Ensuring Immunity to Varicella in Healthcare Workers

Download PDF version formatted for print: Ensuring Immunity to Varicella in Healthcare Workers (PDF:30KB/2 pages)

On this page:
Healthcare workers' varicella immune status should be evaluated
Vaccination recommendation for healthcare workers
If a healthcare worker has documented immunity does he or she have to take any additional precautionary steps when exposed to varicella?
What is recommended for unvaccinated healthcare workers without evidence of immunity who are exposed to varicella?
Should healthcare workers be tested after vaccination to ensure immunity?
Lab tests for immunity to varicella
Are recently vaccinated healthcare workers at risk for transmitting vaccine virus to susceptible persons?

To prevent nosocomial spread of varicella zoster virus, healthcare facilities should ensure that all healthcare workers have evidence of immunity to varicella. The national Advisory Committee on Immunization Practices (ACIP) recently revised the criteria for evidence of immunity to varicella. ACIP recommendations for the Prevention of Varicella. Attention: Non-MDH link

Healthcare workers' varicella immune status should be evaluated

The ACIP, with support from the Healthcare Infection Control Practices Advisory Committee (HICPAC), recommends that healthcare institutions ensure that all healthcare workers have evidence of immunity to varicella. For these workers, evidence of immunity includes any of the following:

  • Documentation of two doses of varicella vaccine;
  • Blood tests showing immunity due to a history of disease; or
  • Documented history from a healthcare provider of a) diagnosis of varicella (chickenpox) or zoster (shingles); or b) verification of a history of varicella or zoster.

Note: Birth before 1980 is not considered evidence of immunity for healthcare workers.

Serologic screening before vaccination of staff that have negative or uncertain history of varicella disease is likely to be cost effective. Most adults (70-90%) who do not remember having chickenpox are actually immune.

Institutions may elect to test all healthcare workers regardless of disease history because a small proportion of persons with a positive history of disease might be susceptible.

Vaccination recommendation for healthcare workers

MDH, based on current ACIP recommendations, encourages two doses of varicella vaccine for healthcare workers without evidence of immunity. Priority should be based on risk of non-transient, face-to-face contact with varicella cases (e.g., outpatient clinics, emergency departments) and patient population served (e.g., obstetrics and immune compromised patients). Healthcare worker age may also be a factor in prioritization. (Serologic studies have shown that nearly all U.S.-born adults born before 1977 have been infected with VZV.)

If a healthcare worker has documented immunity, does he or she have to take any additional precautionary steps when exposed to varicella?

If a healthcare worker is exposed to varicella, he or she should consult with the facility's occupational health department. Even if the healthcare worker has received 2 doses of varicella vaccine, they should be monitored daily for 10 – 21 days post-exposure. They should report any symptoms to the occupational health department without delay. This is particularly important if the exposed healthcare worker is going to care for immunocompromised individuals.

What is recommended for unvaccinated healthcare workers without evidence of immunity who are exposed to varicella?

Unvaccinated healthcare workers without evidence of immunity or vaccination history are potentially infective from days 10 – 21 post-exposure. They should be furloughed during this period; post-exposure vaccination is recommended within 3 – 5 days of exposure since it may attenuate the disease if infection occurs. If the exposure did not cause infection, vaccination more than 5 days after exposure is still indicated as it induces protection against subsequent infection. A second dose of vaccine should be administered at least 4 weeks after the first dose. Exposed healthcare workers who have received 1 dose of vaccine and who are exposed to VZV should receive a second dose of vaccine within 3 – 5 days post-exposure (provided a minimum of 4 weeks has elapsed since the first dose).

Should healthcare workers be tested after vaccination to ensure immunity?

Routine testing of healthcare workers for varicella immunity following two doses of vaccine is not recommended. Available commercial assays are not sensitive enough to detect antibody after vaccination in all instances. Sensitive tests have indicated that 99% of adults develop antibodies after the second dose. However, seroconversion does not always result in full protection against disease, and no data regarding correlates of protection are available for adults.

Lab tests for immunity to varicella

The two most commonly used tests to detect varicella IgG antibody among healthcare workers after natural infection are latex agglutination (LA) and ELISA.  Although the LA test is generally more sensitive than commercial ELISAs, a recent report indicated that the LA test can produce false-positive results, particularly when only a single concentration of serum is evaluated. Therefore, for the purpose of screening healthcare workers for varicella susceptibility, a less sensitive and more specific commercial ELISA should be considered.

Are recently vaccinated healthcare workers at risk for transmitting vaccine virus to susceptible persons?

The risk of transmission of vaccine virus from persons who develop a varicella-like rash after vaccination is low, and has been documented only after exposures in households and between residents in long-term care facilities. No cases associated with vaccination of healthcare workers have been documented. As a safeguard, precautions should be taken for all healthcare workers that develop a rash after vaccination. These individuals should avoid contact with anyone without evidence of immunity who may be at risk for severe disease and complications until a) all lesions resolve (i.e., crusted over or faded away); or b) no new lesions appear within a period of 24 hours – whichever is longer.

 

Updated Wednesday, May 28, 2014 at 02:45PM