UNC Health Talk

The Delta Variant: Answers to Your Questions

The rapid spread of the highly contagious COVID-19 delta variant across the United States has health officials urging anyone not yet vaccinated to get a COVID-19 vaccine immediately.

“If you’re waiting for some magical moment to get vaccinated, this is it,” says UNC Health infectious diseases specialist David A. Wohl, MD. “If you’re not vaccinated, now’s the time to get vaccinated to protect yourself from this more infectious and probably more dangerous virus.”

We asked Dr. Wohl to answer common questions about the delta variant.

Why are public health officials worried about this variant?

Viruses are constantly changing, and new versions—called variants—often arise. COVID-19 is no different. Variants identified in the United Kingdom, South Africa, Brazil and India have emerged and are more contagious than the original coronavirus strain. Still, the three COVID-19 vaccines available in the United States have worked extremely well against them in preventing severe disease and hospitalizations.

The delta variant is especially contagious. It was first detected in India and led to a surge in COVID-19 hospitalizations and deaths across the world. It is the dominant strain of the virus in the United Kingdom and now accounts for half of the COVID-19 cases in the United States.

“The delta variant is more contagious, more spreadable, which makes it very dangerous because it’s more likely to find the people who are not vaccinated,” Dr. Wohl says. “As long as a relatively high portion of the population remains unvaccinated, the virus will continue to mutate to become more contagious.”

Do the vaccines work against the delta variant?

Research suggests the vaccines are effective against the delta variant, especially in preventing severe infections and death.

“Remember, vaccines aren’t meant to completely prevent infection or even mild cases. The goal of any vaccine is to keep you from getting very sick and needing to go to the hospital or dying if the virus enters your body,” Dr. Wohl says. “Based on the clinical research, the vaccines appear to do that.”

Recent studies looking at how well the antibodies of vaccinated people fight the delta variant suggest that all three vaccines available in the United States will protect against this virus. Also, a report from Public Health England found two doses of the Pfizer vaccine to be 96 percent effective against hospitalization for the delta variant in the United Kingdom, where nearly all COVID-19 cases are caused by the delta variant. That means almost all those people hospitalized with COVID-19 there are not vaccinated.

“Most breakthrough infections among those who are fully vaccinated tend to be mild or to occur without symptoms,” Dr. Wohl adds.

If I am fully vaccinated, can I still transmit the delta variant to others?

Healthcare officials aren’t sure yet whether a vaccinated carrier of COVID-19 can spread the virus to those who are not vaccinated, including children under age 12.

“Those who have been vaccinated almost certainly would have less virus in their system and therefore are probably less likely to transmit it to others,” Dr. Wohl says. “The duration that person is infectious is also likely shorter if they are vaccinated.”

It’s important to get both doses of the two-dose COVID-19 vaccines made by Pfizer and Moderna. Another report from Public Health England found that a single dose of the Pfizer vaccine was about 33 percent effective against the delta variant, while the full two-dose regimen was nearly 90 percent effective. People are not considered fully immunized until two weeks after the second dose.

“There’s no downside to vaccinating more people. The more people we vaccinate, the less rounds of replication, the less transmission and the less opportunity for a variant to spread and become dominant,” Dr. Wohl says.

Should people who are vaccinated start masking again?

The Centers for Disease Control and Prevention has not changed its guidelines about masking for those who are fully vaccinated. Its guidance says that fully vaccinated people do not need to wear masks. Dr. Wohl takes a more cautious approach; he says that because of the higher transmissibility of the delta variant, it’s a good idea for even fully vaccinated people to wear masks indoors when around people who might not be vaccinated.

“I have never changed my behavior, and I’m fully vaccinated,” Dr. Wohl said. “If I’m indoors around other people who could be unvaccinated, I wear a mask. With delta spreading, that’s the way we should be.”


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