How Contagious Is The Delta Variant Of COVID-19?

We already knew that the Delta variant is much more contagious than the original strain of COVID-19 first discovered in late 2019. What may be more surprising is that according to a CDC document uploaded by The Washington Post, the Delta variant may be as contagious as chickenpox. Chickenpox is notorious for being highly contagious; before chickenpox vaccines were invented, it was pretty much impossible to avoid getting the disease at some point during childhood (per Johns Hopkins Medicine).

In addition, the Delta variant is more contagious than smallpox, polio, SARS, and the 1918 flu. While vaccinated people remain three times less likely than unvaccinated people to get the Delta variant, vaccinated people with breakthrough infections may be just as likely to spread the virus to others. The Delta variant may also be more likely to cause reinfections, but only in people who had the virus more than six months ago, according to the CDC.

With all of this in mind, it is no surprise that since the arrival of the Delta variant, COVID-19 cases have been spiking in the United States for the first time since late 2020 (per CDC).

The return of mask recommendations followed evidence that vaccinated people can still transmit the virus. "The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones," said CDC Director Rochelle Walensky (per University of Minnesota).

But while breakthrough cases are more common with the Delta variant than other forms of COVID-19, vaccines still greatly reduce a person's risk of getting infected with the virus, and the Pfizer vaccine remains at least 93% effective against hospitalization and death (per CDC). Because of this, higher vaccination rates in the population could reduce the spread of the Delta variant. We already see that much of the spread of the Delta variant is among unvaccinated people (via New York Times).

According to research from Johns Hopkins University, COVID-19 vaccines are considerably less effective for immunocompromised people. There are also other groups of people who are unable to get the vaccine (per Healthline). This is one of the reasons it remains important to take steps to avoid spreading the virus, even if most people have the option to get vaccinated. We also don't want to give the virus an opportunity to mutate to the point it may circumvent our current vaccines (per Business Insider).