Chickenpox Becoming Rarer Thanks to Two-Dose Vaccine

Chickenpox Becoming Rarer Thanks to Two-Dose Vaccine
This child is covered in a red rash, one of the main symptoms of chickenpox. Photo courtesy Buchanan.

Chickenpox was once a rite of passage in childhood, with many adults carrying a small chickenpox scar to this day. However, new data shows that thanks to a two-dose vaccine, chickenpox is becoming much rarer in the United States.

The report, called Epidemiology of Varicella During the 2-Dose Varicella Vaccination Program, was released September 2nd in the Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR). The report examined the number of chickenpox cases in the U.S. since doctors began recommending the two-dose varicella vaccine schedule in 2006 compared to the number of cases with the older, single-dose vaccine. To do this, the researchers used information from the National Notifiable Diseases Surveillance System (NNDSS), in which state health departments report data on chickenpox and other diseases to a central database.

In the U.S. in the early 1990s, about 4 million people had chickenpox each year. Although most children who get chickenpox will experience mild symptoms, like an itchy rash with blisters along with a fever and feeling tired, some people are more at risk. The disease poses a risk to adults, babies, and anyone with a weakened immune system. In fact, in the early 1990s, an average of 13,500 people a year were hospitalized with chickenpox, and between 100 and 150 people a year died from the infection.

Although chickenpox can be risky, the vaccine can help. Those who get a vaccine tend to have a milder case of chickenpox if they do catch it, with fewer skin blisters. Children used to receive a single dose of the varicella vaccine, but armed with newer information, doctors began recommending giving children two doses of the vaccine, one between 12 and 15 months of age and the other between 4 and 6 years of age.

In the 10 years since 1996, a single-dose vaccine decreased the number of chickenpox cases in the U.S. by 84.6 percent. Between 2006 and 2015, thanks to the introduction of the two-dose vaccine, the CDC says the number of chickenpox cases have dropped an additional 84.6 percent. This reduction was most noticeable in children aged 5 to 14, who were most likely to have received the two vaccine doses, at an 89.3 percent decrease in ages 5 to 9 and 84.8 percent decrease in ages 10 to 14.

The researchers discovered that 55% of all chickenpox cases were people who had been vaccinated. Of the people who did become ill with chickenpox, only 23.2 percent of unvaccinated patients experienced a mild form of the disease while 76.8 percent of the vaccinated patients experienced a mild form of the disease. This seems to confirm that even if someone who was vaccinated for chickenpox does get sick, they will be less sick than if they had not been vaccinated.

There were some limitations with the CDC data, however. Not all states are reporting data to the CDC, and even when they do, all chickenpox cases may not be reported to a doctor and patients may not always be tested to confirm a diagnosis. Mild forms of chickenpox can also be mistaken for a different illness if few skin lesions are present.

The data is encouraging as it shows that vaccines can have a huge effect on disease. As common as chickenpox has been in the past, it is becoming more rare, and also milder, as vaccines are improved. With continued use of the vaccine, chickenpox could some day be as rare as polio and other diseases which have almost been eliminated from the population.

Chickenpox is a highly contagious disease, caused by the varicella-zoster virus (VZV). Before any rash appears, chickenpox patients will usually experience symptoms like a fever, headache, stomach ache, and sore throat. The red, itchy rash will then appear usually on the abdomen, back, or face, next spreading to other areas of the body such as the arms, legs, scalp, genitals, and mouth. The rash will first appear as small, red bumps, but then they will blister and fill with fluid. When the blisters break, there will be open sores, which then form scabs. In addition to being unsightly, the rash is extremely itchy, and if the patient scratches the itchy lesions, they can form a scar. Rarely, someone with chickenpox can develop a serious bacterial infection in their skin, bones, joints, lungs, and brain. For a mild form of the disease, the patient can visit their doctor to confirm a diagnosis, but treatment usually just involves an over-the-counter fever drug and calamine lotion to combat the itchiness. A child should stay home from school and avoid adults, babies, and other vulnerable people who have not yet had chickenpox, since the disease is highly contagious.

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