A measles outbreak in Ohio has raised concerns about the spread of the disease and how a drop in childhood vaccination rates could lead to new 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 were in unvaccinated children. Hospitalization was required for 34 of those infected.
It is not the only recent measles outbreak in the country.
Minnesota experienced 22 cases in the Twin Cities area last year.
The outbreaks, which are the result of an increase in anti-vaccine sentiment, have raised concerns among health experts about whether lower vaccination rates will lead to a further spread of diseases that vaccines can protect against.
“With all the vaccine-preventable diseases, we always worry if there isn’t enough herd immunity,” said physician Susan Koletar, director of the Ohio State Wexner Medical Center’s Division of Infectious Diseases.
Herd immunity occurs when enough people are immune through vaccination or natural infection to prevent a disease from spreading. Measles is so contagious that immunization rates must be at least 95 percent to eliminate the disease.
The Ohio outbreak began in October 2022, with most cases occurring from mid-November to early December. These community cases are believed to be related to one of four travel-related measles cases, says physician Mysheika W. Roberts, the health commissioner for Columbus.
Although most cases occur in unvaccinated children, six of the children had received their first of two doses of the combined measles, mumps, and rubella (MMR) vaccine. According to the agency’s website, another twenty-four of the children were too young for any dose.
The US was declared measles-free in 2000, but travelers regularly bring infections. People who visit countries where measles is endemic, meaning there is regular population transmission, can return to their home communities and cause a local outbreak.
“The mere fact that individuals who were not vaccinated traveled to a measles endemic country and were then allowed to return to the United States, where they likely caused this outbreak, worries me as a public health professional,” says Roberts.
One of the possible reasons why these measles outbreaks may be occurring is that vaccination rates fell during the pandemic.
The Centers for Disease Control and Prevention (CDC) reports that preschool vaccination rates are high, but coverage for the 2021-2022 school year has dropped to 93 percent compared to 95 percent for the 2019-2020 school year.
The risk of contracting vaccine-preventable diseases is particularly elevated for children in low-income households or those living in rural areas, as vaccination rates for those groups declined by 4 to 5 percent during the pandemic, the CDC said.
That decline in childhood vaccinations stems in part from disruptions during the pandemic, as well as financial and logistical hurdles, the CDC reported. But growing vaccine hesitancy and the anti-vaccination movement have also contributed, and are a major factor behind recent measles outbreaks.
The U.S. saw the highest annual number of measles cases in recent memory in 2019 with 1,274, most of which occurred in eight unimmunized communities, according to the CDC.
“We live in a generation where most of the people who are hesitant about the vaccines have never had one of those diseases,” says Koletar. “And they never experienced any of those illnesses because of widespread immunization practices.”
“I think a lot of parents feel that since they don’t see measles in our community, it’s safe for them not to get their child vaccinated,” says Roberts.
She attributes some of the hesitation about vaccines to the spread of misinformation. An example of this is a debunked theory linking the MMR vaccine to autism. Unfounded concerns fueled by that theory may lead some parents to delay the MMR vaccination until just before their child starts 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. “Without the MMR vaccine, we couldn’t eradicate measles.”
The politicization of vaccines during the COVID-19 pandemic has also led to anti-vaccination attitudes, she says.
“The anti vaxx [and] the hesitant vaccine community has probably grown as a result of this pandemic and has transitioned from the hesitation of COVID-19 to all hesitation against vaccines,” notes Roberts.
Each family can weigh their own personal risk and make decisions that way, said vaccine safety researcher Elyse Kharbanda. Willingness to get vaccinated may increase if transmission is high or if there’s a recent memory of an outbreak, but once that’s gone, vaccine acceptance may decline, she continues.
Amid declining vaccination rates, Koletar is concerned there could be an increase in other vaccine-preventable diseases, such as tetanus, rubella and chickenpox. Rubella can be more difficult to diagnose than measles and can sometimes go undetected, according to Koletar.
People in their late teens and adults who haven’t had or been vaccinated against chickenpox can get very sick if they get chickenpox, she adds. “As a doctor, these are scary times, especially when you have a young pregnant woman who gets chickenpox.”
For now, the situation looks positive in Ohio. The most recent case of measles was discovered on Dec. 24, meaning that if there are no new cases through Feb. 4, the outbreak could be officially declared over.
Looking ahead, Khabanda says there is a need for more research into what interventions could help get more people in vaccine-resistant communities to accept vaccines.
Interventions such as warnings and letters are “effective in promoting vaccination among families who plan to vaccinate their children and who are just busy and forgotten,” Khabanda tells The Hill.
But “these kinds of simple interventions really don’t work with families and communities that are anxious and vaccine resistant,” she says. It takes time and good community relations to understand what beliefs are perpetuating vaccine hesitancy and to gain trust, she adds.