FAQ: Varicella vaccination prevents disease spread
FAQ: Varicella vaccination prevents disease spread
Common questions answered on HCV vaccination
The Centers for Disease Control and Prevention (CDC) recommends varicella vaccination for susceptible health care workers, especially if they have close contact with patients who are at high risk for serious complications. That includes premature infants born to susceptible mothers, infants who are born at less than 28 weeks of gestation or who weigh less than 1,000 g at birth (regardless of maternal immune status), pregnant women, and immunocompromised people.
These answers to common questions were provided by Francisco Averhoff, MD, Adriana Lopez, MD, and Dalya Guris, MD, of the CDC’s National Immunization Program:
Question: How effective is the varicella vaccine?
Answer: Greater than 90% of susceptible, healthy adults seroconvert following two doses of varicella vaccine while only 80% seroconvert after a single dose. Seroconversion does not always result in full protection against disease. Effectiveness, the "real world" protection against disease, has been found to be 80% to 85% against any disease and greater than 95% against severe disease. (These studies were done in children.)
Question: Can health care workers still transmit varicella if they have been vaccinated and have a breakthrough infection?
Answer: Yes, varicella is transmissible following breakthrough infections among vaccinated individuals. However, there are some differences. Vaccinated cases with less than 50 chickenpox lesions are one-third as contagious to susceptible individuals as nonvaccinated cases. Vaccinated cases with 50 or more lesions are equally contagious as nonvaccinated cases.
Question: If a health care worker is exposed to varicella but has been previously vaccinated, do I need to perform serologic testing for immunity?
Answer: Testing vaccinees for seropositivity is a potentially effective strategy for identifying vaccinated people who remain at risk for varicella as varicella is unlikely to develop in people who have detectable antibody.
Question: How should I manage health care workers who develop a rash after varicella vaccination?
Answer: A rash following vaccination occurs in 4% to 6% of vaccine recipients and typically less than 10 lesions develop. Generally, if rash develops within two weeks of vaccination, it is more likely to be a wild-type varicella infection than a vaccine-associated rash. Vaccinated people who develop a rash caused by vaccine have a small risk of transmitting vaccine virus to healthy contacts, but immunocompromised people may have a higher risk of being infected with the vaccine virus. HCWs who develop a rash following vaccination should not have direct patient contact until scabs develop on all lesions.
Question: Should varicella vaccine be used as postexposure prophylaxis of health care workers?
Answer: Yes, it should be offered to susceptible HCWs (those with a negative history of disease and never vaccinated). Varicella vaccine is 90% effective in preventing disease if given within three days of exposure and 70% if given within five days. It is 100% effective in modifying (attenuating) the disease if given within five days.
Question: What do you recommend if a pregnant health care worker is exposed inadvertently to varicella but does not have a history of immunity? What if she was previously vaccinated?
Answer: A pregnant HCW who is susceptible to varicella should be offered VZIG (varicella zoster immune globulin). VZIG has been shown to prevent viremia, fetal infection, congenital varicella syndrome, and neonatal varicella. If she has been previously vaccinated, she should be considered immune and no action is necessary. If there is doubt about her immunity, her antibody titer can be tested to determine if she is susceptible.
Question: What is considered reliable history of chickenpox?
Answer: There is no definition of what is or is not a reliable history of chickenpox. Studies have shown that if people give a history of having had chickenpox (as reported by the parent/self/health care provider), serologic testing confirms that this is predictive of immunity (past infection) more than 90% of the time. This is because in the past, chickenpox infection was almost universal in the United States (most children had the infection by age 10). But as the incidence of disease continues to decrease, the positive predictive value of a history of chickenpox may become less reliable.
Question: How long will vaccine protection last? Will health care workers need revaccination?
Answer: Studies found that among susceptible healthy adults who were vaccinated and followed for 13 years, 9% to 21% had breakthrough varicella infections (depending on exposure history). Varicella infections tend to be much milder among vaccinated people. There are no recommendations for revaccination of HCWs at this time.
The Centers for Disease Control and Prevention (CDC) recommends varicella vaccination for susceptible health care workers, especially if they have close contact with patients who are at high risk for serious complications. That includes premature infants born to susceptible mothers, infants who are born at less than 28 weeks of gestation or who weigh less than 1,000 g at birth (regardless of maternal immune status), pregnant women, and immunocompromised people.Subscribe Now for Access
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