It’s summer, and as predicted, we’re seeing yet another spike in COVID-19 infections around the nation. Cases have increased across the country, most dramatically in many Southern states, from a trough in June. Intensive care units in Missouri, Arkansas, Louisiana, and other states have been stretched to the brink. Health care workers are again exhausted, with calls for out-of-state nurses to assist in many affected areas. Mississippi is setting up a field hospital to handle their excess patients.
Much of the rise can be attributed to two forces that converged in late spring. One, the proliferation of the delta variant in the United States, which accounted for 10% of infections in early June but close to 100% of new cases by August 2021, eclipsing the previously dominant alpha variant. Two, this happened shortly after many states had lifted mask mandates, allowing unchecked transmission of the new variant. And while vaccines are now widely available and 70% of the adult population is at least partially vaccinated, many remain at risk due to purposeful rejection of the vaccine, lingering vaccine hesitancy, issues with vaccine access, or lack of eligibility, as vaccines lack authorization for anyone under the age of 12.
Delta has changed the game. So what do we know about it? And where does the pandemic go from here? Here are the best answers we have so far.
1. Where do variants come from?
A spate of new variants of SARS-CoV-2 was detected in multiple countries in the fall of 2020 and winter 2020–21. The delta variant (also known as B.1.617.2) was one of these which emerged and spread globally. “A variant is just a mutation observed within the SARS-CoV-2 genome,” Ryan McNamara, Ph.D., a research associate in the Department of Microbiology and Immunology at the University of North Carolina at Chapel Hill School of Medicine, tells SELF. Many mutations will be either neutral or harmful to a virus. But occasionally, a mutation or combination of mutations can allow the virus to infect a host more efficiently. Some variants may also cause more severe disease in the host, as was suggested with the alpha variant, B.1.1.7.
If these variants increase in the population, the World Health Organization (WHO) or other health agencies may start calling them variants of concern. A variant of concern designation is given for one or more of several reasons. The combination of mutations in a variant lineage may lead to increased transmissibility or increased virulence (or both). It could result in a variant that is not recognized by current diagnostic measures. Variants of concern may also show reduced effectiveness to vaccines or treatments. There are currently four designated variants of concern: alpha (B.1.1.7, first identified in the United Kingdom), beta (B.1.351, first identified in South Africa), gamma (P.1, first identified in Brazil), and delta (B.1.617.2, first identified in India).
2. Why is delta the big bad right now?
The emergence of new variants was expected as the pandemic raged on. As the virus infects more and more hosts, copying errors occur as the virus replicates, and sometimes these errors benefit the virus, allowing these variants to outcompete the other viruses in the population. This previously happened with the alpha variant, which Delta has replaced in many countries. “I think what we’re seeing with the emergence of so many new variants is that the virus is still adapting itself to human-to-human transmission,” says Dr. McNamara. “This happens when a virus spills over into a new host. The originally circulating virus was evolutionarily adapted to transmission in a different host. When a virus finds a new host, it needs to fine-tune itself to establish itself. We are that new host.”
Globally, delta has been slowly increasing in prevalence since it was first identified in India in 2020. “Its early spread seemed to be focused in India when overall COVID-19 cases were declining,” says Dr. McNamara. “It displaced other circulating SARS-CoV-2 variants and become the predominant form in India, and played a major role in the surge they experienced in the spring.”
Delta, like alpha before it, is more transmissible than previously circulating versions of SARS-CoV-2. “There is data suggesting that the delta variant is about twice as contagious as previous variants and some data from other countries suggesting it may cause more severe illness than prior strains of the virus in unvaccinated individuals,” explains Krutika Kuppalli, M.D., infectious disease physician and vice chair of the Global Health Committee of the Infectious Disease Society of America, tells SELF. Breakthrough infections—infections in individuals who have been fully vaccinated—also seem to be more common with delta than with the prior alpha variant. Dr. Kuppalli notes that these vaccinated individuals may still transmit the virus, which has led the CDC to reinstitute their mask recommendations for vaccinated individuals in areas where there is high viral transmission.
While we haven’t worked out all the details for why delta is better at transmission than prior variants, it contains several mutations within the spike protein of the virus, which is the protein responsible for binding to cell surface receptors of the host. “Some of the mutations observed in delta have been shown to increase the virus’s ability to bind to the human receptor, ACE2,” says Dr. McNamara, which could make transmission more efficient and play a role in its rapid global spread.
3. How much protection do COVID-19 vaccines offer against Delta?
The currently authorized vaccines were developed and tested while the early strains of SARS-CoV-2 were circulating. By the time of their release in late 2020 and early 2021, the alpha variant had begun to spread in the U.S., with the delta variant emerging in the U.S. in the late spring. This has complicated our ability to study how well the vaccines are working since each variant has different properties that may affect vaccine effectiveness. Studies done early this spring while the alpha variant was dominant may not be applicable to the delta variant. Still, even against the delta variant, our vaccines appear to be holding up well. Dr. McNamara says, “The two-dose mRNA vaccine of BioNTech/Pfizer was shown to be 88% protective against symptomatic COVID-19. That is just incredible given how recently this virus came into human circulation.” But Dr. Kuppalli cautions that for that degree of protection, both doses of an mRNA vaccine are necessary and a single dose is much less protective.
She also says that recent research has demonstrated that the single-dose Johnson & Johnson vaccine appears to be working well in this arena. “The recently released Sisonke data from South Africa demonstrates the J&J vaccine is effective against the delta variant, showing that in 500,000 health care workers it was 71% effective in preventing hospitalization and 96% effective in preventing death.” This data has yet to be peer-reviewed and published, however—but it’s still promising.
4. Should people be doing anything differently safetywise now that Delta is circulating so widely?
While the circulating variants may have changed, public health recommendations remain largely the same for the delta variant as they did for alpha and the original virus.
“Vaccination is a protection tool we have now that we didn’t have with the original virus, so getting vaccinated is the big thing we can be doing differently now. The more layers of protection that can be added, the better,” says Dr. McNamara. He added that his behavior has changed little since the start of the pandemic. “I still wear masks when I expect to interact with others, I avoid clustered, indoor gatherings, I frequently get my groceries delivered, I avoid unnecessary travel, etc.”
In addition to vaccination, Dr. Kuppalli recommends a well-fitting face mask for everyone, vaccinated or not, that has a good seal and covers your nose and mouth. “I would recommend you wear it inside and outside when in crowded places, to avoid crowds, and to practice physical distancing.”
5. What about kids and the delta variant?
As the new school year begins, parents are dealing with a huge amount of uncertainty regarding children and the delta variant, particularly in areas where surges are happening and mask mandates have vanished. Dr. Kuppalli notes that delta is hitting kids hard. “Our hospitals are seeing more children this time around, and make no mistake: Kids can get very sick with this virus,” Dr. Kuppalli says. “We are seeing cases of MIS-C and we are still learning about the long-term effects of this virus in kids.” She cautions that the variant seems to have a predilection for the brain, and long-term research on how that may affect children in years to come is lacking.
Dr. McNamara notes that delta just emphasizes once again the importance of vaccination of those eligible, which currently includes those age 12 and up: “For those that are not yet eligible for the vaccine, the best thing we can do for them is to shield them by protecting ourselves and not putting them at risk. We know that vaccinations and other nonpharmaceutical interventions like mask wearing and maintaining distance between each other can reduce transmission risk.”
6. Do we need to be concerned about other variants, like delta plus and lambda?
The “Delta plus” variant (which is actually three different, related variants, called AY.1, AY.2, and AY.3) contains additional mutations beyond those which characterize the original delta variant. Even though that “plus” moniker is there, experts generally lump “delta plus” together with the delta variant in terms of both risk and transmission. The CDC and WHO don’t categorize them separately, and there has not yet been much sequencing done to detect delta plus versus delta in COVID-19 cases. The lambda variant emerged in Peru in December 2020 and has caused more than a thousand cases of COVID-19 in the United States. It is currently designated a “variant of interest” by the WHO, but not yet a “variant of concern” as it has not definitively shown increased transmission or severity of disease in those infected.
“I do not see a variant emerging that abolishes protection offered through the vaccines,” says Dr. McNamara. “The vaccines are so incredibly protective against COVID-19 that the mutations needed to bypass them completely would most likely make the virus inert. So I think that any discussion on the emergence of future variants needs to be grounded in the reality that the vaccines we have confer protection against every variant we’ve seen.”
But this doesn’t mean we should be complacent. Every new host infected allows the virus additional opportunities to evolve, so continuing to vaccinate people and employ other interventions to reduce spread remains critical, especially because some people will remain unprotected. “Some populations cannot be vaccinated or have low responses to the vaccines due to underlying conditions. If we can reduce our own risk of contracting and transmitting SARS-CoV-2, then we can reduce their risk as well.”
7. What about boosters in light of delta—do we need them?
The possibility of a third dose of vaccine has been raised, with the idea of providing additional protection against new variants. However, the FDA has not authorized a third dose of mRNA vaccines (Pfizer and Moderna) for healthy individuals, and most experts do not think it’s warranted at this time. A second booster dose for the single-dose Johnson & Johnson vaccine is also not yet authorized.
Instead, we should stay on top of other safety measures, suggests Dr. Kuppalli, including masks, distancing, and avoiding crowds. Dr. McNamara agrees that the vaccines are still holding up well, even for those who were vaccinated at the beginning of the year with the most time for the vaccine protection to wane. Instead of additional shots for most individuals, he suggests the possibility of a targeted third dose in individuals who may not respond well to vaccines, including older individuals and those with underlying conditions that may compromise the immune system. “The best way to stop delta and other variants from emerging is to encourage vaccination in those who have yet to be vaccinated,” he says.
That unvaccinated group includes those around the globe who have yet to access the vaccine. Dr. Kuppalli cautions that leaving these individuals behind could lead to the rise of additional dangerous variants. “In order to prevent that, we need to focus on vaccine uptake not only in our country but around the world,” she says. “We have to get levels of circulating virus down around the world and not just in the U.S.”