New Analysis Reveals a Link

New analysis reveals link between birthdays and spread of COVID-19 during the peak of the pandemic.

According to a new analysis led by researchers from Harvard Medical School and the RAND Corporation, counties with already high COVID-19 infection rates may have fueled the spread of infections during the peak months of the pandemic.

The report, published today (June 21, 2021) in JAMA Internal Medicine, shows that in counties with a high rate of COVID-19, households with recent birthdays were 30 percent more likely to receive a COVID-19 diagnosis. , compared to households without birthdays. The analysis is based on data from health insurance claims.

The researchers point out that they did not include real birthday parties in their analysis. Instead, they used household members’ birth dates as a proxy for social gatherings and in-person festivities.

Nevertheless, the team said, the findings indicate that social gatherings, such as birthday parties, may have contributed to infections during the height of the pandemic.

“These gatherings are an important part of the social fabric that holds families and society as a whole together. However, as we show, in high-risk areas they can also expose households to COVID-19 infections,” said senior author Anupam Jena, the Ruth L. Newhouse Associate Professor of Health Care Policy at HMS.

With increasing vaccination rates and declining infections in many parts of the country, such an analysis may seem outdated in retrospect, but the findings hold important clues for public health officials and individuals if a new wave were to emerge, the scientists said.

“Our results can help inform future measures,” Jena said. “They underline the importance of understanding the types of activities that can exacerbate viral spread during a pandemic and can inform policy and individual decisions based on risk. The findings also quantify the potential risk of coming together with people we know.”

For more than a year beginning in early 2020, many schools in much of the United States were closed for personal learning, large segments of the population worked from home, and many forms of large and formal gatherings were strictly restricted, including sporting events. events, concerts and funerals. Despite these restrictions, aimed at reducing the kinds of social interactions that fuel a contagious outbreak, the country has seen more than 32 million confirmed cases of COVID-19 and nearly 600,000 deaths.

Experts speculate that small and informal gatherings may have played an important role in the spread of the virus, but the degree of risk associated with various types of social activities has been difficult to measure, or even estimate. In the absence of massive contact tracing and widespread diagnostic testing, finding data linking new infections to most types of informal gatherings would be a huge challenge, the researchers said.

To get around those hurdles, Jena and colleagues tried to tease the relationship between social gatherings and COVID-19 by examining whether the infection rate is increasing in households where a member recently had a birthday, as these occasions are often celebrated with some sort of get-together , and dates of birth are embedded in medical records and insurance databases, along with COVID-19 diagnoses.

The researchers analyzed a nationwide sample of nearly 3 million U.S. households with Castlight Health employer insurance. In the first 45 weeks of 2020, the researchers found that in countries with high COVID-19 transmission, households with recent birthdays had an average of 8.6 more cases per 10,000 people than households in the same counties without a birthday.

The magnitude of the risk varied based on the age of the person having a birthday. In households where a child had a birthday, the effect was even greater, with an increase in COVID-19 cases of 15.8 per 10,000 people in the two weeks following a child’s birthday compared to cases in families without a birthday. In households with an adult birthday, the increase was 5.8 extra cases per 10,000. The researchers speculated that households with children’s birthdays may be less likely to cancel birthday plans because of the pandemic, or that social distancing may have been less strictly enforced at children’s birthday parties.

Among households in counties with low COVID-19 prevalence, the study found no increased infection rate in the weeks following birthdays. The researchers also didn’t find that the overall link between birthdays and COVID-19 differed based on the political affiliations of the household’s province, or on other factors, such as whether it rained the week of the birthday — potentially leading to indoor celebrations. whether there was a reception policy in place in the household’s province at the time of the birthday.

“We have only been able to examine one type of event likely to lead to social gatherings, but given the magnitude of the increased risk associated with having a birthday in the household, it is clear that informal gatherings of all kinds played an important role in the spread of COVID-19,” said co-author Christopher Whaley of the RAND Corporation.

Reference: June 21, 2021, JAMA Internal Medicine.
DOI: 10.1001/jamainternmed.2021.2915

Support for the research was provided by grant 1K01AG061274 from the National Institute on Aging.

Disclosures: Whaley reported receiving consultancy fees from Doximity outside of the submitted work. Jena reported receiving personal benefits from Pfizer, Bioverativ, Bristol Myers Squibb, Merck, Janssen, Edwards Lifesciences, Novartis, Amgen, Eli Lilly, Vertex, AstraZeneca, Celgene, Tesaro, Sanofi Aventis, Precision Health Economics and Analysis Group outside of the filed work . No other disclosures were reported.