An international study reveals that flu vaccines greatly reduce both pneumonia and cardiovascular complications in people with heart failure. The study was conducted by researchers from McMaster University in Canada and published in The Lancet Global Health.

The large randomized controlled trial was conducted in 10 countries in Asia, Africa, and the Middle East. Heart failure patients were matched 1:1 to receive either an annual flu shot for up to 3 years or a placebo injection of saline.

A total of 5,129 patients were involved in the study, which ran from 2015 to 2021. Over half of participants (51.4%) were women, and the mean age was 57.2 years. A total of 20.7% of participants had a previous myocardial infarction, and 8.0% had had a previous stroke.

Over the course of 1 year, a flu vaccine reduced pneumonia by 40% and hospitalization by 15% in patients with heart failure. During influenza season in the fall and winter, the vaccine reduced deaths by 20% in these patients.

Most important, fewer study participants had all-cause hospitalization in the vaccine group than in the placebo group (388 participants [15.2%] vs 455 participants [17.7%]; hazard ratio [HR], 0.84 [95% confidence interval [CI], 0.74 to 0.97]), and there were fewer recurrent all-cause hospitalizations in the vaccine group than in the placebo group (557 participants [21.8%] vs 671 participants [26.1%]; HR, 0.84 [95% CI, 0.75 to 0.94]).

'Underappreciated' effect

In a commentary on the study, authors write that an estimated 1 billion people get flu annually around the world, with 5 million of those cases severe. More than 1 in 5 patients with heart failure have a recurrent cardiovascular event during an influenza infection.

"It is underappreciated that influenza vaccine can save people from cardiovascular death," said first study author Mark Loeb, MD, in a press release.

According to a study published yesterday in Emerging Infectious Diseases from researchers at Yale University, exit COVID-19 rapid antigen tests (RATs) enabled 53% to 74% of college students to leave isolation early when they began isolation at the time of the first positive test, but 15% to 22% remained positive beyond the recommended isolation period.

The study included 323 infected college students living in university housing; undergraduate students were required to screen upon arrival on campus and then twice weekly on designated days. Testing took place between Jan 1 and Feb 11, 2022, during the Omicron surge in the United States.

Positive students were expected to isolate for 10 days, or 5 days if they received a negative RAT, following new Centers for Disease Control and Prevention guidelines. Upon testing negative, students ended isolation but continued mandatory masking until day 10.

"We found a day 5 positivity of 47% in the twice-weekly screening group and 26%–28% in the less frequently screened groups," the authors wrote.

Negative RAT tests on day 5 allowed 78% to 85% of students to confidently leave isolation, the authors said. The percentage remaining positive dropped to 6% to 8% on day 7.

Unexpectedly, the authors found that students who had received three or more COVID-19 vaccine doses had longer RAT positivity duration than students with only the primary series. The authors posit this could be a finding based solely on the transmissibility of the Omicron variant.

The Maricopa County Department of Public Health (MCDPH) in Arizona this week reported a dengue infection in someone who was probably exposed to an infected mosquito in Maricopa County.

Mosquito surveillance has detected dengue virus in a mosquito trap in one of the county's neighborhood, the MCDPH said in a Nov 14 press release.

Health officials are distributing free at-home blood tests in the neighborhood and are looking for more virus in mosquito traps in the rest of the county. The county is stepping up efforts to educate people on how to prevent the disease.

The case appears to be the first locally acquired dengue infection in Maricopa County. All earlier infections had been linked to international travel. Also, the case appears to be the first local dengue infection on the US mainland outside of Florida, which has reported 41 such cases this year, according to the latest arbovirus surveillance report from the Florida Department of Health.

In its background information, the Centers for Disease Control and Prevention (CDC) said most outbreaks in the United States have been small and limited, but the types of mosquitoes that spread the virus are in many parts of the country, posing a risk of local spread