Informing, immunizing HCWs for chickenpox

Program also can provide needed data during outbreaks

Infection control professionals in California have developed a screening and education program to ensure health care workers susceptible to varicella zoster virus (VZV) are aware of the risks and benefits of immunization.

Chickenpox, a highly contagious disease caused by VZV, causes a systemic infection that usually results in lifetime immunity. Though most cases occur in childhood, susceptible adolescents, adults, and immunocompromised people usually have more severe disease than children and are at higher risk for complications. Merck and Company Inc. , in Whitehorse Station, NJ, manufactures the Varivax vaccine, which uses a strain of live, attenuated varicella virus. Licensed in March 1995, the vaccine is approved by the Food and Drug Administration for use in healthy people at least a year old. Among those contraindicated for vaccination are the immunocompromised and pregnant women. In 1996, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) recommended vaccinating all health care workers susceptible to VZV unless otherwise contraindicated.1

To provide informed consent and identify risk factors, clinicians at Summit Medical Center in Oakland used available information and data from the package insert to develop an employee form and handout that can be used by other ICPs trying to develop similar programs. (See form and handout.) The goal is to immunize susceptible health care workers unless they have contraindications.

"We wanted to be very conservative when the vaccine was new, " says Patrick Joseph, MD, chief of epidemiology at the medical center. "But now we have several years of experience with the vaccine, and since it has proven to be safe and efficacious, it’s time to incorporate this into our daily work."

Have you had chicken pox?

The first step in undertaking such a program is to determine which employees remember having chickenpox and exclude them from the program.

"We screen all new employees for chickenpox by questionnaire," he explains. "If an employee says that he or she had chickenpox as a child, that is accepted as being valid and accurate. Any employee who says that they did not have chickenpox as child or is unclear is offered blood testing for documentation of immunity."

It is cost-effective to screen for immunity rather than proceeding to immunization because even those who do not recall childhood infection likely had chickenpox — possibly subclinically — and are naturally immune. Indeed, it is estimated that more than 90% of the adults in the United States are immune, but local demographics can alter that pattern considerably, Joseph reminds.

"In California, we have a large number of employees from the Philippines and Guam, and childhood chickenpox is not a common disease in the Pacific Islands," he says. "So actually in our setting if people say they have not had chickenpox as a child, they may be right. That’s why we get numbers as low as 60% to 70% [naturally immune with no memory of disease]."

Once a pool of susceptible workers has been identified, they can then be counseled about the vaccine and risk factors using the form and the handout. ICPs can use the form, for example, to ask a series of questions that can reveal underlying risk factors.

"They’re not [all] necessarily contraindications, but they are questions that require further explanation," he says. "So for example, if a person has had a previous allergic reaction to any vaccine or medicine, we just want to know. If it turns out they have had a severe reaction to neomycin — there is neomycin contained in the varicella vaccine — then that can be considered a contraindication."

Health care workers more often report an allergy to penicillin or another antibiotic that does not contraindicate VZV immunization, he adds. In addition, those who report cold, fever, or flu symptoms should wait to be vaccinated in order to ensure immunity is achieved, he says. Likewise, recent receipt of a blood transfusion could impair vaccine effectiveness because the blood could contain VZV antibodies acquired through childhood infection. Pregnancy is a contraindication because the vaccine uses live virus, which also prohibits its use in those with HIV or other immunocompromised conditions, Joseph reminds.

Documenting declinations

Under the program, susceptible employees who decline vaccination must sign a declination statement indicating they were informed of the risk and they agree to follow infection control precautions should an exposure occur. Such infection control measures traditionally have included worker furloughs, but the policy at Summit Medical allows workers to stay on the job if they wear a face mask during the incubation period (days 10 through 21 of the exposure). That approach is considered both low-risk and considerably more cost-effective than furloughing and replacing staff for extended periods, he notes.

"But during that period of time when one is likely to become infectious, if he or she develops a febrile illness, a respiratory illness, or anything suggestive of adult varicella, then they are work-furloughed," he says.

The policy thus far has been very cost-effective and has resulted in few worker furloughs, but it also includes a common-sense caveat about the subsequent duties of the exposed/masked worker.

"It’s also very important to consider the risk depending on the employee’s job," Joseph says. "For example, in a hospital where adult and pediatric [patients] are widely separated or there is no pediatrics [ward], the risk is relatively low. On the other hand, you would not want to take that risk on a pediatric ward or an oncology ward. So if an exposed employee was wearing a mask, ideally that person should be in a work environment where the risk to the patients is as low as possible. That is a common-sense addition to the policy that seems to work very well."

According to the CDC, children and adolescents under 15 years old account for some 80% of the estimated 9,000 annual varicella-related hospitalizations. The most common complications of varicella, which result in hospitalization, are bacterial infections of skin lesions, pneumonia, dehydration, encephalitis, and hepatitis.

A benefit of the screening and immunization program is ready access to data on immune and susceptible employees should chickenpox be introduced via an infected patient, Joseph says.

"At this time, at every facility where I work, we know the chickenpox-serologic status of everyone, and that certainly helps us with outbreak management."

Reference

1. Centers for Disease Control and Prevention. Prevention of varicella: Recommendations of the Advisory Committee on Immunization Practices. MMWR 1996; 45(No. RR-11):1-36.