News Scan for Apr 07, 2020

Protection with cell-culture flu vaccine
Violence in Ebola outbreak
Yellow fever in Ethiopia

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 (Rt) of 1.06. When violent attacks, especially those aimed at civilians took place, the Rt 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 Rt 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

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