Compared to the alpha variant, the efficacy of the first dose of Pfizer and AstraZeneca is reduced compared to Delta (Photo: Pexels/Anna Shvets)
The delta variant (B.1.617.2) was first recorded in October 2020 in India. By mid-April 2021, this version of Sars-CoV-2 became prevalent in the region, and by May it had already been detected in 40 other countries. Therefore, researchers around the world have been mobilized to better understand how this strain works and how vaccines behave against it.
According to an article published in the magazine The New England Journal of Medicine This Thursday (12), the efficacy of the first dose of Pfizer/BioNTech and Oxford/AstraZeneca immunosuppressants in preventing symptomatic cases by delta may drop from 12% to 19% compared to the alpha variant (B.1.1.7), originally seen in England. However, after the two doses, the protection offered by the vaccine against delta is similar to that provided against alpha.
Delta is a factor of concern according to the criteria of the World Health Organization (WHO), and it has protein mutations. escalate Virus that can affect the immune response. In addition, there is a possibility that strains with these changes have a greater ability to reproduce, have higher viral loads and intensify transmission.
On average, the efficacy was 30.7% against delta (purple) and 48.7% against alpha (blue) after the first dose. With both doses, the rate was 79.6% for delta and 87.5% for alpha (Photo: Engagement/England Journal of Medicine)
The study was led by researchers from Public Health England, which is the UK government’s public health agency, where there has been a rapid increase in cases of delta variants. To reach the revealed conclusions, the specialists analyzed data from 150 thousand people who had been fully or partially vaccinated using Pfizer or AstraZeneca and information from 93 thousand unvaccinated individuals.
From this, it was found that regardless of the manufacturer, the first dose of the vaccine was 30.7% effective against delta and 48.7% effective against alpha. After two doses, Pfizer was 88% effective among individuals with delta disease and 93.7% among individuals with alpha. These figures in the case of AstraZeneca were, respectively, 67% and 74.5%.
In the article, the researchers noted, “After the two doses were administered, only slight differences in vaccine efficacy were observed when the delta and alpha variants were compared.” Overall, the work confirms that although immunogens may provide greater protection against alpha than delta, efficacy with the second dose remains high.
The absolute disparities were more pronounced after the first dose, highlighting the importance of full vaccination of all individuals. The authors conclude, “Our finding of reduced efficacy after a single dose supports efforts to maximize delivery of the two doses in vulnerable populations in the context of variable delta circulation.”
The findings also reinforce the need to follow non-pharmacological measures (such as the use of masks and physical distancing) between doses — and also after the second dose, because vaccines protect us, but do not completely protect against coronavirus.
Charlotte Whitmore is a contributor at Mediarunsearch.co.uk, covering a broad range of topics including news, politics, business, technology, sport, entertainment, and lifestyle. She focuses on delivering clear, balanced reporting and practical information that helps readers stay informed about current events and emerging developments. Her work highlights stories that matter to everyday audiences, with an emphasis on accuracy, relevance, and accessible journalism that keeps readers connected to the issues shaping the UK and beyond.