Did kids’ birthday parties help spread COVID-19? Study says yes

Boston — Guests at children’s birthday parties may have come bearing more than gifts during the height of the COVID-19 pandemic, results of a recent study led by researchers from Harvard Medical School and the RAND Corp. show.

The researchers gathered private insurance data from 2.9 million U.S. households through Nov. 8 and looked at birthdays of household members as a proxy for social gatherings and in-person festivities.

In counties with high COVID-19 transmission, households with recent birthdays averaged 8.6 more cases per 10,000 individuals than households without a birthday, according to a Harvard Medical School press release. In households that had a child’s birthday, they had 15.8 more cases, while households that had an adult’s birthday showed 5.8 additional cases per 10,000 than households without a birthday.

The researchers speculate that children’s birthday parties might have been less likely to be canceled during the pandemic or that physical distancing might have been followed less strictly at such parties.

Higher transmission rates weren’t associated with milestone birthdays, local shelter-in-place policies, precipitation or a county’s political leaning.

“These gatherings are an important part of the social fabric that holds together families and society as a whole,” Anupam Jena, senior study author and associate professor of health care policy at Harvard Medical School, said in the release. “However, as we show, in high-risk areas, they can also expose households to COVID-19 infections. (The results) underscore the importance of understanding the types of activities that may worsen viral spread during a pandemic and can inform policy and individual decisions based on risk.”

The study was published online June 21 in the journal JAMA Internal Medicine.