PBS News Hour

JOHN YANG: Good evening.

I'm John Yang.

The growing measles outbreak in the southwestern United States claimed a second life this week.

New Mexico health officials said an unvaccinated adult who did not seek medical care tested positive for the virus after dying.

Measles is a highly contagious disease, but in 2000, health officials said that the widespread administration of the measles vaccine had eliminated it in the United States.

But now the CDC warns that more cases can be expected.

So far this year, more than 220 cases have been reported across 12 states.

Texas, where the outbreak first emerged and where late last month an unvaccinated child died, has the majority of the cases, at least 198since late January.

Jessica Malaty Rivera is an infectious disease epidemiologist at the de Beaumont Foundation.

That's a philanthropy that promotes public health.

Jessica, help us put this in context.

There have been measles outbreaks in recent years.

How is this one different or is it different?

JESSICA MALATY RIVERA, de Beaumont Foundation: Yeah, it is different.

We have had measles outbreaks in previous years.

In 2019, the U.S. nearly lost the elimination status because of 1,300 cases that were reported throughout New York and New Jersey.

And in 2013, there was an outbreak.

When we say outbreak, we refer to cases that involve three or more infections.

In 2024, there were a number of outbreaks.

But two months into 2025, this is our third outbreak and it's growing to be one of the worst.

So it's, you know, when we talk about this, it is unusual for this type of scale, but because of decreasing vaccination rates and vaccine refusal in general, we are seeing emerging cases happen on occasion.

JOHN YANG: Vaccine refusal, is that the main driving force for this outbreak or the previous outbreaks?

JESSICA MALATY RIVERA: Yes.

When we talk about measles herd immunity, which refers to what the vaccination rate that we need to prevent measles outbreaks, it's 95 percent or higher.

When we dip below that percentage, that's when we start to see new cases emerge.

It is the most contagious infectious disease we have, and the MMR vaccine is one of the most effective vaccines.

When we have vaccination rates above 95 percent, that's when we can maintain that elimination status as soon as it starts to dip.

And we've seen that dip below 90 percent in some communities.

But even when it's in the 92, 93 percent range, that is a vulnerability for populations.

JOHN YANG: MMR vaccine 3 measles, mumps, rubella, in that one vaccine.

Talk about the effectiveness and the history of that vaccine.

JESSICA MALATY RIVERA: Yep.

So the MMR vaccine is probably one of the most effective vaccines that we have.

It protects, with one dose, you have 93 percent protection from infection, and with two doses, you protect it up to 98 percent.

The first dose is typically given to children who are between 12 to 15 months, and the second dose is given between the ages of four to six, ideally so that children are fully vaccinated and protected by the time they enter kindergarten.

And it's kindergarten vaccination rates that we're typically looking at when we talk about populations that are either protected or vulnerable.

JOHN YANG: The new Health and Human Services Secretary, Robert F. Kennedy Jr. longtime vaccine skeptic.

When this first outbreak broke out, he said it was not unusual.

He's been suggesting that things like vitamin A and cod liver oil could be remedies.

What effect is that having, do you think.

JESSICA MALATY RIVERA: It's having a pretty significant effect.

It is sowing additional doubt in vaccine confidence.

You know, I think it's important to note that vitamin A cannot prevent measles infection.

Vitamin A is a very specific post infection guidance again offered by the WHO because in some cases measles can deplete a child's vitamin A levels.

And so the dosage of vitamin A is given by a doctor two doses 24 hours apart for the purpose of replenishing that deficiency in vitamin A.

It is not something that should be dosed at home.

It's not prophylaxis or prevention.

The only way to prevent measles infection is through the MMR vaccine.

JOHN YANG: In the first term, of course, President Trump had to deal with COVID.

How well equipped do you think the OR prepared is the second Trump administration for something like this?

JESSICA MALATY RIVERA: This is a really difficult question to answer because it's hard to quantify.

But it doesn't bode well when we are seeing a widespread attack on a lot of our public health institutions.

When I say attack, I the silencing and the kind of removal of essential public health data and public health information.

Right now we're seeing a lot of political fighting when it comes to what CDC and NIH and even FDA can do.

So things are not looking great.

But there are a number of very active public health leaders and organizers who are trying to do the best they can to put out good information and to help create systems of harm reduction and advocacy, kind of the core principles of public health.

JOHN YANG: Epidemiologist Jessica Malaty Rivera, thank you very much.

JESSICA MALATY RIVERA: Thanks, John.