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Barbara Loe Fisher on Whether Vaccinated People Can Infect Unvaccinated People

Public health officials say that unvaccinated children pose a big danger to those around them and even threaten the health of fully vaccinated children and adults because vaccines can fail to prevent infection in vaccinated persons. Today, the most common argument used to justify ‘no exceptions’ mandatory vaccination laws is that unvaccinated people pose a serious health threat to others who “cannot be vaccinated,” such as the immune-compromised.

Some parents of unvaccinated children are asking the opposite question: Could my unvaccinated or immune compromised child get sick from coming in contact with a recently vaccinated person? When it comes to live virus vaccines, the short answer is: Yes.

During a viral infection, live virus is shed in the body fluids of those who are infected for varying amounts of time and can be transmitted to others. Vaccine strain live virus is also shed for varying amounts of time in the body fluids of vaccinated people and can be transmitted to others.

Although public health officials maintain that live attenuated virus vaccines rarely cause complications in the vaccinated person and that vaccine strain viral shedding rarely causes disease in close contacts of the recently vaccinated, it is important to be aware that vaccine strain live virus infection can sometimes cause serious complications in vaccinated persons and vaccine strain live viruses can be shed and transmitted to others with serious or even fatal consequences.

— Barbara Loe Fisher, co-founder and president of the National Vaccine Information Center (NVIC)



Fisher BF. The Emerging Risks of Live Virus and Virus Vectored Vaccines. The Vaccine Reaction Jan. 14, 2016.

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