Regular childhood vaccinations dipped during COVID, opening a door for measles outbreaks

Childhood vaccination rates remained low for months after last year’s lockdowns, especially among teenagers, raising the specter of measles outbreaks as schools continue to reopen, according to new research published in Pediatrics.

“The number of vaccines given to kids dropped precipitously right after the state of emergency was declared,” says Bradley Ackerson, a pediatric infectious disease researcher and lead author on the paper. “It was understandable. People were afraid to come into the office.”

There was some evidence, particularly from a study in New York, that by the summer vaccination rates for diseases like chickenpox and measles had picked back up, at least in children under two. But that same study suggested that older kids were lagging behind.

To get the full picture, the researchers examined the percentage of kids in the Kaiser Permanente Southern California health system who were completely vaccinated at specific age benchmarks set by the CDC.

During California’s lockdown, the study found, the number of vaccines going to under-twos dropped by only about 25 percent, but by more than 80 percent among older children. As the state began reopening, the number of vaccines going to the younger group recovered close to pre-pandemic levels, while the older group continued to get fewer shots.

But even with those recoveries, the population as a whole remained undervaccinated. “When we looked at three-, five-, and seven-month milestones, they did improve eventually, but not back to baseline,” Ackerson says. “In older kids, vaccination coverage is actually declining.”

The persistent decline is likely because the kids who missed their shots during lockdown haven’t fully caught up. “In order to get kids up to date, we need to actually exceed previous years vaccination rates,” Ackerson explains.

Another national study of vaccine providers, published in March, pointed out a number of factors that may be creating obstacles to vaccinations. Reduced in-person visits were the biggest concerns, but providers also pointed to lost transportation options and financial strain, including lost health insurance through employers. The federal government provides programs to give vaccines at no cost, but as with COVID vaccines, many people may not know that the shots are free.

Nationally, the CDC and American Academy of Pediatrics urged providers to prioritize vaccines for children under two, a strategy that Ackerson says appears to have worked. During the lockdown, those children were prioritized for the limited number of appointments the healthcare system offered. As the pandemic rolled on, the system opened vaccine-only clinics for parents who were worried about the infection risk of visiting a doctor’s office.

California left its school-based requirements in place, even as classes happened online. “We saw an uptick in 4-5 year olds coming in when the state announced that they would be maintaining the requirement for kids enrolling in kindergarten,” Ackerson says. “That was a big help.”

Still, even among young children, there are worrying signs. The study looked at measles vaccinations specifically, because the disease is the most likely to cause outbreaks in the absence of near-universal immunity.

“We saw the [measles] vaccination coverage for 16 month kids declining as time went on,” Ackerson says. “That means that all those kids, from 16 months to kindergarten, those are all kids that are undervaccinated.” When international travel resumes, and those kids return to daycares in coming months, measles outbreaks could become a real threat.

The study also found a racial disparity in the vaccination rate recovery. Although the stay-at-home orders hit all racial and ethnic groups similarly, Black children were much further behind by the summer.

That has the potential to undo decades of work on vaccine equality achieved before the pandemic: by the mid-2000s, universal vaccine programs and targeted outreach had largely eliminated childhood vaccine disparities. But the economic and health impacts of the COVID pandemic have fallen hardest on Black Americans, so it’s likely that they also disproportionately face transportation and financial barriers.

However, it’s hard to tease out specific barriers in the recent paper. The healthcare system in the study is integrated with an insurance company, and Ackerson—who sees patients in addition to doing research—says that providers reached out to parents who might have lost insurance with information about no-cost vaccinations. That means he suspects that in this study, the drop off isn’t likely to be about losing insurance. And he argues that because the system has a network of clinics distributed across neighborhoods, transportation is less likely to be an issue. (However, people who are public transit-dependent, and likely faced larger transit barriers during the pandemic, are disproportionately Black.)

There are likely larger declines in vaccinations outside the Kaiser Permanente system, Ackerson says. “We know that there’s a lot of settings with underinsured kids where the coverage is even lower.”

The good news, he says, is that existing programs have gone a long way towards addressing the problem. Doctors need to be diligent in telling parents about vaccine-only clinics during telemedicine visits. But teenagers and older kids are somewhat easier to vaccinate than infants, because they can visit drive-through clinics. Says Ackerson, “We were successful with three- to 18-month-olds, so we can be equally successful with the older kids.”