As of July 20, 2021, COVID-19 variants have been reported in numerous countries and quickly became the cause of the majority of COVID-19 cases – more information available here. The question now is: do current available vaccines still protect us against this highly transmissible variant?
Long answer short, the vaccine’s protection against severe diseases caused by variants are maintained when fully vaccinated. However, protection against infection and symptomatic diseases may be slightly reduced. Keep in mind that differences in protection depend heavily on whether people are fully vaccinated or not.
The Delta variant is much more likely to cause infections and symptomatic disease in people who are vaccinated with only one dose of Pfizer or AstraZeneca. The effectiveness of one dose is 30% against the Delta variant, compared to 48.7% effectiveness against the Alpha variant. The effectiveness of two doses is 88% for Pfizer and 67% for AstraZeneca against the Delta variant, compared to 93.7% and 74.5% against the Alpha variant [1].
There is currently no published data for effectiveness of Moderna against the Delta variant, however, there is one paper under review. This paper states that Moderna has a 72% effectiveness with one dose, but the data is not enough to provide conclusive effectiveness after receiving both Moderna doses [2]. As for the Alpha variant, there is only one report about the effectiveness of the Moderna vaccine in Qatar [3]. This research shows an effectiveness of 88.1% and 99% with one and two doses of Moderna, respectively. Although the sample size used in this study is not big enough to represent the whole population, these are promising results.
Overview of Vaccines' Effectiveness Against Two Variants
Delta Variant:
Alpha Variant:
Although fully vaccinated people can still test positive, they are still being protected towards all variants. Either one or two doses of Pfizer or Moderna can reduce the amount of virus in a patient – this means both fully and partially vaccinated people are less likely to spread COVID-19. Vaccines are proven to reduce the severity of symptoms (50% less likely to experience fever [4]) and prevent death from COVID-19. According to Dr. Anthony Fauci from the Centre of Disease Control and Prevention (CDC) at Meet the Press on July 4th, unpublished data indicates about 99.2% of COVID-19 deaths are unvaccinated, and only 0.8% are vaccinated.
Most of the data so far is focused on the efficacy of the vaccine against the delta and alpha variants, but researchers are continuously working on obtaining more information about its protection against other variants as well. In addition, according to WHO, the COVID-19 vaccines approved and in development, should offer some protection to any new variants, as they were designed to trigger a broad immune response [5]. Being fully vaccinated will decrease the likelihood of the current variants spreading, as well as prevent the inception of new variants. Lastly, those unvaccinated serve as a potential breeding ground for new variants, thus the majority of the world needs to be vaccinated to ensure that the virus can be controlled. Learn more about herd immunity in “Herd Immunity – Protecting Others by Vaccinating Yourself” and “Herd Immunity and SARS-CoV-2.”
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Written by: Hedi
Edited by: María and Natasha
BioDecoded is a volunteer group committed to sharing accurate scientific information. If you have any questions about this topic, please comment or send them to our email.
References:
Lopez Bernal, J. et al. Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant. New England Journal of Medicine (2021). https://www.nejm.org/doi/full/10.1056/NEJMoa2108891
Nasreen, Sharifa, Siyi He Msc, Hannah Chung Mph, Kevin A Brown Phd, Jonathan B Gubbay, Sarah A Buchan, Sarah E Wilson, et al. n.d. “Effectiveness of COVID-19 Vaccines against Variants of Concern, Canada on Behalf of the Canadian Immunization Research Network (CIRN) Provincial Collaborative Network (PCN) Investigators.” Available at: https://www.medrxiv.org/content/10.1101/2021.05.24.21257744v1.full.pdf (Accessed 26th July 2021)
Chemaitelly, H. et al. mRNA-1273 COVID-19 vaccine effectiveness against the B.1.1.7 and B.1.351 variants and severe COVID-19 disease in Qatar. Nature Medicine (2021). https://www.nature.com/articles/s41591-021-01446-y
Bonafede, R. & Mariotti, R. ALS Pathogenesis and Therapeutic Approaches: The Role of Mesenchymal Stem Cells and Extracellular Vesicles. Frontiers in Cellular Neuroscience 11, (2017).
The effects of virus variants on COVID-19 vaccines. World health organization(2021). Available at: https://www.who.int/news-room/feature-stories/detail/the-effects-of-virus-variants-on-covid-19-vaccines (Accessed 26th July 2021).
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