"I deeply regret that parents who are trying to do the right thing just don't get it," Cooper said. "The fact is that they're right, chickenpox for most children is a mild illness. But when you see children who have the misfortune of one of the complications that are possible, you never forget it."
Cooper said that he has seen children contract conditions as serious as encephalitis, a brain infection, and has even had young patients die from the virus after developing flesh-eating bacteria.
"The child does not need to be immune-deficient or malnourished to have these complications," said Cooper, who recommends that all parents vaccinate their children against the virus. "It can be an ordinary healthy child, it's Russian roulette."
Dr. Paul Offit, a pediatrician specializing in infectious disease at the department of pediatrics at the Children's Hospital of Philadelphia, said that many parents who are against vaccinating their children argue that getting the virus naturally is more beneficial to the child's overall health.
"The thinking many parents have is that the natural infection is more likely to induce higher levels of antibodies and longer-lasting immunity than vaccines," Offit said. "That's generally true but the problem is if you make that choice you are also taking the risk of a natural infection, which can mean hospitalization and sometimes death."
Parents who refuse to vaccinate their children can also be a public health risk, said Cooper, who said that other strains of the chickenpox epidemic can be passed around as children who are not protected against the virus mingle with one another.
"You don't know who goes to a chickenpox party and might have some sort of immunity or may have a complication from it or who might spread it to someone else who, because of the medication they're on or because they're pregnant, are very susceptible to the disease," Cooper said. "Not vaccinating kids just spreads all the risks that are the reason the vaccine was created in the first place."
Researchers now say the chickenpox vaccine has slashed the occurrence of the disease in children by 90 percent but still worry that parents like Carrie are preventing the virus from disappearing all together.
Offit believes that if the chickenpox vaccine becomes as widely used as the measles vaccine was back in 1963, chickenpox would go the way of the measles: away.
"When we introduced the measles vaccine, which is another virus that gets worse for patients as they get older, in 1963, we dramatically reduced the instance of measles," Offit said. "That is what will happen here with chickenpox."
But Carrie doesn't agree. She says that the fact that some children still get the virus despite being vaccinated is evidence that chickenpox will never disappear completely.
"Something like this will continually mutate and potentially be worse than before," Carrie said. "Kind of the way the overuse of antibiotics has happened."
As for what doctors say about how parents who don't vaccinate their children might be putting them at increased risk, Carrie is unconvinced.
"Everything you do every day puts my child at risk," she said. "Putting her in a car puts her at risk.
"We can all only make the decisions that are right for our families, and this is what happens to be right for my family at this moment in time."