February 9, 2022

The COVID-19 vaccine provides powerful protection against infection for children ages 5 to 11, a new study by Multnomah County epidemiologists found.

The study, examining vaccine effectiveness against the Omicron variant, looked at 750 children who contracted COVID-19 and 750 who tested negative during the peak of the Omicron surge, between Dec. 26, 2021 and Jan. 12, 2022.

The study found that fully vaccinated children (2 doses) were 73% less likely to be infected, compared to unvaccinated children. Partially-vaccinated children (1 dose) were 50% less likely to be infected.

Lucas Alcantara Barrios, 6, gets his first COVID-19 vaccine from his aunt, who works at the Multnomah County Health Department

No children in the study were hospitalized with COVID-19, regardless of immunization status.

County epidemiologist Russell Barlow, who was part of the COVID-19 epidemiology team that conducted the study, said the findings support other research showing pediatric immunizations can play a big role in reducing rates of community transmission and preventing children from getting ill. 

“Not only does this mean those vaccinated kids will be protected, but they’re also less likely to spread infection to vulnerable people in their homes or communities,” he said. “The benefits of this include limited school closures, fewer days of school missed because of isolation and quarantine, reduced COVID-19 spread among vulnerable household contacts, and reduced healthcare use.”

About half of kids ages 5 to 11 in Multnomah County are still unvaccinated—and health officials see an opportunity to reach those families who haven’t yet decided to have their children vaccinated.

Despite a series of surge in COVID-19 cases, Multnomah County Public Health has invested in epidemiological research and data quality throughout the pandemic so local officials can monitor disease trends and adjust its public health response.

Communicable Disease Manager Lisa Ferguson, who has overseen the COVID-19 case investigation and research since the pandemic began, said such research gives families the information they need to  feel confident about choosing to get their kids vaccinated. 

“There are a lot of parents who aren’t sure if they should get their kids vaccinated and we felt it was important to provide factual information to help parents make those decisions,” Ferguson said. 

“Right now we’re figuring out how to pull back on restrictions and mandates without risking new surges in cases,and vaccinations give us a long-term protective measure that can allow us to pull back on some of these restrictions,” she said. “So it’s a priority for us to know whether the vaccines we’re asking people to get are effective against the virus.”

The Multnomah County study did not examine pediatric vaccine safety but early analysis of national data is very reassuring.  It shows that children experience the same minor side effects as adults, such as arm tenderness and fever. But that children ages 5-11 are much less likely to experience myocarditis compared to the rare and usually temporary side effect sometimes seen in older teens and young adults.

In an analysis of about 8 million doses administered to children nationally between Nov. 3 and Dec. 19, 2021, serious adverse events were rarely reported. Of about 100 "serious" adverse events, about 30% reported fever and 20% reported vomiting.

The most frequently reported reactions after a first or second dose of the vaccine were pain at the  injection site, fatigue, and headache. Fever was more frequently reported after the second dose.