A once-familiar childhood illness is disappearing as doctors recommend a second dose of the vaccine against chickenpox.

States that report vaccination data to the Centers for Disease Control showed an 85-percent drop in cases of the highly infectious disease since 2006, when doctors began routinely recommending a second dose of the vaccine for the varicella-zoster virus, which causes chickenpox, reported Health Day.

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The drop was most noticeable among children ages 5 to 14 years old, according to a new CDC report.

Chickenpox — which causes an itch, blistery rash — once afflicted an average of 4 million Americans a year as recently as the early 1990s.

About 13,500 patients were hospitalized with the virus, which caused 100 to 150 deaths a year.

The CDC credits vaccination with preventing more than 3.5 million cases of chickenpox each year, as well as 9,000 hospitalizations and 100 deaths.

A single-dose vaccine was introduced in 1996, which led to a 90-percent decline over the next 10 years, but doctors began recommending a second dose after continued outbreaks.

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Even in patients whose vaccinations fail to produce immunization, their chickenpox cases are milder than in those who have not had the vaccination.

Despite the success rates, anti-vaxxers continue to promote bogus claims that vaccines are unnecessary or even unsafe, and doctors are reporting that more Americans agree.

A recent survey found that about 87 percent of pediatricians had encountered vaccine refusals, up from 75 percent in 2006, and three-fourths of those parents said they believed vaccinations were unnecessary for diseases eradicated through widespread immunization.

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Another survey found that one in 10 Americans — especially those under 30 — actually believed vaccines were unsafe.