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In this video interview, Paul Offit, MD, of Children's Hospital of Philadelphia and a member of FDA's Vaccines and Related Biological Products Advisory Committee, discusses the history of measles and the MMR (measles, mumps, and rubella) vaccine and examines why there are currently several outbreaks of this vaccine-preventable disease in the U.S.

The following is a transcript of his remarks:

Recently, there have been outbreaks of measles in Philadelphia, in Delaware, in New Jersey. In 2022, there was an outbreak in Columbus, Ohio, that resulted in the hospitalization of 85 children, virtually all of whom were unvaccinated.

So, why is this happening? I think to understand that, we need to go back to the beginning.

The first measles vaccine was introduced in 1963. The last, best measles vaccine was introduced in 1968. Now before vaccines were available, every year in the United States there would be 3 to 4 million cases of measles, there would be 48,000 hospitalizations, and 500 deaths. But by 1968, we had an excellent vaccine, a vaccine where one dose would provide 93% immunity protection against measles.

By 1971, we had combined that measles vaccine with two other vaccines: the mumps and rubella vaccines to create the measles, mumps, and rubella (MMR) vaccine. Also, by 1971, the number of states that had school mandates increased from 25 to 40.

The problem was they weren't enforced particularly well. What happened in 1976 is there was an outbreak in Alaska, and that was one of the first examples where the state mandates were enforced, the school vaccine mandates were enforced. So there were 75 children in Alaska who hadn't been vaccinated, and they couldn't get back to school until they were vaccinated. They got vaccinated, and the epidemic subsided. In 1977, there was a massive measles outbreak in Los Angeles County. Again, they enforced a school vaccine mandate, and so 50,000 children could not get back to school until they were vaccinated. And they were vaccinated and came back to school and the epidemic subsided.

By 1981, we had about an 80% decrease in the incidence of measles as compared to before the vaccine, and all 50 states had school vaccine mandates.

But in order to get herd immunity, in order to completely stop the spread of measles, you need to have vaccination rates -- or rates of natural infection and vaccination -- of about 95%, and we weren't there yet. Because it is the most contagious of the vaccine-preventable diseases. It is five times more contagious than COVID, five times more contagious than flu, so you need a very high level of immunity to stop the spread. And we weren't there yet. In the 1980s, we weren't there yet.

As a consequence, between 1989 and 1991, there were about 11,000 hospitalizations, 55,000 cases, and 166 deaths during that 3-year period from measles. And that led to the birth of the second dose. In Philadelphia in 1991 -- and I was there during a few-month period in the winter of 1991 to 1992 -- we had 1,400 cases and nine deaths from measles. So, we weren't there yet.

And that led to the birth of the second dose recommendation in the early 1990s, as you went from 93% effective with one dose to 97% effective with two doses. And with that, we eliminated measles from this country. By the year 2000, we had eliminated the most contagious of the vaccine-preventable diseases -- an amazing accomplishment and really acknowledge just how remarkable that vaccine was and how effective that vaccine was.

But measles has come back for two reasons, the second of which is the most worrisome.

The first was Andrew Wakefield, a British surgeon who published in February of 1998 a paper in The Lancet, which was a respected general medical journal, claiming that the measles, mumps, and rubella vaccine caused autism, for which he offered no proof. All he had were eight children who had recently received the MMR vaccine, who within a month of receiving that vaccine had developed autism.

Now, this was in no way a study, it was just a case series. And very quickly studies were done. There were 18 studies done in seven countries on three different continents looking at children who did or didn't receive the MMR vaccine, showing that there was no difference in the rate of autism between the vaccinated or unvaccinated group. For that reason, and because that paper had certain biological and clinical misrepresentations, that paper was retracted.

But nonetheless, it's hard to retract the fear. It's hard to unring the bell, it's hard to unscare people once you've scared them. So that did sort of push people away from the MMR vaccine.

But I think the bigger reason was COVID, because what happened with COVID was we mandated vaccines in what many considered to be a draconian fashion. You had to be vaccinated or you couldn't go to work or you couldn't go to school or you couldn't go to your favorite restaurant or you couldn't go to a sporting event or you couldn't go to your place of worship. And there was a real rebellion to that. People didn't like that.

We had leaned into this libertarian left hook. And as a consequence, over the last year, there have been hundreds and hundreds of pieces of legislation pushing back against mandates, including school vaccine mandates. What's happened is about 35% of American parents don't think there should be any school vaccine mandates, period.

If you look in November of this year, the CDC published a paper in Morbidity and Mortality Weekly Report showing that for the first time you see a clear drop in kindergarten immunization rates from about 95% to 92%, which puts us below the level of herd immunity necessary for protection against measles.

I think that's what we're up against, now. We're up against pushing back against school mandates. And if we do that, and if we do that successfully and we largely eliminate school vaccine mandates, measles will be the canary in the coal mine. It will be the first virus to come roaring back.

Measles can make you sick, and measles can make you hospitalized, and measles can make you dead. This is not a disease we want to relive.

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