Fungal infections are becoming more common. Why is there no vaccine?

Fungal infections are becoming more common in the United States, but unlike diseases caused by bacteria or viruses, there is no vaccine to protect against the fungal threat.

Fungi cause a wide range of diseases in humans, from annoying athlete’s foot to life-threatening bloodstream infections..

According to the Centers for Disease Control and Prevention, fungal infections cause more than 75,000 hospital admissions and nearly 9 million outpatient visits each year in the United States. In 2021, about 7,200 people died from fungal diseases. Those numbers, according to the CDC, are likely underestimates.

One type of fungus candida golden, can be resistant to all drugs used to treat it, and is especially dangerous for hospitalized and nursing home patients. The fungus was first discovered in Japan in 2009 and has since been found in more than 30 countries, including the US, according to the CDC.

Climate change could also lead to a wider spread of some infection-causing fungi: the fungus that causes valley fever thrives in hot, dry soil, while the fungus that causes a disease called histoplasmosis prefers high humidity.

Despite the growing threat, there are currently no licensed vaccines – either in the US or abroad – to prevent fungal infections.

While scientists aren’t worried that a fungal infection like the one featured on HBO’s The Last of Us will wipe out humanity, the infections certainly are.

“These are the most important infectious diseases you haven’t heard of yet,” said Karen Norris, an immunologist and vaccine expert at the University of Georgia. “A vaccine could go a long way and protect a large number of people.”

Deadly fungal infections

Norris said the ultimate goal would be to develop a single vaccine that protects against all fungal infections.

But making a “panfungal” vaccine is incredibly difficult.

That’s because, she says, unlike Covid vaccines, which target a single pathogen — the SARS-CoV-2 virus — the antifungal vaccine ideally protects against a wide range of existing fungi, each biologically distinct from the other.

For now, Norris and her team have decided to focus on three fungi responsible for the vast majority of deadly fungal infections in the US:

  • Aspergilluscommon mold that can cause an infection in the lungs and sinuses that can later spread to other parts of the body.
  • candidaespecially candida auris, a type of yeast that can cause serious blood infections, especially in people in healthcare settings.
  • Pneumocystiswhich can cause pneumonia.

An experimental vaccine developed by Norris and her team has been shown in preclinical testing to produce antifungal antibodies in animals, including rhesus monkeys. With financial support, researchers can begin and complete human trials of the vaccine within the next five years, she said.

In Arizona, researchers are focusing on a vaccine to prevent valley fever, a lung infection caused by a fungus. coccidioids. The fungus, typically found in the hot, dry soils of the Southwest, is an “emerging threat” because climate change is expanding its range, Norris said.

So far, the vaccine has been shown to be effective in dogs, said John Galgiani, director of the Valley Fever Center of Excellence at the University of Arizona College of Medicine.

Little urgency, lack of funding

While experts know which fungi are best targeted, development of a vaccine has been slow, largely due to a lack of funding, said Galgiani, who is working to start human trials of the Valley Fever vaccine.

Many in public and private settings do not view antifungal vaccines as a “critical unmet need”. He said. Respiratory viruses, such as those that cause Covid, influenza or measles, infect millions of people and result in thousands of hospitalizations worldwide each year, he said. Viruses can be fatal to anyone in any part of the world, he said, highlighting the need for vaccines to prevent these diseases.

By comparison, hundreds of fungal species can cause disease in humans, but the most common ones, such as those that affect the skin and nails, or cause vaginal yeast infections or athlete’s foot, are not life-threatening, Galgiani said.

In addition, he said, severe cases in the US are sporadic.

Valley fever, for example, is usually limited to the southern and western regions of the United States and is usually dangerous for people with weakened immune systems. Most people inhale Aspergillus every day without getting sick, but it can be life-threatening for people with cystic fibrosis or asthma. candida golden infections have been largely confined to healthcare facilities and pose the greatest threat to very ill patients.

“As an investment proposal based on risk and reward, it is failing,” Galgiani said of vaccine development. “You wouldn’t put your retirement investment in that.” He said it could take eight years before a fungal vaccine is available in the US.

But as awareness grows about the impact of climate change on fungal infections, financial support could grow and a vaccine against the fungus could be developed sooner, Norris said.

In response to growing public health concerns about severe and life-threatening fungal diseases, the National Institutes of Health released a road map in September on how the US could develop a vaccine against valley fever in the next 10 years.

Last October, the World Health Organization released its first-ever list of fungi that pose the greatest threat to public health, calling for more research into 19 fungal diseases.

Dr. Andrew Limper, a pulmonologist at the Mayo Clinic in Rochester, Minnesota, said there are several oral medications for most mild to moderate fungal infections. Depending on the fungus, people may need to take medication for three to six months to clear the infection from the body, he said. The drugs may come with side effects, including headache, abdominal pain, vomiting, and diarrhea.

People with strong immune systems often recover with medication, he says, but fungal infections, especially those that affect the lungs, can leave scars.

In severe cases, some people may need intravenous medications such as amphotericin B in severe cases, he said.

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