People are bracing for a wave of event cancellations due to the Delta variant. Vaccine mandates could keep organizers from calling everything off.

• Some organizers are cancelling large events, like the New York Auto Show, as COVID-19 cases surge.
• Some other venues are requiring proof of vaccination upon entry.
• Public health experts said vaccine-only events are safer and provide an incentive to get shots.

As cases and hospitalizations rise due to the Delta variant of COVID-19, organizers called off the New York Auto Show and the New Orleans Jazz Fest.

Cases of COVID-19 have climbed since July after months of steady decline. Florida has become the epicenter for the new wave, in part due to its relatively low vaccination rate.

The Centers for Disease Control and Prevention reinstated its recommendation for both vaccinated and unvaccinated people to wear masks indoors in high-transmission areas due to the rise in cases.

But because a COVID-19 vaccine prevents severe illness from the Delta variant in the vast majority of cases, some experts said requiring vaccines at large events could reduce the risk of attendees becoming infected with COVID-19.

Donald Dumford, an infectious disease specialist at Cleveland Clinic, said large events pose a greater risk due to the spread of the more contagious Delta variant. Though studies suggested vaccinated people do not spread the original strain of COVID-19 as often as unvaccinated people, the same does not hold for the Delta variant.

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Fully vaccinated people have a 50-60% lower risk of infection from the Delta variant, compared to unvaccinated people, according to a new study out of the UK. The study hasn't been reviewed by other scientists. A full vaccine course reduces the risk of hospitalization by 90%.

Despite the effectiveness of vaccines, the federal government has not required all citizens get a COVID-19 vaccine - but individual cities and businesses have. New York City mayor Bill de Blasio announced a requirement to get vaccinated before entering indoor restaurants, gyms, and performance venues. United Airlines, Walmart, and Google all moved to require certain employees get their shots.

Dumford suggests both vaccinated and unvaccinated people wear masks at all large gatherings to keep the virus from spreading. He added requiring vaccines at large gatherings reduces the risk of a breakthrough infection.

"Even though we've seen breakthrough cases, and those people with breakthrough who are vaccinated are just as contagious as the unvaccinated, you are eight times less likely to acquire COVID if you are vaccinated," Dumford explained.

Not only are vaccinated-only events safer, they could encourage more people get shots. Amesh Adalja, a senior scholar and infectious disease specialist at the Johns Hopkins Center for Health Security, said requiring proof of vaccination before attending pre-pandemic-type events could sway unvaccinated people who are on the fence.

"It should be thought of, and promoted, as a value to them individually that allows them to safely resume their pre-pandemic lives," Adalja told WebMD. "I also think that when people can tangibly see how being vaccinated will change their lives for the better, it will motivate them to become vaccinated."