What we know about the Ohio measles outbreak

A measles outbreak in Ohio is raising concerns about the spread of the disease and how a drop in vaccination rates among children could lead to more outbreaks.

Eighty-five cases have been reported in Ohio as of Friday, mostly in Columbus and other parts of Franklin County, according to Columbus Public Health. Most of these cases involved unvaccinated children. Hospitalization was required for 34 of those infected.

It’s not the only recent measles outbreak in the country.

Minnesota recorded 22 cases last year in the Twin Cities area.

The outbreaks, which occur amid a surge in anti-vaccine sentiment, are raising concerns among health experts that lower vaccination rates will lead to the further spread of diseases that can be protected by vaccines.

“With any of the vaccine-preventable diseases, we always worry when there isn’t enough herd immunity,” says Dr. Susan Koletar, director of the Division of Infectious Diseases at Ohio State Wexner Medical Center.

Herd immunity occurs when enough people are immune through vaccination or natural infection to prevent the spread of a disease. Measles is so contagious that immunization rates must be at least 95% to eliminate the disease.

The Ohio outbreak began in October 2022, with most cases occurring between mid-November and early December. These community cases are believed to be linked to one of four travel-related measles cases, says physician Mysheika W. Roberts, who is the Columbus health commissioner.

Although most of the cases were in unvaccinated children, six of the children had received the first of two doses of the combined measles, mumps, and rubella (MMR) vaccine. Twenty-four other children were too young for any doses, according to the agency’s website.

The United States was declared measles-free in 2000, but travelers periodically bring in infections. People who visit countries where measles is endemic, meaning there is regular transmission in the population, can return to their home communities and seed a local outbreak.

“The mere fact that individuals who have not been vaccinated traveled to a measles-endemic country and then were allowed to return to the United States, where they likely instigated this outbreak, concerns me as a public health professional,” Roberts says. .

One potential reason why these measles outbreaks could occur is that vaccination coverage rates have declined during the pandemic.

The Centers for Disease Control and Prevention (CDC) reports that immunization rates among kindergarteners are high, but coverage for the 2021-2022 school year is down to 93 percent compared to 95 percent for the 2019-2020 school year.

The risk of contracting vaccine-preventable diseases has been particularly high for children in low-income households or live in rural areas, as vaccine coverage has declined for those groups by 4 to 5 percent during the pandemic, according to the CDC.

The decline in childhood immunizations stems in part from disruptions during the pandemic, as well as financial and logistical hurdles, the CDC said. But growing vaccine hesitancy and the anti-vaccine movement have also contributed to and are a major factor driving the recent measles outbreaks.

The United States had the highest annual number of measles cases in recent history in 2019 at 1,274, most of which occurred in eight underimmunized communities, according to the CDC.

“We live in a generation where most people who are hesitant about vaccines have never experienced any of these diseases,” Koletar says. “And they’ve never experienced any of these diseases because of widespread immunization practices.”

“I think a lot of parents feel like they don’t see measles in our community, that it was safe for them not to get their child vaccinated,” Roberts says.

He attributes part of the vaccine hesitancy to the circulation of disinformation. A debunked theory linking the MMR vaccine to autism is one example. The unfounded concern driven by this theory may lead some parents to delay getting the MMR vaccination until just before their child enters school, which could mean the child gets their first dose when they are about 4 years old instead of 12 months old.

The MMR vaccine has been around since the 1960s and is very, very effective, Roberts notes. “We couldn’t get rid of measles without the MMR vaccine.”

The politicization of vaccines during the COVID-19 pandemic has also fueled anti-vaccine attitudes, he says.

“The anti-vaxxs [and] the vaccine hesitancy community has likely grown as a result of this pandemic and has expanded from COVID-19 hesitancy to full vaccine hesitancy,” Roberts notes.

Each family could weigh their personal risk and make decisions that way, says vaccine safety researcher Elyse Kharbanda. Willingness to get vaccinated may increase when transmission is high or there is a recent memory of an outbreak, but once that goes away, vaccine acceptance may decline, he continues.

Amid declining vaccination rates, Koletar is concerned there could be an increase in other vaccine-preventable diseases, such as tetanus, rubella and chicken pox. Rubella can be more difficult to diagnose than measles and can sometimes go unnoticed, according to Koletar.

People in their late teens and adults who haven’t had chickenpox or been vaccinated against it can get really sick if they get chickenpox, he adds. “As a doctor, those are scary times, particularly if you have a young pregnant woman who has chickenpox.”

For now, the situation looks positive in Ohio. The most recent measles case was detected on December 24, which means that if there are no new cases until February 4, the outbreak could be declared officially over.

Looking ahead, there is a need for more research into what interventions would help get more people in vaccine-resistant communities to accept vaccines, according to Kharbanda.

Interventions such as notices and letters are “effective in promoting vaccination to families who plan to vaccinate their children and have just gotten busy and forgotten about it,” Kharbanda tells The Hill.

But “those kinds of simple interventions really don’t work with families and communities that are fearful and resistant to vaccines,” she says. It takes time and good relationships with communities to figure out what beliefs are perpetuating vaccine hesitancy and gain trust, she adds.

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