A new study from Canadian researchers shows the Modified Vaccinia Ankara – Bavarian Nordic vaccine (MVA-BN), a smallpox vaccine that provides protection against other orthopoxviruses, was safe when used among people in Toronto and Vancouver at high risk for contracting mpox.

The study was published yesterday in Vaccine.

In June of 2022 amidst a global mpox outbreak, Canada launched a publicly funded vaccination campaign to offer MVA-BN to at-risk populations, including men who have sex with men and sex workers. Adverse and safety outcomes were monitored in this prospective study among participants who received a survey 7 and 30 days after each MVA-BN dose.

No myocarditis recorded

In total, 1,173 vaccinated participants completed a 7-day survey, and 75% of those participants also completed a 30-day survey. The surveys were completed from September 15, 2022, through April 14, 2023.

The most common adverse event was mild to moderate injection-site pain, which was reported by 60% of vaccinated participants. No hospitalizations were reported among vaccine recipients, but 40 participants (3.4%) said adverse events following vaccination limited their ability to participate in work or school.

No cases of severe neurological disease, skin disease, or myocarditis were identified.

"No cases of severe neurological disease, skin disease, or myocarditis were identified," the authors wrote. "MVA-BN was well tolerated overall, with few reported symptoms of sufficient severity to interfere with daily activities or require medical assessment."

The study adds to a growing body of literature that suggests second-generation smallpox vaccines are safe and rarely cause significant side effects.

The findings from a randomized clinical trial in Spain support de-escalation of antibiotic therapy in patients with bacteremia caused by Enterobacterales, researchers reported yesterday in The Lancet Infectious Diseases.

Although empiric treatment with antipseudomonal beta-lactams is often necessary with severe infections to ensure that the causative organism is covered, these drugs can exert selection pressure for resistance mechanisms and increase the risk of Clostridioides difficile, which is why de-escalation to a narrower-spectrum drug is recommended once the infecting pathogen has been identified. But the dearth of evidence on the safety and efficacy of de-escalation in specific clinical situations has been a barrier to wider acceptance of the practice.

To determine the safety and efficacy of de-escalation in patients with bacteremia caused by Enterobacterales, investigators randomly assigned trial participants to de-escalate to one of several antibiotics according to susceptibility (the de-escalation group) in the first 48 hours after the antimicrobial susceptibility report was available or to continue with empiric treatment (the control group). The primary outcome was clinical cure 3 to 5 days after end of treatment. The non-inferiority margin was –10%.

Potential ecological benefit

Of the 344 patients assigned to the treatment groups, 164 patients in the de-escalation group and 173 in the control group were included in the modified intention-to-treat (mITT) population. Analysis of the primary outcome showed that 90% of patients in the de-escalation group had clinical cure, compared with 89% in the control group, for a risk difference of 1.6 percentage points (95% confidence interval, –5.0 to 8.2).

Given the potential ecological benefit, these results provide evidence to implement active actions to promote de-escalation in this clinical setting.

The number of adverse events reported was 219 in the de-escalation group and 175 in the control group, with 24% and 32% considered severe, respectively. Five percent of patients in the de-escalation group and 6% in the control group died during the 60-day follow-up, but no deaths were treatment-related.

The investigators note that the most frequent sources of bacteremia were the urinary and biliary tracts, so the results apply mainly to those populations.

"Given the potential ecological benefit, these results provide evidence to implement active actions to promote de-escalation in this clinical setting," they wrote.

Chronic wasting disease (CWD) has been detected in another Wyoming elk hunt area, according to the Wyoming Game and Fish Department (WGFD).

In a news release yesterday, WGFD said the fatal neurodegenerative infection was confirmed in a hunter-harvested cow elk in Elk Hunt Area 28 in late December. The hunt area is in the Lander area in the central part of the state and borders Elk Hunt areas 98 and 127, where CWD was confirmed in 2021 and 2022, respectively.

In 2022, WGFD tested 6,701 lymph node samples from deer, elk, and moose, most of them hunter-submitted.

Caused by misfolded proteins called prions, CWD isn't known to infect humans or other non-cervid animals, but experts worry it could jump species. The Centers for Disease Control and Prevention recommends against consuming meat from obviously ill animals or those that test positive for CWD.

With the start of 2024, highly pathogenic avian flu outbreaks have already been confirmed in four states, with California the hardest-hit state, according to the latest updates from the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS).

In California, the virus was detected at three more commercial farms, including a layer pullet farm in Merced County housing more than 760,000 birds, a broiler farm in Merced County that has nearly 535,000 birds, and a broiler farm in Sonoma County that has nearly 78,000 birds. Also, officials reported an outbreak involving two of the state's backyard flocks, one in Merced County and the other in Sacramento County.

Meanwhile, two other states reported outbreaks affecting commercial farms. Wisconsin reported an event at a turkey facility in Washburn County that has 41,000 birds, and in Kansas, the virus hit a layer pullet farm in Rice County that was raising 240,000 birds. Colorado reported an outbreak in a backyard flock in Arapahoe County.

So far this year avian flu outbreaks have led to the loss of 1.66 million birds, APHIS said. The H5N1 outbreaks began in US poultry in February 2022 and have so far led to a record loss of 81.37 million birds across 47 states.