Viruses constantly change through mutation, and new variants of viruses are expected to occur. Multiple variants of the virus that causes COVID-19 have been documented, including a highly transmittable form of COVID-19-Delta variant.

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The Delta variant, which was first seen in December 2020 in India, is spreading globally. It's more contagious than the previous strains that have been detected in the U.S. It's also causing more severe illness. Dr. Melanie Swift, co-chair of Mayo Clinic's COVID-19 Vaccine Allocation and Distribution Work Group, says now is the time to get vaccinated for COVID-19. "We really need to take advantage of this time right now, when we have the vaccines that are freely available for everyone to get vaccinated so that we can stop the spread of the Delta variant, but also so we can prevent the development of new variants," says Dr. Swift. The Mayo Clinic News Network sat down with Dr. Swift, and she answered these questions about the Delta variant:

Given the spread of the Delta variant, why is vaccination for COVID-19 urgent now?

The situation with the Delta variant can't really be overstated at this point. We are really at a pivotal moment in the pandemic right now. We were on the downtrend in the U.S., with increasing vaccination rates and decreasing cases. And what has happened is that we've gone from having our first case of the Delta variant in the U.S. in March to it now being the vast majority of cases that have been sequenced. 

The Delta variant is more contagious than the previous strains that we've had in the U.S. But it's also causing more severe illness that is causing hospitalizations to increase and ICU admissions to increase. And we're looking at another wave of the pandemic. It's more contagious, and that's concerning. It's more serious, and that's concerning.

How effective are current vaccines against the Delta variant?

The messenger RNA vaccines (Moderna and Pfizer) are highly effective against this variant. We have that information from clinical studies and from laboratory tests of what we think the immune response should be. They're showing clinically in the U.K., where the Delta variant has been taking hold for many months now, that those messenger RNA vaccines are still highly effective ― over 80% for infection and 90% or so for severe disease. So it's still very important to take those vaccines. The Johnson and Johnson vaccine is probably going to be very effective also.

There are some early studies looking at the laboratory measurement of our immune system response that are very promising and show a really good response to the Delta variant. But we don't yet have large numbers of people in clinical studies to see what the impact of the Johnson and Johnson vaccine is on the Delta variant just yet. But we're very hopeful that that's going to be positive, as well. We want everyone who is able to get vaccinated, to get vaccinated. We've sort of stalled out in the U.S. with our vaccination rates. And nationally, only half of the population has been fully vaccinated. There are some states that are doing better and some states that are lagging. And we're seeing that those states that have lower vaccination rates are where the Delta variant is spreading the most.

What are the risks of not getting vaccinated now versus any safety or other concerns people might have about the vaccines?

People have often been waiting to see how people respond to the vaccines and what kind of side effects happen. If people have been waiting to see, now's your chance to go ahead and get vaccinated because you've seen that people do very, very well. Side effects are mild. They're self-limited. These vaccines are incredibly safe. Now is the time for people to get vaccinated. That's really the only way that we're going to stave off what could be a really devastating next wave of this pandemic.

What would you say to those who are worried about the side effects of the vaccines, such as blood clotting issues or myocarditis?

There have been a couple of more serious adverse events that were so rare that they didn't occur in those large clinical trials of more than 40,000 people. When we're talking about things that are so rare it's a few in a million, you can't detect those, even in very large clinical trials. We have these really robust surveillance systems to detect more rare problems, and we have detected a few of those now. The first one was the bleeding and clotting problem that was associated with the Johnson and Johnson vaccine, which also was seen with other vaccines in that same platform ― the AstraZeneca vaccine. And that primarily affects women under 50. It's still incredibly rare, and it is still safe for women to take either kind of vaccine.The second condition that we found through this vaccine surveillance system is myocarditis, which is associated with the messenger RNA vaccines and predominantly males. It appears to be more common in younger males, but adults, including older adults, also have experienced it.

Myocarditis is an inflammation of the heart. It's really rare, and people don't often talk about it or know about it. But it's actually a complication of COVID-19 infection. It's also a complication of other viral infections, and when people have this, they often don't know the cause of it. Unlike those clotting and bleeding disorders that were found in women and were associated with the Johnson and Johnson vaccine, this is a condition that's straightforward to identify. Standard treatment is conservative care with some medications like anti-inflammatory medications, and people do very well and go home from the hospital. And they recover fully.

I would say it is still safe, and I recommend that everyone be vaccinated, even with these rare conditions that have been found to be associated with the vaccines because the risks far outweigh the benefits of vaccination.

What would you say to those who feel that there may be long-term side effects to teenage girls who are still developing and have not yet had children?

We have not seen any concerns for reproductive side effects from any of the COVID-19 vaccines, and that includes fertility and birth outcomes. These concerns arose out of an internet rumour that is actually a complete fabrication. There is no concern for the safety of women who are pregnant or women who are trying to conceive, or for future reproductive development.