Does the Chickenpox Vaccine Used in the U.S. Stop Infection and Transmission of Chickenpox?

Aaron Siri | 31 March 2024

Does the chickenpox (varicella) vaccine used in the United States stop infection and transmission of chickenpox?

“Yes” or “No”?

(Answer below. Paywall will be removed in seven days!)

For those hoping for a “Yes!” you finally got one! Yes, the chickenpox vaccine can prevent infection with and transmission of the chickenpox virus, known as varicella. But here is the incredible thing: those vaccinated with the chickenpox vaccine can transmit the virus to others for six weeks after vaccination yet are never excluded from school during this period.

As the FDA-approved package insert for the chickenpox vaccine explains: “transmission of varicella vaccine virus [] resulting in varicella infection including disseminated disease may occur between vaccine recipients (who develop or do not develop a varicella-like rash) and contacts susceptible to varicella including healthy as well as high-risk individuals” and that “[d]ue to concern for transmission of vaccine virus, vaccine recipients should attempt to avoid whenever possible close association with susceptible high-risk individuals for up to six weeks following vaccination” including immunocompromised individuals, pregnant women, and newborn infants of mothers without documented history of varicella.  

However, no child (either recently vaccinated or unvaccinated for chickenpox) needs to be excluded from school to protect these individuals. This is because (i) anyone immunocompromised to the degree that chickenpox could seriously harm them is already not attending school because if the chickenpox virus can seriously harm them, so can around 1,400 other known human pathogens, (ii) an estimated over 98% of women aged 20-49 in the U.S. are immune to chickenpox, and pregnant women are routinely screened so those who aren’t immune can take appropriate measures, and (iii) newborns do not attend school.

This doesn’t even touch on whether risks from chickenpox are more or less than risks from the chickenpox vaccine (stay tuned for a lot more on that later in this Vax Facts series).

Screenshots of the relevant portions of the websites linked above (in case they change):

Screenshot of Varivax insert
Screenshot of CDC study
Screenshot of varicella seroprevalence study
Screenshot CDC prenatal screening guidelines

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