Strep's variations make vaccine elusive – so far

Q: There are vaccines available for quite a few bacterial diseases and infections, but we still don't have one to protect against strep throat. Is there a reason the pharmaceutical companies have yet to develop such a vaccine, despite the obvious need for it?

A: Although researchers and drug manufacturers have been working to crack the code of a global strep vaccine for several decades, success has proved elusive. That may be why their efforts have mostly flown under the radar. In recent years, as various research teams announced breakthroughs, there has been a sense the goal may be in sight. However, as you point out, a global strep vaccine has yet to become available. This is due in large part to the nature of strep bacteria.

Strep is short for streptococcus. Although there are several types, most illnesses are caused by group A or group B strep. When someone is diagnosed with strep throat, it's a group A infection. The bacteria travels on the respiratory droplets an infected person releases when sneezing, coughing or speaking.

While strep throat is the best-known illness this bacteria causes, it's not the only one. A range of other diseases, including the skin infections impetigo and cellulitis, are caused by strep A. In these cases, direct contact with an infected sore, or secretions from the sore, can also transmit the bacteria. Other serious illnesses driven by strep A include scarlet fever, rheumatic fever, rheumatic heart disease, necrotizing fasciitis and toxic shock syndrome.

Group B strep can cause blood infections, pneumonia and meningitis in newborns. Older adults, particularly those with existing health problems, are also vulnerable to strep B. This includes urinary tract or skin infections and pneumonia.

Worldwide, more than 750 million people fall ill from a group A strep infection each year. It causes at least 500,000 deaths per year, mostly in areas of low income. The only treatment is the use of antibiotics.

Among the challenges of developing a vaccine against strep is the bacteria's diversity. There are more than 200 different known strains of strep A. Each has a slight but crucial structural difference, which the immune system must learn before it can mount a successful defense. In order to develop an effective vaccine, researchers must identify a characteristic in strep A that is universal to all strains. This has proved to be a steep hill to climb.

At the same time, strep A bacteria lacks an external membrane. This leaves it extremely vulnerable to the effects of antibiotics, including penicillin. In nations with robust health care systems, this vulnerability makes it fairly easy to treat a strep A infection with a course of antibiotics. It also lowers the interest in a vaccine. But in poorer nations, where people often have little or no access to medical resources, the annual burden of strep infections remains severe.

Now, with the growing threat of antibiotic resistance, a new urgency has entered the search for a strep vaccine. It makes the outcomes of the clinical trials currently in progress important to everyone.

Symptoms of esophageal cancer can be easy to dismiss

Q: A family friend is suddenly on hospice care because of esophageal cancer, which has spread to his lungs and liver. The thing is, he never even knew he had it. Other than getting the hiccups and losing some weight, he was fine. What causes this cancer? How common is it?

A: Cancer of the esophagus is the eighth-most-common cancer worldwide. Although it is seen less often in the United States, cases here are gradually increasing. According to the National Cancer Institute, esophageal cancer accounts for slightly more than 1% of new cancer diagnoses in this country. It is estimated there will be 20,640 new cases of esophageal cancer diagnosed in the U.S. this year, and there will be about 16,400 deaths from the disease. This form of cancer is more common in men than in women, and it is also associated with older age. The majority of cases are diagnosed after age 55.

The esophagus is the hollow passageway that connects the mouth and throat to the stomach. It's about 9 to 10 inches long in adults and has muscular walls that contract and relax as they move the food and drink you swallow from the mouth to the stomach.

While the esophagus itself is fairly sturdy, it is lined with delicate tissues known as the mucosa. These are vulnerable to inflammation, including from acid reflux, and potentially harmful substances, including alcohol and tobacco. In fact, heavy alcohol use, smoking and chronic acid reflux are risk factors for developing esophageal cancer.

A handful of recent studies have uncovered a possible link between drinking scalding-hot beverages and the risk of developing this type of cancer. In 2018, researchers in China found a measurably higher incidence of esophageal cancer among both smokers and consumers of alcohol who also drank very hot tea.

This year, researchers in England found a similar connection to drinking very hot coffee. In their analysis of the health records of about 500,000 adults, they found that individuals who regularly drank very hot coffee had nearly triple the risk of this type of cancer. This differed from the Chinese study because it was independent of the use of either alcohol or tobacco. As for why this might be, researchers have theorized that consuming hot liquids damages the lining of the esophagus. They suspect that repeated injury and ongoing inflammation leave the delicate tissues vulnerable to the effects of potential carcinogens.

The five-year survival rate for this type of cancer is just 20%. This is partly because, as in your friend's case, it can be asymptomatic and often isn't caught early. Fewer than 18% of esophageal cancers are caught in the early stage, when the disease is localized.

When discovered at an early stage, the five-year survival rate rises to 50%. But the early symptoms, which include indigestion, heartburn or difficulty while swallowing, can be easy to dismiss. Additional symptoms include ongoing hoarseness, unexpected choking on food, unexplained weight loss and pressure or pain behind the breastbone or in the throat. When someone begins to experience these symptoms and they don't go away, they should check in with their health care provider.

• Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu.