Measles outbreak that sickened 85 children declared over in Ohio

The measles outbreak in central Ohio that left 85 children infected has officially been declared over, Columbus Public Health announced Thursday.

"CPH has received the last pending test result, which was negative for suspected measles cases," the agency tweeted. "We have surpassed 42 days, or two incubation periods, since the last rash onset, which fits the CDC's definition of the end of an outbreak."

According to data from CPH, no cases have been recorded since Dec. 24.

Over the course of the outbreak, which began in November 2022 and was seen across several schools and day cares, 80 of the 85 children infected were unvaccinated.

Four had received at least one dose of the MMR (measles, mumps, rubella) vaccine and one patient had an unknown vaccination status.

An overwhelming majority, or 65%, of cases occurred among children between ages 1 and 5 with children under age 1 being the next most affected group.

In total, 36 children were hospitalized, but none of the sickened children died.

"We did have several children that required intensive care," Kelli Newman, communications director at CPH, told ABC News. "Most cases that were hospitalized were due to dehydration, which is common in young children like that."

Measles is a very contagious disease with the Centers for Disease Control and Prevention saying every individual infected by the virus can spread it to up to 10 close contacts, if they are unprotected including not wearing a mask or not being vaccinated.

Complications from measles can be relatively benign, like rashes, or they can be much more severe, like viral sepsis, pneumonia or brain swelling.

The CDC says anybody who either had measles at some point in their life or who has received two doses of the MMR vaccine is protected against measles.

In the decade before the measles vaccine became available, an estimated 3 to 4 million people were infected every year, 48,000 were hospitalized and between 400 and 500 people died, according to the federal health agency.

One dose of the measles vaccine is 93% effective at preventing infection if exposed to the virus. Two doses are 97% effective.

Children are recommended to receive their first dose between 12 and 15 months old and their second dose between ages 4 and 6.

According to a report from the CDC published in January, during the 2021-22 school year, 88.3% of kindergartners in Ohio had received two doses of the MMR vaccine, less than the national average of 93%.

"I think this is kind of a wake up call for all of us," Newman said. "While this outbreak is behind us, and we're grateful for that, we know that the next outbreak could just be one missed vaccine away."

Newman said CPH spent a great deal on the ground working with community partners and pediatricians to get the MMR vaccine out into the community, as well as educate on the importance of vaccination, in response to the outbreak. This included setting up special vaccine clinics and having pediatricians call parents whose children were behind the schedule to remind them to bring them in for their second shot.

In 2000, measles was declared eradicated from the U.S. thanks to the highly effective vaccination campaign.

However, last November, a joint report from the CDC and the World Health Organization declared measles to be an "imminent threat" around the world.

The report found that in 2021, nearly 40 million children -- a record-high -- missed a dose of the measles vaccine. Specifically, 25 million missed their first dose and 14.7 million missed their second dose.

The authors stated much of the progress that was made in beating back the disease was lost due to the COVID-19 pandemic.

In the U.S., a May 2022 study found one-third of American parents reported a child with a missed vaccination due to barriers imposed by the COVID-19 pandemic.

Newman said that many parents of the unvaccinated children infected with measles had chosen not to have their kids receive the MMR shot due misconceptions that it causes autism, a theory that has been widely debunked across the scientific community.

"Many of these kids were vaccinated for everything, but MMR because there was a lingering misconception that it caused autism," Newman said. "That's what we heard in feedback when we worked with parents during the case investigation and so that was something we had to provide a lot of education and engagement around, and we're continuing to do that." ABC News' Eli Cahan contributed to this report.