Varicella Vaccine Highly Effective in Preventing Chickenpox

The varicella vaccine is highly effective in protecting children against chickenpox for many years, researchers say.

Chickenpox is a viral infection caused by the varicella zoster virus. The highly contagious disease spreads via air, when the infected person sneezes or coughs, or when a person comes in direct contact with fluid from the blister. Children below 10 years of age are at a greater risk of developing the itchy fluid-filled blisters than others.

The chickenpox vaccine was first introduced in the United States in 1995. According to CDC, before the vaccine, about four million people used to get chickenpox and about 150 people would die every year. In 2006, a second dose of the vaccine was introduced in the U.S.

To check the vaccine's efficiency, researchers from the Kaiser Permanente Vaccine Study Center followed more than 7,500 children for 14 years. All the participants received the vaccine between the age of 1 and 2 years.

Chickenpox cases among children had come down considerably after the introduction of the vaccine. However, a minority of 1,505 cases developed the disease even after taking the vaccination, termed as breakthrough cases. But, the severity was much lesser compared to children who developed chickenpox before the introduction of the vaccine. Over the years, particularly after the introduction of the second dose in 2006, the breakthrough cases also declined dramatically.

"Clearly, the vaccine is a very effective tool in preventing or limiting the severity of chicken pox in young people. As with any vaccine, though, the rate of vaccination has a huge impact on effectiveness. The more children vaccinated, the more effective the vaccine is for the entire community," Randy Bergen, chief of outpatient pediatrics at Kaiser Permanente's Walnut Creek Medical Center, said in a news release.

"Keeping vaccination rates high confers benefit on the community as a whole because there are fewer children who can contract and spread the virus."

The findings of the study will be published in the online issue of Pediatrics.