Fungal infections are increasingly common. Why is there no vaccine?

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

While scientists aren’t worried that a fungal infection like the one seen in HBO’s “The Last of Us” will wipe out humanity, infections are certainly cause for concern.

Fungi cause a wide range of illnesses in humans, from irritating athlete’s foot to life-threatening blood infections.

In the United States, fungal infections are responsible for more than 75,000 hospitalizations and nearly 9 million outpatient visits each year, according to the Centers for Disease Control and Prevention. In 2021, about 7,200 people died from fungal diseases. Those numbers, the CDC said, are likely an underestimate.

A type of mushroom, candida auris, can be resistant to all the drugs used to treat it, and is particularly dangerous for patients in hospitals and nursing homes. The fungus was first identified in Japan in 2009 and has since been found in more than 30 countries, including the United States, the CDC said.

Climate change also threatens to spread several infectious fungi: the fungus that causes valley fever thrives in warm, dry soil, and the fungus that causes a disease called histoplasmosis prefers high humidity.

Despite the growing threat, there are currently no licensed vaccines — in the United States or abroad — to prevent fungal infections.

“These are the most important infectious diseases you haven’t heard of,” said Karen Norris, an immunologist and vaccine expert at the University of Georgia. “A vaccine has the potential to advance and protect a wide range of individuals.”

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

But a “pan-fungal” vaccine is incredibly difficult to make.

This is because, she said, unlike Covid vaccines, which target a single pathogen – the SARS-CoV-2 virus – a fungal vaccine would ideally protect against the broad spectrum of existing fungi, each biologically different l each other.

For now, Norris and his team have decided to focus on the three fungi responsible for the vast majority of fatal fungal infections in the United States:

• Aspergillusa common mold that can cause an infection of the lungs and sinuses which can then spread to other parts of the body.
• candidiasisnotably candida auris, a type of yeast that can cause serious blood infections, especially in people in health care settings.
• Pneumocystiswhich can cause pneumonia.

In preclinical trials, the experimental vaccine developed by Norris and his team has been shown to generate antifungal antibodies in animals, including rhesus macaques. With financial support, researchers could begin and complete human vaccine trials within the next five years, she said.

In Arizona, researchers are focusing on a vaccine to prevent Valley fever, a lung infection caused by the fungus Coccidioides. The fungus, typically found in hot, dry soils in the southwest, is an “emerging threat,” Norris said, as climate change expands its range.

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

While experts know which fungi are the best to target, vaccine development has been slow, mainly due to a lack of funding, said Galgiani, who is working to start a human trial for the vaccine against the disease. Valley fever.

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

By comparison, hundreds of species of fungi can cause disease in humans, but the most common ones – such as those that infect the skin and nails, or cause yeast infections or athlete’s foot – do not life-threatening, according to Galgiani.

Additionally, severe cases are sporadic in the United States, he said.

Valley fever, for example, is generally limited to southern and western regions of the United States and is usually severe for people with weakened immune systems. Most people breathe Aspergillus every day without getting sick, but it can be deadly for people with cystic fibrosis or asthma. candida auris infections have been mostly confined to healthcare settings and pose the greatest threat to very sick patients.

“As a risk-reward investment proposition, it fails,” Galgiani said of developing a vaccine. “You wouldn’t put your retirement investment in there.” He said it could take eight years before a fungal vaccine is available in the United States.

But as awareness of the impact of climate change on fungal infections increases, financial support could increase and a fungal vaccine could be developed sooner, Norris said.

In response to growing public health concerns about serious and life-threatening fungal diseases, the National Institutes of Health released a framework in September outlining how the United States could create a valley fever vaccine within 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 a handful of oral treatments for most mild to moderate fungal infections. Depending on the fungus, he said, people may need to take the drugs for three to six months to clear the infection from their system. The drugs can cause side effects, including headache, stomach pain, vomiting, and diarrhea.

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

In severe cases, some people may need to take drugs intravenously, such as amphotericin B, he said.