After the dramatic loss of human lives and the existence of enterprises in the first and second waves of the COVID 19 pandemic, there are speculations that soon we have to face the consequences of the third wave, which may hit human civilization even harder than the first two. The only saviour in this harsh situation that stands out is the vaccine. With the approval of different vaccines, the vast conflict arises which vaccine is effective against the evolving mutations of SARS-CoV-2. It is not only the concern of the ordinary public but the scientists who are working to solve COVID-19 related problems. Fortunately, this article focus on clearing some of the doubt about which vaccine is effective against the delta variant of COVID-19.
Why delta variant of Covid-19 is the concern of the world?
Undoubtedly, all the variants of corona are deadly to human beings, but the focus has shifted to the delta variant being the most dangerous of all. Why is it so? That’s because the delta variant has undergone mutations in spike protein T19R, 157-158, L452R, T478k, D614G, P681R, and D950N. While several of them may affect the key antigenic region of receptor binding protein (452 and 478), P681R is at S1 & S2 cleavage site, and the mutation at this site may have higher replication. The increase in replication will increase the viral load, thus exacerbating the immune system.
Vaccines efficient against delta variant of SARS-CoV-2
The study published in the New England Journal of Medicine and bioRxiv demonstrates the efficacy of Pfizer–BioNTech (BNT162b2), AstraZeneca (ChAdOx1, branded as Covishield in India), and Covaxin (BBV152) against delta
variant of SARS-CoV-2. Bernal et al., 2021, conducted a study using an unbiased test-negative case-control analysis comparing vaccination status in person with symptomatic Covid-19 with the person who reported symptoms but had a negative test when delta variant began circulating in the UK. Moreover, the samples used for studies were differentiated between alpha and delta variants by TaqPath assay (test for a spike, nucleocapsid, and ORFlab). Both vaccines AstraZeneca and Pfizer’s performance was notably lower in delta variants (approximately 30.7%; 95% Confidence interval [CI], 25.5 to 35.7) than an alpha variant with an average efficiency of 48.7% (95% CI, 45.5 to 51.7) after the first dose. In contrast, a slight difference in vaccine efficiency between delta and alpha variants after the second dose. At the same time, Pfizer showed a slightly higher capability of 93.7% (95% CI, 91.6 to 95.3) than AstraZeneca efficiency of 74.5% (95% CI, 68.4 to 79.4) against delta variant of SARS-CoV-2, and the same trend was observed in case of an alpha variant as well.
In India, studies conducted by Yadav et al., 2021, sera samples obtained from COVID-19 recovered people infected with Lineage B.1.1.7, B 1.351, B.1.1.28.2, and B1 PRNT50 (Plaque reduction neutralization test) against B.1.617 (delta) variant performed, and the results of which compared with results of sera samples of collected from vaccine (Covaxin) recipients. The neutralization efficiency of sera of vaccinated individuals (GMT values 88.48; 95% CI 62.02 to 126.2) was similar to that of recovered cases (GMT 86.85; 95% CI 52.04 to 144.9) against delta variant. Furthermore, the finding supports the potency of Covaxin to neutralize the range of variants, including delta variant of SARS-CoV-2, thus building much -needed boost to the COVID-19 vaccination program in India.
To conclude, both the studies support these vaccines as an alternative to protect populations vulnerable to delta variant and prototype strains but more effective after the second dose, thus encouraging the efforts to maximize vaccination drive. The difference in neutralization efficiency stated in this article is statistical data (from reference research article) to determine the ability to protect the people against Covid-19 and not establish hierarchy.
Reference
Bernal, J. L., Andrews, N., Gower, C., Gallagher, E., Simmons, R., Thelwall, S., … & Ramsay, M. (2021). Effectiveness of COVID-19 vaccines against the B. 1.617. 2 variant. medRxiv.
Yadav, P., Sapkal, G. N., Abraham, P., Ella, R., Deshpande, G., Patil, D. Y., … & Mohan, V. K. (2021). Neutralization of variant under investigation B. 1.617 with sera of BBV152 vaccinees. bioRxiv.