Chickenpox, caused by the varicella-zoster virus (VZV), is a highly contagious illness commonly associated with childhood. While a vaccine is available to prevent chickenpox, vaccinated individuals can sometimes still contract the disease. This is known as breakthrough chickenpox.
Understanding Breakthrough Chickenpox
Breakthrough chickenpox occurs in individuals who have received the varicella (chickenpox) vaccine. While the varicella vaccine is highly effective, it is not 100% effective, so a small percentage of vaccinated individuals can still develop the disease. Two doses of the vaccine are about 90% to 92% effective at preventing chickenpox. Breakthrough cases typically occur more than 42 days after vaccination.
These breakthrough cases are generally milder than chickenpox in unvaccinated individuals. Symptoms often include fewer skin lesions, typically less than 50, which may be more maculopapular (flat spots) rather than the characteristic fluid-filled blisters. Patients with breakthrough chickenpox usually experience little to no fever and a shorter duration of illness.
How Contagious is it and How it Spreads
Breakthrough chickenpox is contagious, though generally less so than a typical chickenpox infection in unvaccinated individuals. The level of contagiousness is directly related to the number of lesions present on the infected person. Individuals with mild breakthrough varicella, characterized by fewer than 50 lesions, are estimated to be about one-third as contagious as unvaccinated people with chickenpox. However, if a vaccinated person develops 50 or more lesions, they can be just as contagious as an unvaccinated person.
The virus primarily spreads through direct contact with fluid from the blisters. It can also spread through airborne droplets released from coughing or sneezing, even before the rash appears. The incubation period typically ranges from 10 to 21 days, with an average of 14 to 16 days. An individual with breakthrough chickenpox is considered contagious from one to two days before the rash onset until all lesions have crusted over. For vaccinated individuals whose lesions may not crust, contagiousness lasts until no new lesions have appeared for 24 hours.
Who is Most at Risk
Breakthrough chickenpox cases can transmit the virus to others, particularly those who are susceptible. Unvaccinated individuals are at the highest risk of contracting chickenpox from a breakthrough case. This includes young children who are not yet vaccinated and adults who have never had chickenpox or the vaccine.
Immunocompromised individuals are also highly susceptible, regardless of their vaccination status, and face a higher risk of severe complications if they contract the virus. Pregnant individuals are also a concern, as chickenpox during pregnancy can potentially impact the fetus. Newborns whose mothers are not immune are also at increased risk for severe disease.
Steps to Take
If breakthrough chickenpox develops, certain steps can help prevent further spread and manage the illness. Isolation is recommended to minimize transmission, meaning staying home from school or work until all lesions have crusted over. Good hygiene practices, such as frequent handwashing, are also important.
Consulting a healthcare professional for diagnosis and guidance is advisable, especially if vulnerable individuals have been exposed. For symptomatic relief, over-the-counter medications like acetaminophen can help with fever, and oatmeal baths can soothe itching. Vaccination remains the most effective way to prevent severe chickenpox and reduce its transmission within the community.