Analysis: What causes breakthrough measles infections among a very small percentage of people.a

What causes breakthrough measles infections? A small number of people who are fully vaccinated may get sick during a large outbreak, doctors say. NBC News

...Infectious diseases doctors are at pains to emphasize that the MMR vaccine is one of the most effective vaccines on the market, but as Rodney Rohde, a professor at Texas State University explains, a small number of people who are fully vaccinated may get sick during a large outbreak.

One dose of the MMR vaccine is 93% effective at preventing measles, with the second dose increasing that to 97%.

“The vaccine is highly effective,” said Rohde. “But it means that after two doses, while 97 out of 100 people will develop strong immunity and be protected if exposed to measles, the remaining three out of 100 could still be vulnerable.”

The latest outbreak has seen claims circulating on social media from people who say they are fully vaccinated and still contracted a breakthrough infection, making them seriously unwell, something Rohde said is “slightly possible.” “They could fall into one of those small percentages that got the full vaccine but just didn’t respond,” he says.

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