COVID-19: The Worst Birthday Gift?

Are birthday parties more risky for children? As these dates of celebration come around the calendar again, a lot of us are still wondering how to navigate gatherings during the ongoing pandemic. Guidelines, research, and information are comparatively plentiful for large, formal gatherings, but not as much for smaller, informal events.

Last week JAMA published a study that assessed the rates of COVID infection after households experienced birthdays.

What did they do?

Scientists at RAND and Harvard pulled insurance data on 6,535,987 individuals in 2,926,530 households from January 1 to November 8, 2020 to access household birthdates and COVID19 diagnoses. They looked at the entire week of a household birthday AND 2 weeks after were monitored to account for social gatherings occurring on close but non-birthday dates and the chance of symptoms occurring up to 2 weeks after infection. Importantly, they also looked at:

  • Levels of community transmission

  • Number of household members

  • Whether the person celebrating was a child or an adult

  • If the event was a milestone birthday (16th, 18th, 20th, 30th, 40th, 50th, and 60th)

  • The political leanings of a community

  • Rainy weather (which could move an outdoor party indoors)

What did they find?

Households with a birthday had 8.6 more diagnoses per 10,000 individuals compared with households without a birthday.

  • A child’s birthday had an increase of 15.8 per 10,000 COVID19 infections compared to adult birthdays

  • Households in areas of high community transmission had a 31% increase in COVID-19 diagnoses compared to areas with low community transmission

There was no meaningful increase in COVID19 risk if…

  • The event was a milestone birthday (“suggesting that these birthdays did not offer a special reason for people to gather or change the way they gather”)

  • If there was rainy weather (“suggesting that the decision to gather was not associated with this specific element of weather”)

  • The presence of county-level shelter-in-place policies (“suggesting that compliance with these policies for these particular events may be low”)

  • Political leanings in the household’s county (“suggesting that individuals’ decisions on whether and how to gather for birthdays were similar between these areas, despite differences in state policies and political views around social distancing and masking”)


There are always strengths and weaknesses to scientific studies. Never is one study perfect. So, keep in mind that this study:

  • Did not track asymptomatic COVID cases;

  • Did not include households with public health insurance (such as Medicare and Medicaid);

  • That households could have differentially sought out testing after a party;

  • No vaccines were administered yet, which would obviously change the story (at least for 12+).

If we were to take all of these limitations into account it could (or could not) impact the results. Nonetheless, this is a strong analysis and important study given our little ones will not be vaccinated for a while.

Bottom line

Birthdays (and small social gatherings) are risky. Especially among kids and especially in areas with high transmission rates. The quicker we protect our community with vaccines, the quicker we (and more importantly our kids) can celebrate safely.

Love, YLE

P.S. I would like to especially thank Anika for drafting the first iteration of this post. She is an extremely bright high school (!!) student who is interning with me this summer to learn about epidemiology and scientific communication. And she is just killing it!

P.S.S. I originally placed indoor birthday parties as high risk for transmission (see below), and I still agree with this placement.