What to know about the COVID-19 delta variant 

July 12, 2021

Q&A

The COVID-19 delta variant is the highly contagious and currently dominant virus strain in the United States. Eugene Wu, associate professor of biology and biochemistry, studies viruses, and he recently talked about what makes the delta variant more dangerous and how to combat it.  

Can you explain how the delta variant came about? 

Coronaviruses are a class of viruses with RNA as a genome. Copying RNA is a relatively inaccurate process that results in some small number of mutations being made. Many of the mutations die off, but some mutants are passed on, and even make the virus more contagious. When a mutant virus shows an enhanced ability to spread and starts increasing in prevalence in a geographical area, the World Health Organization has started assigning a Greek letter to the new variant of concern. The so called delta variant contains four key mutations that change the sequence of the spike protein, the big clubs on the outside of the virus, along with many other signature mutations elsewhere in the genome. This variant is different because it makes the virus stickier, more infectious, and more contagious.  

Can you get the delta variant if you’ve been vaccinated? 

This is a question that scientists are actively working on. As a product of a tremendous amount of farsighted research over the past two decades, scientists were able to create, test, and manufacture working vaccines against COVID-19 using its spike protein sequence in record time. The two-dose Pfizer/BioNTech and Moderna vaccines decrease your chance of getting COVID-19 by more than 94%, and the single-dose Johnson & Johnson vaccine by about 66%.  

These vaccines teach your immune system about the spike protein of the original virus from a year and a half ago. Your  white blood cells churn out billions of antibody proteins that stick to the spike protein, thereby deactivating the virus. When the spike protein sequence changes, it’s possible that the antibodies targeting the original virus no longer stick to the new variant. Within the last few weeks, scientists have released preliminary data showing that vaccination with two-dose mRNA vaccines produces plenty of antibodies to catch and block the delta variant to almost the same degree. According to a study out of the United Kingdom, the Pfizer-BioNTech vaccine still reduces your chance of catching the delta variant by 88% and reduces your chance of being hospitalized by the delta variant by 96%, which is still extremely good! Bottom line, the vaccines still work almost as well to protect against the delta variant, despite the changes in its spike protein. 

Are unvaccinated people at particular risk? 

You can definitely get infected by the delta virus if you haven’t been vaccinated. The delta variant is estimated to be about twice as contagious as the original SARS-CoV-2, although that is hard to quantitate. We know that when the delta variant shows up in a country, it quickly expands to become the cause of a substantial or a majority of cases within a matter of weeks, meaning the delta variant is outgrowing other versions of the virus.  

The vast majority of infections by the delta variant are among the unvaccinated population. For example, in a case in Australia, everyone who attended a birthday party was infected with the delta variant except for the six attendees who were vaccinated. There is also some indication that infections by the delta variant result in double the risk of hospitalization, suggesting that it’s not only more contagious, but it’s making people sicker.  

What else should people know about this? 

Variants will arise naturally as a result of evolution. The virus is adapting to humans in real time. The fewer chances we let the virus transmit, the fewer chances the virus gets to change. Not only will vaccination protect yourself, it protects everyone else by making it less likely for variants to arise. Get vaccinated, for yourself, and for all of us.