CLINICAL MATTER
Shingles, also known as herpes zoster, is a common and potentially debilitating disease.
One in three people will develop shingles over their lifetime. Some will have more than one episode. Shingles is very painful when it occurs. Even worse, 10 to 20 percent of people with shingles can develop a chronic pain syndrome known as post-herpetic neuralgia. It can be a lifelong, debilitating pain with no good treatment.
While there are effective antiviral medications for shingles, these do not reliably prevent the development of post-herpetic neuralgia. For the longest time, there was no way to avoid this dreaded complication. Fortunately, two vaccines have already been developed that can prevent shingles and post-herpetic neuralgia.
Shingles is caused by the reactivation of the varicella zoster virus, the same virus that causes chickenpox. Even after a person with chickenpox recovers, the varicella zoster virus persists in the body. It lies dormant in the dorsal root ganglion, a part of the nerve that is located close to the spinal cord.
As we get older, our immune systems weaken and the varicella zoster virus can become active again. It starts to replicate within the nerve cells and it causes inflammation from the dorsal root ganglion going toward the skin. When the infection reaches the skin, the characteristic rash made up of vesicles (small fluid-filled sacs on the skin) erupts. These vesicles can look exactly like those of chickenpox but are limited to one side of the body in the distribution of the affected nerve. This creeping, belt-like distribution is what gives herpes zoster its name—herpes means “creeping,” while zoster means “belt” or “girdle.” Sometimes, the vesicles are very tiny or they coalesce and can be mistaken for a different disease, which can lead to a delay in diagnosis.
Because the inflammation of the nerve starts from inside the body, some people already develop pain prior to the appearance of the vesicles. Referred to as prodromal pain, this can begin up to two weeks before the characteristic rash appears. When the vesicles do erupt, only then is the diagnosis of herpes zoster typically made. It is important to see a doctor as quickly as possible from the time the rash appears. Antiviral treatment with oral acyclovir or valacyclovir works best if started within 72 hours. There is no role for topical antiviral treatment since these do not penetrate deep enough. The vesicular rash can be itchy and painful. Aside from the usual analgesics, some physicians start gabapentin, pregabalin, or other nerve pain agents.
Without antiviral treatment, the rash can last two to four weeks before the vesicles begin to dry and crust over. The wet lesions do shed varicella zoster virus and can cause chickenpox in people who have not had it. People who are immunocompromised or have not had chickenpox should stay away from someone with active herpes zoster. Unlike chickenpox, which can be transmitted by respiratory droplets, varicella zoster from shingles is transmitted only via contact, so good hand hygiene is important, especially after handling the lesions or items that have been in contact with them. Residual pain is common up to three months after the lesions have dried. Unfortunately, up to 30 percent of patients will develop post-herpetic neuralgia in the distribution of the rash and this can last for months to years.
Aside from post-herpetic neuralgia, other complications can arise from herpes zoster. One of the most common occurrences is bacterial superinfection of the rash. This happens when the vesicles burst and skin bacteria infect the raw skin. Putting all sorts of ointments on the rash can also increase the risk of bacterial infection, so it is best to talk to your doctor before putting anything on the vesicles. Bacterial infection can become severe and can cause sepsis and scarring. Washing the skin lesions with soap and water is the best way to keep them clean. Pat dry with a fresh towel. If the vesicles look infected with bacteria and have a purulent discharge, see your doctor as soon as possible.
Herpes zoster can affect the eyes. Known as herpes zoster ophthalmicus, it can cause blindness. A medical emergency, it may require inpatient confinement and intravenous acyclovir. Herpes zoster of the face can come from the trigeminal nerve and cause extreme pain on one side of the face known as “tic douloureux,” which can be debilitating. Another form of facial herpes zoster can cause Ramsay-Hunt syndrome, which includes severe ear pain and one-sided facial paralysis. A recent episode of herpes zoster is also associated with a higher risk of stroke and heart attack.
Due to how common herpes zoster is and the severity of its complications, an effective vaccine that prevents both reactivation of the varicella zoster virus and subsequent postherpetic neuralgia is highly desirable. Herpes zoster, being a reactivation of the virus, is a bit more difficult to prevent using a vaccine than other infectious diseases. The major risk factor for herpes zoster is the decrease in immune function that occurs with age, termed immune senescence. When the immune cells and, to a lesser extent, the antibodies that keep the varicella zoster virus at bay become less potent and less in number, the virus breaks through and causes the disease. People above the age of 50 years old, who have had chickenpox infection, are at significant risk for herpes zoster. While many people cannot remember whether they have had chickenpox in the past, most studies checking for varicella zoster antibodies show that more than 90 percent of people age 50 and older show evidence of past infection.
The first successful attempt at making an effective vaccine for herpes zoster employed a live virus identical to the strain used for the chickenpox vaccine, albeit with a much higher dose of live virus to stimulate the waning immunity of elderly patients at risk. While the live vaccine was effective in preventing post-herpetic neuralgia, it was only moderately successful at preventing herpes zoster disease, and the efficacy waned below 50 percent after five years. It could also not be used for those with weak immune systems such as people living with HIV, organ transplant recipients, and cancer patients on immunotherapy because of the risk of causing actual disease.
A new vaccine, made up of a viral protein combined with a potent immune stimulator, was subsequently developed and shown to be 97 percent effective in preventing herpes zoster events as well as postherpetic neuralgia. The new vaccine seems to remain 89 percent effective over 10 years and is safe to use in those with weak immune systems since it isn’t a live vaccine. It is now available locally after several years of a global shortage. People above 50 years old should seriously consider receiving the herpes zoster vaccine. Those with weak immune systems and chronic illnesses may also benefit from vaccination. Herpes zoster is such a terrible disease with no good options that the best way to deal with it is not to get it in the first place. Talk to your doctor to see if getting vaccinated against shingles is right for you.