As the US loses herd immunity, experts believe outbreaks will get worse

As measles makes a rapid resurgence in the United States, childhood vaccination rates have fallen nation-wide for all major immunizations. With these rates continuing to decline, communities find themselves below herd immunity for certain viruses. Experts say these outbreaks will only continue to get worse.

“I think there’s a clear correlation between declining childhood vaccine rates and a significantly increased risk for outbreaks in areas where we have lower rates, and particularly in those areas where communities are below the threshold for herd immunity,” Neil Maniar, the director of the masters of public health program at Northeastern University, said.

Herd immunity allows communities to prevent the spread of a virus by denying it a host. When someone with the virus spreads it through air or by contact, the virus cannot find an un-vaccinated host. Herd immunity thresholds differ for viruses, depending on how contagious they are, but for measles, the threshold is 95%.

According to the U.S. Centers for Disease Control and Prevention, in 2009, 20 states were at herd immunity for the MMR viruses—measles, mumps and rubella—in incoming kindergartners. In 2023, that number had fallen to just 11, with 14 states having under 90% of their community vaccinated.

Jenny Van Amburgh, a clinical professor in Northeastern’s health and public sciences department, warns that, although we’re seeing many of these measles cases in Texas, they can happen anywhere. This is a nation-wide decline in vaccinations.

Despite these vaccinations being essential for public health, counties make it difficult for children to get fully immunized.

“There are a lot of barriers to getting vaccinated,” Lacie Grisley, a school nurse in a low-income neighborhood in Maryland, said. “We have a high immigrant population. Health care’s not even a benefit of the job even if they’re here, working legally.”

A lot of families struggle to have a stable pediatrician to keep track of all the vaccinations, and others simply can’t afford it. Grisley said she’s seen pediatricians take advantage of lower-income families by charging them $25 per vaccine (after a $125 fee to even see the doctor), when the family could get the vaccine for free at the health department.

On top of this, as federal funding gets cut for public health services, programs that provide these free immunizations are at risk.

“The health department in my county is fantastic, but there’s federal money that goes into that, and I don’t know what will happen,” Grisley said.

The removal of these free services will only make getting fully vaccinated harder for families. “If it takes an extra six months to get vaccinated, then you’re losing that percentage for herd immunity,” Grisley said.

Losing herd immunity isn’t the only issue with these lowering rates. Children who aren’t fully vaccinated are particularly susceptible to illness. Their immune systems haven’t fully developed yet, and these diseases can have lifelong side-effects.

Children who get measles have a chance of getting encephalitis—a type of brain inflammation—or becoming blind. This is on top of the potential for death, as three deaths have already been reported due to measles this year. Getting vaccinated helps lower the risk of these larger issues.

“The vaccine ensures that, you know, you have a lower risk of complications,” Maniar said. “That is our best mode of prevention.”

Even children who get sick without major symptoms are missing class, and these outbreaks put stress on the school systems.

“We’ve had some [outbreaks] over the several decades that I’ve been the school nurse,” Billie Jo Kreps, who works as a nurse for young children with IEPs in Maryland, said. “It was tough… I would think that would be a bigger issue than it currently is.”

Despite the fear of outbreaks in schools, which has some parents keeping children home, many experts admitted that vaccine skepticism is rising.

“It’s just much easier for misinformation to spread,” Maniar said. “It is much easier for individuals who have a lot of influence to spread messages that are not necessarily grounded in science or in scientific evidence.”

Grisley admitted that even amongst her families, who are normally not opposed to vaccinations, she’s seen a rise in skepticism for certain vaccines. “I am seeing people more hesitant to flu. There’s a lot of vaccine fatigue.”

For other experts, they believe the issue is that the viruses making a comeback were once eliminated from the U.S. “That’s what makes it challenging from an individual to say well why do I need to be vaccinated if we don’t have any cases? Because once you get it, you can’t get rid of it,” Van Amburgh said.

Pair this skepticism with a CDC that consists of known vaccine skeptics, and the future looks bleak. The CDC continues to change vaccine recommendations, including requiring individuals 65 or older to consult with their doctor before getting a new COVID vaccine, limiting the availability for many people.

“I think these new guidelines are dangerous. I think they are going to lead to fewer people getting the vaccine that they need, and it’s going to lead to more people unnecessarily getting sick and dying from preventable illness,” Maniar said. “We are seeing guidelines that are, and you can quote me on this, completely ridiculous and not based in science.”

Whether due to personal choice or lack of access, not getting vaccinated puts everyone at risk. When a society lacks herd immunity, vulnerable communities are at risk. A child might catch measles and not have a huge reaction. However, they then spread the disease.

“They might have at risk family members who are older and maybe their vaccinations immunity has waned or, you know, all those kinds of things. And, you know, young babies who are under immunized because they’re not able to have as much from that early point. So they’re putting others at risk,” Kreps said.

The only way to fully protect our communities and ourselves is to get vaccinated, but experts fear that with these growing challenges to vaccinations, the nation is setting itself up for worsening outbreak severity.

“We know there will be future pandemics,” Maniar said, “And rather than preparing ourselves for those future pandemics and building up our infrastructure… We are destroying our infrastructure and destroying trust.”