One Unvaccinated Teacher Infected 26 People With COVID-19—Including 18 Kids


As kids, teachers, and school staff head back to classrooms, a new COVID-19 outbreak study from the Centers for Disease Control and Prevention (CDC) underscores just how crucial it is for those who can get vaccinated to get the shots—especially in settings where there are many others still too young to get vaccinated. In the study, all it took was one unvaccinated teacher for the highly transmissible delta coronavirus variant to infect 26 people, including half of the teacher's students.

For the study, researchers investigated a recent COVID-19 outbreak in a Marin County, California, elementary school classroom. They identified a total of 27 confirmed COVID-19 cases occurring between May 23 and June 1, 2021. Additionally, the researchers performed genetic sequencing tests on samples from 18 cases—and all of them turned out to be caused by the delta variant.

The investigators traced the outbreak back to one unvaccinated teacher, who was one of only two teachers at the school who had not gotten the vaccine. The teacher developed symptoms on May 19 but continued to work for another two days before getting tested for COVID-19 on May 21, the report explains. Despite the school's indoor mask requirement, the teacher reportedly took their mask off to read out loud to students.

Of the teacher's 24 students, all of whom were too young to be vaccinated, 12 (50%) became infected. And eight out of 10 of those who sat in the first two rows, which were closer to the teacher's desk, developed the infection. The cases included the 12 students in the teacher's class as well as six students (also too young for the vaccines) in another grade and eight people who were parents or siblings of the infected students. The outbreak included three people who were fully vaccinated, but no one in the outbreak required hospitalization or died. Without such widespread vaccination in the community (72% of those eligible in the surrounding city were vaccinated at the time of the outbreak), the researchers suggest the virus may have spread even further.

That said, the researchers note that the spread of the outbreak into the surrounding community may have been even more widespread than their findings indicate. That's because testing for parents and siblings was self-directed, so some people who may have had the virus (particularly those who did not develop symptoms) may not have undergone that testing. The researchers also say that “challenges in testing acceptance among possible contacts from outside the school led to difficulty in characterizing the outbreak’s actual spread into the community.” In fact, they later identified five additional cases in the community that seemed highly likely to be related to this outbreak, suggesting that other cases went undetected.

The findings are a reminder that those who aren't (or can't yet be) vaccinated against COVID-19 are the most vulnerable. And, while making in-person learning possible is a top priority for many parents and schools, it can only be accomplished safely if certain requirements (such as masks) are met—and those safety requirements are really only helpful if people actually follow them. 

As the researchers make clear, vaccines are a crucial part of our public health response to the pandemic, but they can't do everything. In addition to using the vaccines for those who are eligible, we need to continue to rely on “strict adherence” to tools such as masks, social distancing, improved ventilation in indoor spaces, and regular COVID-19 testing to keep people safe—especially those who can't yet get the shots

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