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A Recipe for Hope — Part 2: Vaccines and the Delta Variant


Now, after vaccines against COVID have been available for months, why do we still have so many cases of COVID? The answer involves the ability of the virus to mutate and the ability of our immune systems to respond (for both the vaccinated and the unvaccinated).

A mutation is a change in a gene that leads to a change in the protein it encodes. For example, if you have a recipe for blueberry pancakes and switch out the blueberries in your written recipe for chocolate chips, you would still be making pancakes, but they would be slightly different, and whoever uses this modified recipe in the future would be making chocolate chip (not blueberry) pancakes. The virus that causes COVID has mutated, creating different variants in the recipe. For example, the delta variant has mutations to the spike protein that make it better at getting into cells8. This, in turn, makes it more contagious and dangerous, now affecting younger people more severely9.

So how do our immune systems interact with the delta variant, especially after receiving a vaccine? Imagine by getting the vaccine you are training a little army (your immune system) on what the uniforms of an enemy army (the virus) look like. You got the patterns for their uniform and made a part of it to show your cadets what they look like so they will know who to attack when they come around. But the enemy army got a little smart and tricky. They changed their hats. Some armies may have been paying attention to other parts of the uniform and will still recognize the bad guys. Other armies may be more hesitant and confused. Still, others may have either not been paying attention or may have focused mainly on the hats and not recognize the uniforms after the change. How effective the vaccines are against both the original virus or any variant has everything to do with how your immune system responds to the spike protein your cells make after vaccination.

Accordingly, evidence shows that the COVID vaccines usually have high effectiveness and provide good protection, including against the delta variant, because they train your immune system to recognize COVID when you encounter it, though rates of effectiveness are slightly lower against the delta variant than the original alpha variant (88% vs 93.7% for the Pfizer vaccine)10. Puzzlingly, some vaccinated people can still get “breakthrough infections” of COVID. Usually the symptoms are mild, but can sometimes still be serious11. This has to do with how the patient’s immune response works (or doesn’t work) both in the face of the vaccine and the actual virus. In fact, a recent study shows that tracking the immune response via antibody production after vaccination can be predictive of how well a person is protected from breakthrough infection12.

Overall, striking evidence worldwide shows that for the majority of people, vaccines do what they were designed to do—protect against severe symptoms that lead to hospitalization and death, in the face of both the original and delta variants10,11. This is evidenced by data from a few weeks ago from the health departments of 40 states that the vast majority of patients hospitalized with COVID are unvaccinated13. In particular, 98% of patients in New Mexico hospitalized with COVID were unvaccinated13. Areas with higher vaccination rates also tend to have lower rates of COVID, showing a correlation between vaccination and protection not only on an individual level, but on a community level14.

Battling COVID at the cellular level is a fight between the virus and our immune systems. If we prepare our immune systems in advance by teaching them what the virus looks like through vaccination, they are more prepared to fight it off, and the virus replicates less. If our immune systems attack more of the virus before it spreads to others, we can protect not only ourselves but our neighbors.

Getting vaccinated is a choice—one that should be made based on facts and in consultation with medical professionals. But it is unavoidable that getting vaccinated is a choice that can benefit you and everyone around you. I chose to get vaccinated not only to protect myself but to protect my family and community.

By Caraline Sepich-Poore

Carlsbad native Caraline Sepich-Poore is a doctoral and medical student at the University of Chicago.

Part 2 of 2: For complete references, please read the article at


  1. “AMA Survey Shows Over 96% Of Doctors Fully Vaccinated Against COVID-19”. American Medical Association, 2021,
  2. 2021, Accessed 21 Aug 2021.
  3. Wolff, Jon A., et al. “Direct gene transfer into mouse muscle in vivo.” Science 247.4949 (1990): 1465-1468.
  4. Jirikowski, Gustav F., et al. “Reversal of diabetes insipidus in Brattleboro rats: intrahypothalamic injection of vasopressin mRNA.” Science 255.5047 (1992): 996-998.
  5. Cross, Ryan. “Without these lipid shells, there would be no mRNA vaccines for COVID-19.” Chem Eng News (2021): 16-9.
  6. Baden, Lindsey R., et al. “Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine.” New England Journal of Medicine 384.5 (2021): 403-416.
  7. Polack, Fernando P., et al. “Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine.” New England Journal of Medicine (2020).
  8. Scudellari, Megan. “How the coronavirus infects cells-and why Delta is so dangerous.” Nature 595.7869 (2021): 640-644.
  9. “How COVID-19 Delta Variant Is Impacting Younger People”. Https://Newsnetwork.Mayoclinic.Org/, 2021,
  10. Lopez Bernal, Jamie, et al. “Effectiveness of Covid-19 vaccines against the B. 1.617. 2 (Delta) variant.” New England Journal of Medicine (2021).
  11. “What Doctors Wish Patients Knew About Breakthrough COVID Infections”. American Medical Association, 2021,
  12. Bergwerk, Moriah, et al. “Covid-19 Breakthrough Infections in Vaccinated Health Care Workers.” New England Journal of Medicine (2021).
  13. “See The Data On Breakthrough Covid Hospitalizations And Deaths By State”. Nytimes.Com, 2021,
  14. “Where Are The Newest COVID Hot Spots? Mostly Places With Low Vaccination Rates”. Npr.Org, 2021,

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