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The Delta Variant and Vaccine Effectiveness

August 09, 2021 16818

The COVID-19 delta variant was originally identified in India and is now the dominate variant in California and the United States. Data show that the variant is 40% to 60% more contagious than previous variants. While it is still unknown how deadly it may be, this variant has proven to spread more easily and can create more cases of severe illness and COVID-related complications. Hence, higher hospitalization rates are likely to follow. 

The delta variant should be taken seriously, as it has the potential not only to infect unvaccinated individuals more efficiently, but also to increase the evolution of new variants. Below is a brief list of frequently asked questions and answers regarding the delta variant, including what the science community knows about it so far and anticipated implications of the variant to the community locally and at large. 

Why is the delta variant more transmissible? 

Preliminary studies are still trying to determine why the delta variant is more transmissible, but it is likely because this specific variant replicates faster or more efficiently. This means individuals need a smaller viral load to become infected and to spread the virus to others while at the same time creating a higher viral load within the infected person. The delta variant may also be “stickier” and better able to bind to cells, meaning that infections can occur with shorter exposures. Delta may also be better at evading the immune system. 

How does this impact individuals who are already vaccinated? 

Two doses of an mRNA vaccine provide 88% protection from the delta variant (compared to up to ~90% protection from older variants). Published data are not yet available on the protection the one-dose J&J vaccine provides, but the manufacturer has preliminarily announced that the vaccine provides lasting and effective protection against the delta variant. These early findings not only show the effectiveness of vaccines against current variants, but they also suggest that the longevity of the vaccines might eliminate the need for booster shots in the future. 

What about boosters? Will we need them? And which ones should we take? 

According to a joint statement released by the CDC and FDA on July 8, 2021, the COVID-19 vaccines currently approved with Emergency Use Authorization in the U.S. are strong enough and effective enough to eliminate the need for a booster. This recommendation was made following an evaluation of the vaccines’ interaction with the delta variant and hours after Pfizer expressed an intention to file for approval of a third booster shot of its COVID-19 vaccine. This information will continue to be evaluated by the CDC and FDA as case rates fluctuate and virus variants continue to mutate. 

What about individuals who have natural immunity from previously contracting COVID-19? 

It is unclear how much protection natural immunity provides against the delta variant. However, studies have shown that vaccines provide better protection against variants compared to natural immunity alone. Unvaccinated individuals are at significantly higher risk to spread the virus, even if they previously had COVID-19, allowing the virus to further mutate and lead to more lethal and contagious variants. Because of this, vaccination is critical. 

Why are scientists concerned? 

Large populations remain unvaccinated, either by choice, lack of access or age (children under 12). These groups can not only be at higher risk of contracting the variant, but also serve as breeding grounds for new and more deadly variants in the future. 

For countries with lower vaccination rates, the World Health Organization recently recommended all individuals, regardless of vaccination status, to begin once again wearing masks. More locally, several California counties (Los Angeles, Yolo and Sacramento counties) followed suit by issuing recommendations for all individuals to begin wearing masks indoors to tamper the spread of the variant. 

Drug manufacturers are making claims that their vaccines are effective against the delta variant, but the WHO and increasingly more local governments are recommending that vaccinated individuals wear masks. The CDC recently recommended for vaccinated individuals begin wearing masks in most indoor situations. 

The WHO provides global recommendations, often setting the standards for countries around the world. In this case, the new WHO recommendations are aimed at countries and communities with very low vaccination rates, mostly due to lack of access (such as Brazil, India and North Korea). On July 27th, CDC updated its  guidance for fully vaccinated people, recommending that everyone wear a mask in indoor public settings in  areas of substantial and high transmission, regardless of vaccination status. This decision was made with the data and science available to CDC at the time, including a valuable public health partnership resulting in rapid receipt and review of unpublished data. In the noted California counties which recently issued new mask recommendations, the rise in reinfections of individuals who had previously contracted COVID-19 but remained unvaccinated was one of several factors considered. These recommendations, in essence, attempt to thwart a potential wave of infections that could warrant another lockdown. 

When determining the guidance you should follow in situations outside of the dental office, make sure to understand what local or state mandates are in effect, as those mandates will supersede WHO or CDC recommendations. For requirements and guidance in the dental office, refer to this  Practice Support resource

What new evidence is out there to show the safety and effectiveness of the vaccines? 

More data is available that further strengthens the safety and efficacy of COVID-19 vaccines. For instance, more than 2.8 billion vaccine doses have been administered globally since December 2020 (not including the clinical trials that started earlier that year). Additionally, there continues to be no evidence of long-term effects of the vaccines. Further, over 99% of the people who died from COVID-19 in May 2021 were unvaccinated. Lastly, since the vaccines are not 100% effective, breakthrough infections are still possible. And if breakthrough infections occur, the infection contracted may be much milder and not require hospitalization or cause death. 

The evidence is clear: COVID-19 vaccines are safe, effective and save lives. 

Visit the  Vaccine Confidence section of the CDA COVID-19 Vaccine Toolkit  for more information on COVID-19 vaccines. 


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