Delta Variant Q&A

Delta Variant Q&A title=
Delta Variant Q&A
19 Comments
Reads 5529

By Andrea Estrada, UC Santa Barbara

The emergence of the highly transmissible SARS-CoV-2 Delta variant has raised a host of questions about the variant itself, the effectiveness of vaccines in preventing serious illness, and the impact on unvaccinated individuals.

To better understand the data related to this new, virulent strain and how guidelines and protocols should be adjusted to mitigate its spread, The Current has brought together a panel of experts that includes Carolina Arias Gonzalez, a virologist and assistant professor of molecular, cellular and developmental biology; Stuart Feinstein, campus COVID-19 response coordinator and professor of molecular, cellular and developmental biology; and Scott Grafton, M.D., campus COVID-19 mitigation program manager and professor of psychological and brain sciences.

What is the Delta variant and why is it dominant?

The Delta variant is a new strain of the SARS-CoV-2 virus that causes COVID-19. As viruses copy their genome during infection, errors can be incorporated that in some cases change the behavior of the virus. As the mutations accumulate in the genome, new versions of the virus — variants — are established. In the case of SARS-CoV-2, the Delta variant has mutations that make the virus more contagious. The reasons behind the increased transmissibility of Delta are still under investigation, but we know that some of the mutations in this variant have changed how the virus interacts with the cell during their first encounter, and allow the virus to bind tighter to the cell, making infection easier.

Delta is by far the most widespread strain throughout the U.S. and in Santa Barbara County.

Does the increasing percentage of vaccinated people getting breakthrough Delta variant infections mean the vaccines are not as effective as previously believed?

This is a misleading way to think about vaccine effectiveness. If the entire population is vaccinated, then 100% of cases, whether Delta or other variants, are “breakthrough” infections. A more important number to track is the number of new cases per 100,000 vaccinated people per day. In Santa Barbara County we have approximately 7.5 cases per 100,000 vaccinated people per day. Of note, this is more than 4 times less than the number of unvaccinated people becoming infected — that number is approximately 38 cases per 100,000 unvaccinated people per day.

The vaccine provides excellent protection against all known strains of SARS-CoV-2, including Delta. A study from UC San Francisco health care workers found that vaccinated workers were 5 times less likely to contract COVID-19 and 25 times less likely to be hospitalized for it than their non-vaccinated colleagues.

We’re reading in the media that the vaccines are only 67% effective at preventing severe illness from the Delta variant. Is that true?

That number is misleading because it fails to consider that both the vaccination rates and the risk of severe disease change from young adulthood to old age. Once these effects are taken into account, multiple recent real-world studies show the vaccines are over 90% effective at preventing severe illness in all age groups.

How worried should those who are fully vaccinated be about contracting COVID-19?

The upward trend in national statistics is being driven almost entirely by outbreaks in places with low vaccination rates. While the frequency of COVID-19 hospitalizations and deaths are greatly reduced by the vaccine, unvaccinated Americans now account for almost all recent COVID-19 cases and related hospitalizations and deaths.

Does the Delta variant cause more serious disease in adults?

A recent analysis by the Centers for Disease Control and Prevention integrates information from Canada, Singapore and Scotland and finds higher odds of hospitalization, ICU admission and death from the Delta variant in unvaccinated people compared to the Alpha variant (also known as B.1.1.7), which was the dominant variant in the United States before Delta’s rise.

Does the Delta variant make children sicker than the previous variants?

In the spring of 2021, prior to the arrival of the Delta variant, 0.8% of children diagnosed with COVID-19 were admitted to the hospital. Since the arrival of the Delta variant, this has increased slightly to 0.9%. What has increased is the overall number of infected people in a community, including children, because of the Delta variant.

Does the COVID-19 vaccine prevent the spread of asymptomatic, mild or moderate COVID-19?

Vaccines were approved based on their ability to prevent severe infections — that is, hospitalizations and/or death. Before the arrival of the Delta variant, there was very encouraging evidence that the vaccines were approximately 90% effective at also preventing asymptomatic, mild or moderate infections. Recent evidence suggests that with the emergence of the Delta variant this effectiveness for less than severe disease has been reduced to about 66%. Relative to most vaccines, including the flu shot, this is still very strong protection. But the most important point to remember is that the vaccines are especially effective at preventing the most serious outcomes, that is, hospitalization and death.

Recent data also suggest that the duration of viral shedding following infection with the Delta variant is shorter in vaccinated individuals. A shorter infection may help reduce the chances of secondary transmission.

We’re hearing a booster may be necessary for maintaining protection against COVID-19. What is the basis for recommending booster vaccinations?

Solid, real-world and laboratory evidence shows that boosters can add immunity for those who are immunocompromised. There is general consensus among those in the medical community that those individuals should receive an additional dose, or “booster.” For everyone else, evidence as to whether or not boosters will make a big difference in preventing severe, mild or asymptomatic infection is still emerging. We know severe illness from COVID-19 is more common the older one gets. This is a basis for the emerging recommendation that those over 65 get a booster. Another argument in favor of boosters is a concern that the initial vaccine might lose some of its effectiveness after many months. This has led to a consideration of recommending the vaccine booster for everyone 8 months after their initial doses.

Are booster shots safe?

Because boosters have been rolled out only recently, we don’t yet have a strong safety signal to answer this question. However, remember that a booster is just another injection of the same material as in the earlier vaccine injection(s) — not something different. Notably, though, the safety signals for the RNA-based vaccines from over 180 million recipients was outstanding. Furthermore, immunocompromised individuals who received an extra dose in clinical trials tolerated it well.

Is there another variant on the horizon that looks worse than the Delta variant?

The Lambda variant received a lot of attention as it spread rapidly and case counts climbed in South America. However, laboratory studies of its ability to bind to human cells or to escape neutralizing antibodies show it is very similar to Delta. There is no surveillance data so far that shows it can out-compete the Delta variant in North America.

If I can still get infected with the Delta variant after I’m fully vaccinated, why bother getting vaccinated in the first place?

Vaccination greatly reduces your chances of developing serious illness. Presently, the vast majority of serious illness and hospitalizations are occurring among unvaccinated individuals.

If an individual is fully vaccinated and is exposed to someone who has been infected with the Delta variant, does that individual still need to get tested and quarantine for 14 days?

Guidance from the CDC for vaccinated individuals with a known exposure to any variant of COVID-19 recommends testing 3 to 5 days following exposure, whether or not they have symptoms. They should wear a mask indoors in public for 14 days following exposure or until they receive a negative test result, and they should isolate for 10 days if they have a positive test result.

How effective are masks?

Modeling studies from colleagues at UC San Diego show that the benefit of indoor masking on transmission of the virus — including the Delta-variant — can result in 4 times fewer cases on campus. By using a good two-layer mask indoors we can all make a powerful contribution to the community.

COVID-19 cases come in spikes over a few months. What reverses the growth of cases in a community?

Intuitively, you might think the reversal happens because everyone is immunized by a vaccine or prior infection. However, real-world estimates suggest that the reversal occurs because people change their behavior. As local conditions worsen, people become more cautious. This further supports the importance of masking, distancing and spending less time indoors.

How do conditions in Santa Barbara County compare to “hot spots” around the country?

In late August, Santa Barbara County was experiencing about 21 new cases per 100,000 people per day. And the North County has a higher rate of new cases than does the South County. By comparison, Harris County, Texas, encompassing the greater Houston metropolitan area, was experiencing 334 new cases per 100,000 people per day. Imagine if Santa Barbara County had 12 times as many cases as it currently does. The differences are fully accounted for by the choices we all make in facing this pandemic.

How does the campus assess the COVID-19 risk associated with in-person instruction?

The most important information we have to work with is the number of new positive tests (identified using high performance testing methods) in the campus community that are diagnosed each day. This number can then be normalized in a variety of ways — cases per 100,000 people per day; % positive cases; new cases per 100,000 people per day averaged over the prior week. The CDC provides clear guidelines for using these measures to operationally define conditions of “high” virus transmission in the community. Similar metrics from the County serve as an important point of reference for detecting an unacceptable growth in cases that are specific to the UC Santa Barbara community. Critically, growth rates in these metrics, i.e. their trends are as important as absolute thresholds in identifying conditions of high virus transmission. 

In general, the measures described above are biased to count people who develop symptoms. By also initiating a campus testing program with weekly random sampling of a fraction of the campus community, we overcome these potential sources of bias and better assess the underlying change in the prevalence of disease, including asymptomatic cases. 

news.ucsb.edu

Login to add Comments

19 Comments

Show Comments
Byzantium Sep 03, 2021 11:05 AM
Delta Variant Q&A

The real disease is mutual bloviating. All sound and fury, signifying nothing.

GeneralTree Sep 03, 2021 10:52 AM
Delta Variant Q&A

VOR continually defending Florida is a great laugh. Please move there and take your unvaccinated family with you. Spreaders of intentional health-disinformation like you are terrorists.

Voice of Reason Sep 03, 2021 11:03 AM
Delta Variant Q&A

you're not reading my comments if you think my family isn't vaccinated.

3P14159 Sep 03, 2021 05:51 AM
Delta Variant Q&A

the fit will survive. the unfit will die off at a faster rate. part of being "fit" is being vaccinated. easy peasy.

Chevy67 Sep 02, 2021 04:49 PM
Delta Variant Q&A

So much good information in this article and so much misinformation by two bloviating commenters

dukemunson Sep 02, 2021 06:58 PM
Delta Variant Q&A

I love that guy at the brewery!!! Though debating more about masks and emotional support animals then rent control…

Chevy67 Sep 02, 2021 06:30 PM
Delta Variant Q&A

You seem like the guy who sits alone at a brewery and starts debating strangers sitting next to him on things like rent control and mask importance.

Voice of Reason Sep 02, 2021 05:00 PM
Delta Variant Q&A

Please share the misinformation in my post, unless you were talking about @4:43. Also, SBGetsalong was just asking questions. It's a good sign of how messed up things are right now when asking questions is "misinformation".

a-1630626274 Sep 02, 2021 04:44 PM
Delta Variant Q&A

Two new studies out, both of which mention the importance of retaining nonpharmaceutical interventions like masking and distancing in light of the Delta variant:

https://www.nejm.org/doi/full/10.1056/NEJMc2112981

https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00460-6/fulltext

SBLetsGetAlong Sep 02, 2021 04:09 PM
Delta Variant Q&A

“ The vaccine provides excellent protection against all known strains of SARS-CoV-2, including Delta. ”
Then why do Vaccinated people need to wear masks and social distance?
Why are unvaccinated being blamed for Delta? Delta has existed in India and over seas for almost a year, per this report Vaccinated can & do spread the disease.

Why did the CDC announce in May that they stop tracking breakthrough cases unless they resulted in hospitalization or death? Do t they want to know how many people are still getting Covid?

Per CDC one shot provides 80% protection.
So why are one shot vaccinations considered unvaccinated if they get Covid?
Why is a two shot person considered unvaccinated if they get Covid within 2 weeks of the second shot?

Jan-Feb the US had an 82% reduction in cases. The US population was 6% vaccinated.
So the vaccination is not responsible fir the 82% decline in cases.

The country was 50% fully vaccinated in June. Plus another 20% that had one shot providing 80% protection. But in July case rates started climbing and in August after 70% of the country was vaccinated we saw record high case rates that haven’t been seen since the peak.

Why? The Vaccines don’t work?
Look at Israel the most vaccinated country with high case rates.

Will a third shot really help when two shots didn’t? Any science on that!

GeneralTree Sep 03, 2021 10:59 AM
Delta Variant Q&A

"Then why do Vaccinated people need to wear masks and social distance?"
Some conditions make a breakthrough infection more likely in a vaccinated person: more virus circulating in the community, lower vaccination rates and more highly transmissible variants. If vaccinated people can get infected with the coronavirus, they can also spread it.

"Why are unvaccinated being blamed for Delta?"
If the virus has an easy host, such as an unvaccinated individual, then it is easy for it to mutate into a more contagious and virulent form.

The rest of your diatribe aren't really seeking answers - more like you pushing agenda with a phony question. Typical.

letmego Sep 03, 2021 09:40 AM
Delta Variant Q&A

"Then why do Vaccinated people need to wear masks and social distance?" Because you can still catch and spread the virus, though it is happening at a much lower rate.

"Why are unvaccinated being blamed for Delta?" The surge in cases is happening mostly in areas where people are unvaccinated, and Delta is far more transmissible than Alpha.

"Why is a two shot person considered unvaccinated if they get Covid within 2 weeks of the second shot?" They are considered not FULLY vaccinated because full protection occurs 14 days after the second shot.

"Jan-Feb the US had an 82% reduction in cases. The US population was 6% vaccinated.
So the vaccination is not responsible fir the 82% decline in cases." January was the nation's post-holiday peak. The nation shut down all over again in response. Or, many places did. Schools were closed. Even I started using Instacart for groceries.

"The country was 50% fully vaccinated in June. Plus another 20% that had one shot providing 80% protection. But in July case rates started climbing and in August after 70% of the country was vaccinated we saw record high case rates that haven’t been seen since the peak.
Why? The Vaccines don’t work?" - Is this really a question? Delta is the reason, because it is more contagious than Alpha. Instead of 1 person infecting 2.5 people on average, they can infect 4 other people.

Luvaduck Sep 03, 2021 08:40 AM
Delta Variant Q&A

Some politicians aren't interested in anything but staying on the gravy train. Don't expect ethical behavior or community protecton from them. Essentially, they're sociopaths.

Luvaduck Sep 03, 2021 08:36 AM
Delta Variant Q&A

Masking requirement: If all people were honest and masked if they were not vaccinated, it would be OK for others not to mask. Some anti-vaxxers wear them under their noses if that is a condition of entry as soon as they are inside. Their political statement puts others in jeopardy, so vaxxed or not, wearing a mask that protects YOU is the intelligent thing to do.

a-1630642794 Sep 02, 2021 09:19 PM
Delta Variant Q&A

Thanks for the rebuttal. I rarely agree with you, but this was well-done.

OGSB Sep 02, 2021 05:51 PM
Delta Variant Q&A

Sb, Well the Biden Admin said we all need a booster shot. That's before the silly FDA had a chance to vet the idea. Follow the science, right?

sacjon Sep 02, 2021 05:02 PM
Delta Variant Q&A

"Remember all that pointing "look FL they're all going to die" only for to ignore it a few months later with CA spiked (even higher) and FL was considerably lower." - How's Florida doing these days? Yeah, yeah.... that was then, this is now, but still. How's Florida and Texas?

a-1630626230 Sep 02, 2021 04:43 PM
Delta Variant Q&A

I guess you haven't been following DeSantis' throttling of COVID data releases from Florida Health to try to hide the explosion of cases and increase in the death rate as the hospitals got overloaded. Some nice articles in the Miami Herald exposing his behavior.

Voice of Reason Sep 02, 2021 04:37 PM
Delta Variant Q&A

Let me take shot SBGetsalong.
Then why do Vaccinated people need to wear masks and social distance? vaccine signfincitaly reduces the severity of the infection but unfortunately doesn't totally eliminate the ability to spread it in some people, so continuing the theme of "out of an extreme overabundance of caution" you have to mask up.
Why are unvaccinated being blamed for Delta? People really like to blame others, even when it's outside of the others control, as it helps put them at ease and provides an outlet for their frustrations. Human nature I guess.
Why did the CDC announce in May that they stop tracking breakthrough cases unless they resulted in hospitalization or death? I don't believe this is still accurate and even at the time it was a positive test AND a symptom. The metrics for what is a covid case, a covid death (with covid or from covid), a covid hospitalization (coming to the hospital for something else then testing positive), and an effective PCR cycle threshold, has been an inconsistent and poorly message mess since we started.
One shot / two shoot considered unvaccinated <2 week? They have to draw the line somewhere and the full treatment if you will, seems like a reasonable place.
(varying spikes/decreases in cases with increasing vaccination)Why? The Vaccines don’t work? 1) seasonality based on the geographic area/climate and 2) as an area sees a spike there is a natural path it takes and reaches a point where the rapid growth can't be sustained through ever increasing infections. Remember all that pointing "look FL they're all going to die" only for to ignore it a few months later with CA spiked (even higher) and FL was considerably lower.
Will a third shot really help when two shots didn’t? That is still being studied but initial data says yes. Actually the reason why two top FDA officials resigned this week, White House was pushing booster shots and the FDA hadn't even reviewed all the data yet.

Please Login or Register to comment on this.