Election rallies linked to an increase in COVID-19 hospitalizations

By Dr. Ananya Mandal, MDNov 4 2020

Over 48 million people worldwide have already been infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes Coronavirus Disease-2019 (COVID-19). The infection has claimed over 1.22 million lives around the world. The virus spreads rapidly between humans, and large gatherings facilitate the spread of the infection.

Researchers from Ben-Gurion University, Israel, Harvard Medical School, Boston, and Tel Aviv University, Israel, have studied the correlation between large gatherings and hospitalization risk due to COVID-19. Their study titled, “Association of Mass Gatherings and COVID-19 Hospitalization,” was published as a preprint on the medRxiv* server.

Study: Association of Mass Gatherings and COVID-19 Hospitalization. Image Credit: wellphoto / Shutterstock

*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Background

The SARS-CoV-2 virus was first detected late last year in Wuhan, China, and since then, most nations and organizations prohibited mass gatherings to prevent the spread of person-to-person transmission of the infection. The researchers wrote that by September 2020, some policymakers relaxed norms to allow gatherings to resume. The team wrote that such gatherings were seen in Minnesota, United States, after which there were two cases of hospitalization due to COVID-19 among two participants. They wrote, “It is not known if they were infected in the gathering, and if the rate of hospitalizations changes following mass gatherings.”

This study was conducted to see the association between mass gatherings and the risk of hospitalizations due to COVID-19.

Study design

For this study, the team gathered COVID-19 hospitalization data and categorized them by date and county.

They collected data on mass gatherings seen in the form of outdoor rallies in Beltrami, Minnesota (seen on 18^th September 2020), Marathon, Wisconsin (on 17th September 2020). The total population at risk at these two counties was 182,880, as per the U.S. Census data.

Next, the team assessed the incidence rate of COVID-19 per 100,000 capita and calculated a weekly moving average. This was then compared with the changes in the incidence of new cases from the day of the gathering to three weeks after that. The rates of hospitalizations during that time were also assessed for the two counties.

The rates of infections and hospitalizations were compared with states and counties which did not have a mass gathering rally since April 2020. They tracked the rates of COVID-19 hospitalizations in these regions as well via the COVID-tracking project. These states were “Alabama, Arkansas, Colorado, Connecticut, Georgia, Hawaii, Idaho, Indiana, Kansas, Kentucky, Massachusetts, Maryland, Maine, Mississippi, Montana, North Dakota, Nebraska, New Jersey, New Mexico, New York, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Tennessee, Utah, Washington, and Wyoming,” wrote the researchers.

What was found?

Overall results showed that hospitalization rates rose by 15-fold in the Minnesota gathering county and 12.7-fold in the Wisconsin gathering county compared to non-gathering regions. A state-level increase of 2-fold in Minnesota and 2.3-fold in Wisconsin was seen, and no significant rise was seen in non-gathering states.

Results were summarized as:

In Beltrami

• On the day of the gathering, the hospitalization rate was 0.3/100,000 (95% confidence interval -0.2 to 0.8)
• On Day 21 after the gathering, the hospitalization rate increased to 4.5/100,000 (95% confidence interval 1.5 to 7.6)
• A 15 fold rise was recorded

In Marathon

• On the gathering day, the hospitalization rate was 0.3/100,000 (95% confidence interval 0 to 0.6)
• On Day 21 after the gathering, the hospitalization rate increased to 3.8/100,000 (95% confidence interval 2.5 to 5.1)
• A 12.7 fold rise was recorded

In Minnesota

• On the gathering day, the hospitalization rate was 0.6/100,000 (95% confidence interval 0.5 to 0.7)
• On Day 21 after the gathering, the hospitalization rate increased to 1.2/100,000 (95% confidence interval 1.1 to 1.3)
• A 2 fold rise was recorded

In Wisconsin

• On the gathering day, the hospitalization rate was 0.8/100,000 (95% confidence interval 0.7 to 0.9)
• On Day 21 after the gathering, the hospitalization rate increased to 0.8/100,000 (95% confidence interval 0.7 to 0.9)
• A 2.3 fold rise was recorded

Non-gathering states

• On the comparison day the hospitalization rate was 0.6/100,000 (95% confidence interval 0.4 to 0.8)
• On Day 21, after the comparison, the hospitalization rate was 0.8/100,000 (95% confidence interval 0.5 to 1.1)
• A 1.3 fold rise was recorded, which was not significant

Conclusions and implications

The researchers said that this study and its findings reveal that a significant increase follows mass gatherings in COVID-19 related hospitalizations. They suggest further restrictions on mass gatherings such as “political rallies, large school assemblies, and cultural events.” They suggest preparations by healthcare infrastructures (including the hospitals) near regions where such gatherings are allowed. Social distancing and masks must be worn along with avoidance of such gatherings to reduce the risk of COVID-19 infections and resulting hospitalizations, they conclude.

*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.