Chickenpox is significantly more dangerous for adults than for children. What’s typically a mild, itchy nuisance in kids can lead to pneumonia, brain inflammation, and hospitalization in grown-ups. Before the U.S. vaccination program began in 1995, about a third of all chickenpox hospitalizations and roughly half of all deaths occurred in adults, despite adults making up a small fraction of total cases.
Why Adults Get Sicker Than Children
In children, chickenpox usually runs its course as a few days of fever, fatigue, and an itchy rash. Adults tend to experience a more aggressive version. The illness often starts with one to two days of fever and general malaise before the rash even appears, a “warning phase” that children rarely notice. Once the rash shows up, it progresses quickly from flat red spots to raised bumps to fluid-filled blisters before crusting over.
Adults typically develop more lesions, higher fevers, and longer illness duration. The immune system’s stronger inflammatory response in adults, which is usually an advantage, works against you here. It ramps up inflammation throughout the body, which is why complications involving the lungs and brain are far more common in adult cases.
Pneumonia: The Most Common Serious Complication
Varicella pneumonia is the leading cause of complicated chickenpox in adults, occurring in roughly 1 in 400 adult patients. It typically develops three to five days after the rash appears. Symptoms include cough, shortness of breath, rapid breathing, and sometimes chest pain. Chest imaging reveals widespread inflammation in both lungs, with patchy, hazy areas or small nodules scattered throughout.
In most cases, the lung inflammation resolves as the rash clears up. But some people are left with tiny calcified spots in their lungs that show up on X-rays for years afterward. For people who smoke or have underlying lung conditions, varicella pneumonia can become life-threatening and may require hospital-level care.
Neurological Complications
Chickenpox can also affect the brain and spinal cord, though this is less common than pneumonia. The virus can cause encephalitis (brain inflammation with impaired consciousness), meningitis (inflammation of the protective membranes around the brain and spinal cord), and cerebellar ataxia, which affects coordination and balance. These complications can develop during the acute infection or appear shortly after the rash resolves.
A Japanese surveillance study published in Emerging Infectious Diseases found that central nervous system complications from the varicella virus have been increasing among adults in recent years, with meningitis accounting for the majority of cases. While most people recover from these neurological complications, they can require hospitalization and may leave lasting effects in severe cases.
Risks for Immunocompromised Adults
Adults with weakened immune systems face the highest risk. This includes people with leukemia or lymphoma, those on chemotherapy, anyone taking high-dose steroids for more than two weeks, and people with other conditions that suppress immune function. In these patients, the virus can spread to internal organs, causing pneumonia, liver inflammation, encephalitis, and dangerous blood clotting problems.
The rash itself behaves differently in immunocompromised adults. New blisters may keep appearing for more than a week (compared to a few days in healthy adults), lesions can show up on the palms and soles where they don’t normally appear, and the blisters may fill with blood rather than clear fluid. These patients require intravenous antiviral treatment rather than the oral medication used for otherwise healthy adults.
Pregnancy and Chickenpox
Chickenpox during pregnancy poses risks to both the mother and the baby. Pregnant people are more likely to develop pneumonia from the infection, and the pneumonia tends to be more severe than in non-pregnant adults.
For the baby, the timing of infection matters. If chickenpox develops during the first 20 weeks of pregnancy, there is a small risk of congenital varicella syndrome, a group of serious birth defects affecting the skin, eyes, brain, limbs, and digestive tract. The risk window is highest between weeks 8 and 20. If infection occurs in the days or weeks just before delivery, the baby may be born with neonatal varicella, a potentially life-threatening condition that can also develop if the newborn catches chickenpox in the first few weeks of life.
Treatment Timing Is Critical
Antiviral medication is the standard treatment for adults with chickenpox. For healthy adults, the typical course is an oral antiviral taken four times daily for five days. The key detail: treatment needs to start at the earliest sign of illness, ideally within 24 hours of when symptoms first appear. There is no evidence that starting the medication later than 24 hours after symptom onset provides meaningful benefit.
This narrow window means that adults who suspect they’ve been exposed to chickenpox and start developing fever or malaise should seek medical attention quickly, before waiting for the rash to fully develop. For immunocompromised patients, treatment is given intravenously in a hospital setting regardless of timing.
Long-Term Risk: Shingles
Anyone who has had chickenpox carries the virus in their nerve cells for life. The virus lies dormant and can reactivate decades later as shingles, a painful blistering rash that follows the path of a single nerve. About one in three people who had chickenpox will eventually develop shingles, most commonly after age 50. Whether getting chickenpox as an adult rather than as a child changes your shingles risk isn’t well established, but the reactivation risk exists regardless of the age at which you were first infected.
Vaccination for Adults Without Immunity
The CDC recommends two doses of the varicella vaccine for adults who don’t have evidence of immunity, given four to eight weeks apart. Two doses are about 90% effective at preventing chickenpox entirely, and even more effective at preventing severe disease in the small number of vaccinated people who do get infected.
Evidence of immunity means one of several things: documented proof of two vaccine doses, a blood test showing antibodies, a healthcare provider’s confirmation that you had chickenpox previously, or being born in the United States before 1980 (when nearly universal childhood infection made natural immunity almost certain). If you’re unsure whether you had chickenpox as a child, a simple blood test can check for antibodies. Adults who have never had chickenpox or been vaccinated are the most important group to protect, since they face the full brunt of adult-severity disease if exposed.
How Hospitalization Patterns Have Shifted
The U.S. varicella vaccination program, now spanning over 25 years, has reduced chickenpox hospitalizations by 94% and deaths by 97% among people under 50. But the decline has not been equal across age groups. Hospitalizations among children dropped by 97%, while the decline among adults aged 20 to 49 was 85%. For adults over 50, hospitalization rates dropped only 31% to 41%.
This uneven pattern has changed who ends up in the hospital with chickenpox. In the early 1990s, adults over 50 accounted for just 5% of all chickenpox hospitalizations. By 2018 to 2019, they represented 44%. Similarly, between 54% and 85% of all chickenpox deaths since 2001 have been in people over 50. The takeaway is straightforward: chickenpox in adults, particularly older adults, remains a serious and sometimes fatal disease even in the vaccine era.