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In the days following March 19, when Gov. Gavin Newsom ordered Californians to shelter in place, a pediatrician in Orange County noticed an alarming trend — a  sharp drop in the number of children coming in for routine vaccinations.

“There’s been a tremendous decline,” said Dr. Eric Ball of Southern Orange County Pediatrics in Ladera Ranch. “In late March and April, we were probably seeing only 30 to 40 percent of our normal patients, and our no-show and cancellation rates were extremely high.” 

Ball was not surprised, since people were told to stay home. But now it has become clear that parents and their children throughout the nation are staying away from their pediatricians during the pandemic: Vaccinations for measles and other diseases have declined dramatically across the United States.

Vaccine doses ordered by doctors in a federal program decreased by about 2.5 million between mid-March, when the national emergency was declared, and mid-April compared with the same period in 2019, according to the Centers for Disease Control and Prevention.

The number of measles vaccinations given to children dropped by 74%, from an average of 5,000 per week before mid-March to 1,300 per week the following month, according to the CDC.

In California, childhood vaccinations have declined 40% from the previous April, according to the state Department of Public Health. Vaccines fell for all age groups, but most notably for children younger than six, according to data from the California Immunization Registry. 

Pediatricians and school nurses worry that the decline in fully vaccinated children comes as California schools are preparing to reopen, perhaps as early as July. This could lead to outbreaks of measles, whooping cough and other serious infectious diseases this year.

California’s strict school vaccination laws require all students in kindergarten through twelfth grade to be fully vaccinated. No exemptions are allowed for personal beliefs.

But the state’s newest vaccine law is not yet being fully implemented. Enacted last year, the law aims to detect fraudulent medical exemptions, but it does not take full effect until January 2021, leaving children in communities with a large number of exemptions even more vulnerable in a time where many parents are afraid to set foot in a doctor’s office.  

“Outbreaks don’t happen across the entire state,” said Sen. Richard Pan, a Democrat from Sacramento and a pediatrician who authored the law and co-authored a 2015 law that banned personal belief exemptions from vaccines.

At Orange County’s Journey School, a public charter school in Aliso Viejo, 33% of students receive medical exemptions from vaccinations, according to state data. At the MUSE School, a private school in Calabasas, the rate is about 50%, and at Yuba River Charter in Grass Valley, it is 64%, the highest in the state, according to a 2019 analysis by the Los Angeles Times.

Pan estimates that less than 1% of children would have a legitimate medical reason to be exempt from vaccinations. 

“These communities are dangerous,” he said. With fewer parents vaccinating during the pandemic, the possibility of an outbreak of measles or other diseases occurring in these schools can only rise, he said.

‘Distinct possibility’ of a measles outbreak

Dr. Arthur Reingold, an epidemiologist at the University of California, Berkeley’s School of Public Health, considers an outbreak in an under-vaccinated community “a distinct possibility.” And although he acknowledges that the spread of measles might be lessened by the current travel restrictions, he points out that as schools reopen, these restrictions will start to lift. 

“If someone travels to an area with measles,” he said, “then you have a raging epidemic of measles.” 

California has a history of such outbreaks. In April 2014, an outbreak linked to Disneyland infected 131 people with measles, prompting Pan and Sen. Ben Allen, a Democrat from Santa Monica, to propose the ban on personal belief exemptions. 

California’s measles vaccination rate is now just below 95%, which is the rate that experts say is protective from the disease. 

Pertussis, commonly called whooping cough, also poses a danger to children, said Dr. Yasuko Fukuda, a pediatrician at Pacific Pediatrics in San Francisco. Even vaccinated children frequently get whooping cough — between 10,000 and 40,000 U.S. children are infected each year, according to the CDC. Vaccines greatly reduce both the risk of developing the disease and its severity.

Pertussis is a cyclical disease – outbreaks tend to worsen every three to five years. So with California’s last large pertussis outbreak in 2014, Fukuda worries that this year could be a bad one for the disease since more children aren’t vaccinated.

“Reminding parents of the vital need to protect their children against serious vaccine-preventable diseases, even as the COVID-19 pandemic continues, is critical,” the CDC report says. 

Like most doctor’s offices in California, Ball said his office is taking extensive precautions to limit patients’ exposure to the coronavirus — separating sick and well patients, checking the temperature of all children and families and even giving vaccinations in the office parking lot. 

Shirley Hendrix, who lives in San Marcos, had been hesitant to take her two sons, who are 22 months and eight years old, to the doctor’s office for routine checkups during the pandemic. But when she went in, she discovered the office had taken extreme precautions to reduce the risk of spreading the coronavirus. Staff met her and her son at the door with hand sanitizer, kept them out of the waiting area and limited physical contact.

Although her son did not need any vaccinations, she said that she intends to keep both her children up-to-date. But, she said, that’s not true of everyone in her community. “I know there’s a lot of people who don’t vaccinate their kids,” she said.

Corin Weaver, a San Diego resident, said that she would vaccinate her 5-year-old child, who starts kindergarten in September if the school requires it this fall. But she opposes vaccines, despite their well-established safety, because she fears they have health effects. “If I could wait until next spring or summer, I will,” she said. 

Pamela Kahn, a registered nurse and President of the California School Nurses Organization, is concerned that some schools will allow parents time to get their children caught up on vaccinations, leaving children vulnerable in the interim. 

Crucial parts of the law enacted last year have yet to take effect. Under the law, all medical exemptions must be submitted to the state beginning January 2021. Doctors then will be subject to scrutiny from state officials.

Until then, Kahn said, schools with low vaccination rates will continue to be vulnerable to outbreaks. 

“There is a level of herd immunity that needs to be reached,” said Kahn, referring to the percentage of kids who need to be vaccinated to ensure protection from a disease. “We’re very concerned about this.” 

The California health department warned that the decline in vaccinations “is concerning now during the pandemic, and will be more concerning once distancing measures are relaxed and there are more social interactions and travel that can spread disease.” 

Social distancing won’t stop measles

Despite what some parents might think, social distancing measures at schools to prevent the spread of the coronavirus won’t eliminate the risk of other infectious disease outbreaks, doctors said. That’s because other diseases can be even more contagious than the coronavirus. A person infected with the coronavirus usually infects four other people, said Dr. James Cherry, a pediatrician and infectious disease specialist at UCLA. But a person with measles will infect closer to 15. Similarly, someone with pertussis usually infects 12 to 15 people, according to the CDC

Doctors also are concerned about the flu, since children are not required to get flu vaccinations. Ball said that thousands of people are hospitalized with the flu each year, and that a bad season could overwhelm hospitals already pushed to their limits by the pandemic. 

Dr. Kenneth Saul, a pediatrician at Rolling Oaks Pediatrics in Thousand Oaks, also worries about daycare centers, which bring together large numbers of infants.

Ball is optimistic that most parents will vaccinate their children before school starts. He hopes that local and state officials will keep drawing attention to the issue. 

“We’re going to try to keep kids apart,” Ball says. “But try to tell a group of 20 five-year-olds to not touch each other. It’s still going to happen.”

This article was updated on June 8 to remove the erroneous assertion that children in daycare centers are not required to be vaccinated.

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Rebecca is an editorial intern at CalMatters helping to cover science, health, and coronavirus stories. She is a current graduate student in New York University's science, health, and environmental reporting...