SARS-COV-2 Delta Variant: The Uninvited Guest and How to Deal with it.

Picture source: WHO

SARS-CoV-2 is an RNA virus- ergo it was expected to mutate. Unfortunately, about 163 million Americans had already gotten the shot before the new Delta (B.1.617.2) variant emerged. This new variant, first identified in India, was seen to be much more contagious than the previous versions. The spreading of misinformation in public and the decreasing trust in the vaccines from J&J, AstraZeneca, Pfizer-BioNTech, and Moderna is a growing issue, especially because the extent of disease severity is much higher in unvaccinated individuals as compared to the vaccinated ones. Contrary to what was rumored, all three of these vaccines turned out to provide effective protection against the Delta variant.

J&J vaccines (Ad26.COV2.S) were marketed with the benefits of just one dose instead of two and a longer shelf life than the mRNA vaccines, when refrigerated. The phase 3 trial has already shown that the Jannsen vaccine is 85% effective against severe disease, hospitalization, and death. A recent pre-print study collected sera samples from 8 participants of the Phase 3 trial who received one shot of the J&J vaccine. Their sera seemed to neutralize beta and gamma variants of SARS-CoV-2 and their mutants better than Delta. Vaccines stimulated T cell responses and antibodies which grew more effective over time (8 months vs 1 month). A second dose is expected to boost those immune response levels to even higher amounts, as shown in another pre-print study where the Pfizer-BioNTech vaccine (BNT162b2) and the Moderna vaccine (mRNA-1273) were shown to elicit more neutralizing antibodies against Beta, Delta, Delta plus, and Lambda variants than the Jannsen vaccine.

A recent study published in the New England Journal of Medicine compared the effectiveness of the Pfizer-BioNTech and AstraZeneca vaccine (ChAdOx1) against the Delta variant to their effectiveness against the predominant Alpha variant. This was done by whole-genome sequencing of the viruses in symptomatic patients of England and correlating the results with the patient’s vaccination status. After just one dose, the effectiveness of the vaccines against the Alpha variant was found to be 48.7% whereas the effectiveness of protection against the Delta variant was only 30.7%. Bringing in some good news for the population vaccinated with both the doses of the Pfizer-BioNTech vaccine – two doses had 93.7% effectiveness against Alpha variant and 88.0% effectiveness against Delta variant. On the other hand, two doses of the AstraZeneca vaccine provided 74.5% and 67.0% effectiveness against Alpha and Delta variants, respectively.

Researchers have demonstrated that the Delta variant can escape host antibodies targeting RBD Spike and non-RBD epitopes which may be the reason behind its fast spread. Delta variant was resistant to neutralization by monoclonal antibodies against the N terminal domain as well as receptor-binding domain (RBD), which were found to be functional against the Alpha variant. The antibodies present in the sera of convalescent patients or people who received only one dose of the Pfizer-BioNTech or AstraZeneca vaccine were ineffective towards the Delta variant. Relative to the Alpha variant, neutralizing antibodies produced after the second dose of both Pfizer-BioNTech and AstraZeneca displayed a reduced titer against the Delta variant (and even more reduced titer for Beta variant).

While we wait for more details on the effectiveness of the Jannsen vaccine against different strains and the immune response studies of the mRNA and AstraZeneca vaccines against Delta variant, the results shown till now seem to be quite promising for the vaccinated population. However, it should be taken into consideration that the effectiveness is only being measured by the ability of the vaccines to prevent symptomatic disease or hospitalizations. Research on preventing the SARS-CoV-2 replication/translation/assembly/release is still ongoing and may take decades to uncover. That means that the virus will keep on transmitting among us and mutating until it creates more new variants. There may be a point in time where we would need more booster doses or seasonal vaccinations like for influenza vaccine. Meanwhile, the best way to stay safe and prevent the spread is by wearing a mask indoors, staying 6 feet apart, and maintaining proper hygiene. Not to forget, the best way to prevent hospitalization due to moderate or severe COVID-19 is by getting vaccinated. The new variants is speculated to cause the “pandemic of the unvaccinated” because statistics from CDC show that infections, hospitalization as well as death rates are much lower in vaccinated individuals as compared to the unvaccinated. Finally, we want our audience to prevent spreading of misinformation and always verify news before believing them as facts. Stay safe!

Sources are underlined in the article.

Article author: Sutonuka Bhar. Sutonuka is a PhD candidate majoring in Medical Microbiology and Bacteriology at the University of Florida. Her work focuses on host immune responses against viruses and bacterial membrane vesicles.

Check out Antibuddies’ blog post “SARS-CoV-2 Delta Variant: The Uninvited Guest and How to Deal with it.”

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