 2017-18 US flu season, according to findings from a large study published today in Clinical Infectious Diseases.

Because flu viral antigens can mutate during chicken egg-based vaccine production and impair their effectiveness, Seqirus's 2017-18 Flucelvax vaccine was made using an A(H3N2) seed virus propagated only in canine kidney-based cell culture.

The first such flu vaccine approved for use in the United States and Europe, Flucelvax contained three other flu strains made from egg isolates that season. H3N2, which is typically associated with more severe disease, was the predominant circulating strain that year.

In the retrospective cohort study, the researchers, half of whom work for Seqirus, analyzed flu vaccination, outcome, and covariate data from the electronic medical records of 1,353,862 patients 4 years old or older at primary care facilities enrolled in the Allscripts Health Insights research database from Aug 1, 2017, to Mar 30, 2018.

They estimated relative vaccine effectiveness (rVE) against flu-like illness using diagnostic ICD-9 and ICD-10 codes and estimated the adjusted odds ratios used to estimate rVE from multivariable logistic regression models adjusted for age, sex, race and ethnicity, geographic region, and health status.

Of the 92,187 patients who received Flucelvax, 1,705 (1.9%) had a narrowly defined flu-like illness, while 25,645 (2.1%) of the 1,261,675 patients who received egg-derived vaccine became ill. Crude rVE was 9.2% (4.6% to 13.6%). After adjusting for age, sex, health status, underlying illnesses, and geographic area, estimated rVE was 36.2% (26.1% to 44.9%).

"Using mammalian cells to propagate vaccine-strain influenza viruses reduces the chance of mutations that arise during the vaccine production process," the authors wrote. "As a result, cell-culture technology improves the match between the vaccine virus strain and vaccine selected strain."

Although flu vaccines include the strains expected to circulate each year, the effectiveness of egg-derived vaccines varies by season. The authors noted that findings from a retrospective analysis of flu seasons from 2002-03 through 2017-18 suggest that mutations that occurred during egg-based vaccine production lowered their effectiveness in a number of seasons.
Apr 7 Clin Infect Dis abstract

Study shows violent outbreaks tied to Ebola spread in DRC

A study today in The Journal of Infectious Diseases showed that violence in the eastern Democratic Republic of the Congo (DRC) during the current Ebola outbreak was associated with enhanced disease spread.

The outbreak began in August 2018 in North Kivu and Ituri provinces and has to date infected at least 3,453 people, including 2,273 deaths. Despite the use of two Ebola vaccines, the outbreak has proven difficult to end because of repeated violent attacks in the outbreak region which have halted surveillance response work for weeks at a time, but the country has now gone several weeks without an Ebola virus disease (EVD) case.

In the study, the authors show that the outbreak had an estimated daily reproduction number (R_t) of 1.06. When violent attacks, especially those aimed at civilians took place, the R_t jumped to 1.43 (95% confidence interval [CI], 1.21 to 1.35) in the 21 days afterward. When the attacks targeted Ebola response efforts, the R_t rose to 1.52 (95% CI, 1.30-1.74).

"The cumulative effect of violent events can have devastating consequences on transmission, as we observed when sixteen events over a 21-day interval increased EVD transmission by 60%," the authors said.
Apr 7 J Infect Dis study

Yellow fever outbreak in Ethiopia sickens 85

A yellow fever outbreak in Ethiopia's Gurage zone in the west central part of the country has sickened 85 people so far, 4 of them fatally, the World Health Organization (WHO) African regional office said in its latest weekly outbreaks and health emergencies report.

The outbreak began in early March with a family cluster involving three suspected cases, and samples from two of the patients were confirmed as positive. An investigation in the wake of the illnesses has identified 85 cases: 2 confirmed, 6 presumed positive, and 77 suspected. Tests are under way on samples from the suspected case-patients. Also, initial results reveal Aedes mosquitoes, a yellow fever vector, in the area around several households.

Authorities have launched a yellow fever vaccine campaign targeting 32,000 people in 12 affected neighborhoods, and health officials have asked the International Coordinating Group for enough vaccine to hold a mass vaccination campaign. Ethiopia has also applied for funding to introduce yellow fever vaccine into its routine immunization program.

Yellow fever is endemic in Ethiopia, and the country has had outbreaks before, most recently in 2018. Ethiopia is classified as a high-risk nation, and population immunity is estimated to be low in the outbreak area. The WHO said the early-March onset of the rainy season will probably increase the disease burden in the weeks ahead, raising the risk of the disease moving into more crowded urban areas.
Apr 6 WHO Africa regional office weekly report

Stewardship / Resistance Scan for Apr 07, 2020

News brief

Nursing home study finds mixed results for antibiotic time-outs

Despite an increase in the frequency of early discontinuation of broad-spectrum antibiotics, the use of an antibiotic time-out (ATO) in nursing homes in Wisconsin and Pennsylvania had mixed results overall, researchers reported today in Infection Control and Hospital Epidemiology.

To evaluate the impact of the ATO intervention, in which antibiotic prescriptions are assessed 48 to 72 hours after initiation, researchers from the University of Pittsburgh School of Medicine and the University of Wisconsin School of Medicine & Public Health collected data on 11 nursing homes over 25 months. They looked specifically at the effect of the intervention on the frequency and type of antibiotic change events (ACEs) and the extent to which initial antibiotic choice (broad- or narrow-spectrum) modified observed ACE patterns.

ACEs were categorized as early discontinuation, class modification, or administration modification. Analyses were performed using a difference-in-difference (DiD) approach.

Of 2,647 antibiotic events initiated in study nursing homes (1,498 in intervention facilities, 1,149 in control facilities, 376 (14.2%) were associated with an ACE. The overall proportion of ACEs did not significantly differ between intervention and control nursing homes. Early discontinuation ACEs increased in intervention nursing homes (DiD, 2.5%; P = .01), primarily affecting residents initiated on broad-spectrum antibiotics (DiD, 2.9%; P < .01). But the increase in early-discontinuation ACEs was offset by a reduction in class modification ACEs in intervention nursing homes.

The results are noteworthy because ATOs are one of the few antibiotic stewardship interventions that nursing homes can implement, yet few studies have looked at whether they have utility outside the hospital setting. The authors of the study say more research is needed.

"Although we did not observe the increase in ACEs in intervention nursing homes that we expected, we did find evidence that the ATO intervention did increase the frequency of early discontinuation ACEs," they write. "Consequently, we believe that our results justify further studies designed to isolate the effects of ATO interventions on the postprescriptive decision making by nursing home providers."
Apr 7 Infect Control Hosp Epidemiol abstract

Survey: High use of hospital antifungal stewardship strategies

In another study today in the same journal, the results of a survey show that use of antifungal stewardship strategies is high at hospitals within the Society for Healthcare Epidemiology of America's (SHEA) Research Network (SRN).

Of the 111 hospitals that received the survey, 45 (41%) responded, and 60% of those hospitals had large, well-established antibiotic stewardship programs (ASPs). In 43 hospitals, the ASPs used antifungal stewardship strategies, most commonly prospective audit and feedback (73.3%) led by a pharmacist, followed by prior authorization and restriction (67.4%). Roughly half of responding hospitals reported using education (47.0%) or creating guidelines for invasive fungal infection (IFI) management (51.1%).

Although the authors of the study hypothesized that larger and more well-established ASPs and hospitals caring for transplant patients would be more likely to use antifungal stewardship strategies, they found that there was a subset of respondents from private or community hospitals with small ASPs and no transplant populations, and they did not detect any significant associations among ASP size, ASP duration, presence of transplant populations, and higher likelihood of using antifungal stewardship strategies.

"In conclusion, we found that most hospital ASPs within the SRN have implemented antifungal stewardship strategies, including ASPs in smaller, nonacademic hospitals," the authors write. "Important areas for continued expansion of antifungal stewardship include education and institutional guideline development, implementation of rapid laboratory diagnostics, and surveillance of antifungal use with reporting to the NHSN [National Healthcare Safety Network]."
Apr 7 Infect Control Hosp Epidemiol abstract