Get the measles vaccine, and you won’t get the measles—or give it to anyone else. Right? Well, not always.
A person fully vaccinated against measles has contracted the disease and passed it on to others. The startling case study contradicts received wisdom about the vaccine and suggests that a recent swell of measles outbreaks in developed nations could mean more illnesses even among the vaccinated.
[I]f a fully vaccinated person does become infected—a rare situation known as “vaccine failure”—they weren’t thought to be contagious.
That’s why a fully vaccinated 22-year-old theater employee in New York City who developed the measles in 2011 was released without hospitalization or quarantine. But like Typhoid Mary, this patient turned out to be unwittingly contagious. Ultimately, she transmitted the measles to four other people…
[T]wo of the secondary patients had been fully vaccinated.
By analyzing her blood, the researchers found that Measles Mary mounted an IgM defense, as if she had never been vaccinated.
Her blood also contained a potent arsenal of IgG antibodies, but a closer look revealed that none of these IgG antibodies were actually capable of neutralizing the measles virus.
Although public health officials have assumed that measles immunity lasts forever, the case of Measles Mary highlights the reality that “the actual duration [of immunity] following infection or vaccination is unclear…”