During the briefing, several committee members stressed that vaccination side-effects are far less risky than the harm that could be caused by the diseases they prevent.
"People forget what these diseases are like," Wright-Clayton added, giving examples of cases of tetanus and Haemophilus influenza she treated as a resident physician. "They are very bad diseases."
However, the committee determined that there is convincing evidence to support a causal relationship (the first category) between the varicella zoster vaccine to four specific adverse events, all due to infection from the vaccine virus strain, and placed this vaccine in the first category.
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The adverse events that there is convincing evidence are linked to these vaccines include disseminated varicella infection, a widespread chickenpox rash shortly after vaccination, varicella infection with subsequent infection resulting in pneumonia, meningitis or hepatitis in people with immunodeficiencies, vaccine strain viral reactivation – manifested as the appearance of chickenpox rash months to years after vaccination – and vaccine strain viral reactivation with subsequent infection resulting in meningitis or encephalitis, or inflammation of the brain.
Also in the first category is the MMR vaccine, which the committee linked to a disease called "measles inclusion body encephalitis," in which rare cases affect people whose immune systems are compromised usually within a year of acute measles infection or vaccination.
Six types of vaccines, including MMR, varicella zoster, influenza, hepatitis B, meningococcal and tetanus, were linked to anaphylaxis.