‘A perfect storm’: What’s our protection level against measles amid Chicago outbreak?

Considered to be effectively eliminated across the U.S. in 2000, a measles outbreak in Chicago this month is a wake-up call about how easily things can spiral, experts say.

So, how well protected are Illinoisans against the highly contagious and sometimes deadly respiratory virus?

The measles vaccination rate for K-12 students statewide is estimated at 96.2%, which exceeds recommended levels. But it’s lower for kindergartners at 91.7% as of 2022, the Illinois Department of Public Health reported.

Meanwhile, more than 690 schools fall below the 95% vaccination rate that triggers herd immunity, Illinois State Board of Education records show.

“Vaccines have become the victims to their own success because they’ve been so good, and so effective, that a lot of families have just not seen some of these really scary illnesses,” said Dr. Anita Chandra-Puri, a spokesperson for the American Academy of Pediatrics.

“And that can be a problem because then, they think they don’t have to worry about them. But we do know that this situation can happen, just like it is happening now.”

The Chicago outbreak infected 17 people as of Friday with a majority traced to a migrant shelter. Eleven children age 4 and younger fell sick.

It’s the most infections since 2015 when 17 were reported in Illinois. The epicenter was at a Palatine day care, Cook County Department of Public Health’s Dr. Rachel Rubin recalled.

“It was in the infant room because those children were too young to be vaccinated. One of the kids was infected by an adult and it spread through that entire room,” said Rubin, CCDPH’s senior medical officer.

Babies don’t receive their first measles shot until 12 months; the second dose occurs between ages 4 and 6.

Current data shows Will County with the highest vaccination level for schoolchildren in the region at 97%. That’s followed by suburban Cook County with 96.7%, Lake and McHenry counties at 96.5%, DuPage County at 96.2% and Kane County at 95.6%.

Chicago’s vaccination rate is 93.8%, according to a 2022-2023 Illinois State Board of Education survey.

This week, DuPage and Kane health officials urged residents to ensure they are up to date with the MMR vaccine that protects against measles, mumps and rubella.

Nationally, vaccination rates for measles have declined since the COVID-19 pandemic. Coverage for kindergartners went from 95% in 2019-2020 to 93.1% in 2022-2023, the U.S. Centers for Disease Control and Prevention reported.

That equates to about 250,000 kindergartners across the U.S. who are at risk for measles.

Outbreaks have “been one of the concerns we have had, as immunization rates against measles have fallen,” Puri said.

Although measles was considered eradicated in the U.S., there are international exposures from travelers and people relocating, she explained.

“If you happen to be in contact with measles and you’re unimmunized and get the disease and you bring it into a place with lower immunization coverage rates — it’s a perfect storm.”

Illinois allows exemptions to school vaccination requirements on medical or religious grounds.

Thousands of parents have received religious exemptions statewide, with more than 12,600 reported in the metro region in the 2022-2023 school year.

Concerns were raised after the measles vaccine was falsely linked to autism in the 1990s. It was debunked by the scientific community but that misinformation contributed to vaccine hesitancy.

When she meets parents who are dubious about the vaccine at her Chicago practice, pediatrician Puri works to build trust.

“I talk to them about the risks of the disease. I talk to them about how sick a child can be and the complications of the disease. I talk about the effectiveness of the vaccine and the safety of the vaccine,” she said.

What is ‘herd immunity’

Two doses of the MMR vaccine are 97% effective in preventing the virus and one dose is 93% effective. People who’ve had measles also typically are immune.

When more than 95% of people in a community are vaccinated against measles, most people are protected through herd immunity, according to the CDC.

So, “if you’re vaccinated — you’re protected — and the 5% that are not vaccinated are protected because everybody else is vaccinated around them,” Rubin explained. “That means the virus isn’t circulating because people are not susceptible to it, and it dies down. The 5% that aren’t vaccinated benefit from the rest of us that are vaccinated.”