In a finding that could help guide the response to the coronavirus pandemic, new research shows that a measles outbreak that struck New York City last year could have been much worse if the city had not launched a vaccine campaign.
The measles outbreak -- the largest in the United States in nearly three decades -- ultimately sickened 649 people. Most were children in a Brooklyn Orthodox Jewish community.
It all began fall of 2018 when an unvaccinated child returned home from a trip to Israel infected with the measles virus. Low vaccination rates in the local Orthodox community allowed the infection to spread.
City officials responded by declaring a public health emergency in April 2019, which included mandatory measles-mumps-rubella (MMR) vaccinations in the affected zip codes.
Had those efforts not taken place, the new study estimates, the outbreak would have been at least 10 times worse.
Anywhere from 6,500 to 8,100 people would have contracted the virus -- primarily babies and preschoolers, according to study author Wan Yang.
"This is a highly infectious disease," said Yang, an assistant professor at Columbia University Mailman School of Public Health in New York City.
Her analysis showed that delayed MMR vaccination among young children was, not surprisingly, the primary driver behind the outbreak. But the spread was likely accelerated by "measles parties" -- where parents deliberately brought young children together to expose them to the disease, with the idea of giving them "natural" immunity.
Parents today, Yang noted, generally have little idea of what measles is like, thanks to vaccinations. So they may not understand how serious the disease can be, she said.
According to the U.S. Centers for Disease Control and Prevention, about 20% of Americans who contract measles end up in the hospital, while 1 to 3 in every 1,000 die.
The New York outbreak was the largest the nation has seen in decades, but smaller ones have been occurring for years. They happen, the CDC says, when a traveler brings the virus into the United States and it then spreads among pockets of unvaccinated people -- often fostered by "anti-vaxxer" sentiment among some parents.
After New York set its vaccination campaign into motion, more than 32,000 children and teenagers received the MMR vaccine by July 2019, according to Yang. In September, the outbreak was declared over.
However, concerns about a future outbreak are high: Since the new coronavirus hit U.S. shores, routine childhood vaccinations have dropped -- as parents avoid taking their children to the doctor's office.
In New York City, Yang said, MMR vaccination rates have reportedly dropped by 63%. Nationwide, a CDC study found that routine childhood vaccinations plummeted starting in late March.
And that's troubling, said Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia.
"We have an under-vaccinated population of children who are vulnerable to diseases like measles and whooping cough," said Offit, who was not involved in the study.
For now, he noted, social-distancing measures and mask-wearing are affording some protection.
But, Offit stressed, the last thing anyone needs going into fall and winter is a large group of children vulnerable to preventable diseases.
"Expect this winter to be bad," he said. "You'll have the seasonal flu and SARS-CoV-2 circulating. If we also have measles, health care systems could be overwhelmed."
His advice to parents: "Get your child vaccinated now."
Yang agreed. "We need to be as prepared as possible when winter comes," she said. "Talk to your child's doctor and get caught up on vaccinations."
For her study, Yang created a computer model to simulate the transmission of measles through the Orthodox community, based on New York City data. The findings, published May 27 in the journal Science Advances, indicate that delayed MMR vaccinations among 1- to 4-year-olds gave the infection a foothold.
Then, increased contact among preschoolers -- likely at measles parties -- fanned the flames.
The results also highlight a broader issue about the effectiveness of vaccines: As long as people refuse to get them, the population remains vulnerable. And recent surveys suggest that if a COVID-19 vaccine becomes available, many Americans might say no.
Offit said he understands the wariness, given the rush to develop a vaccine. "It's reasonable to be hesitant about something that's new that's going into your body," he said.
But practically speaking, Offit added, many people won't be making that call right away. Any COVID-19 vaccine will not be universally available all at once. It will likely be distributed in a "tiered" fashion, with the first doses offered to people at higher risk of severe disease.
Children, he noted, will not be at the top of that list.
The U.S. Centers for Disease Control and Prevention has more on childhood vaccinations.