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AstraZeneca vaccine is 92% effective against hospitalizations due to Delta variant


Cristina Azevedo (Fiocruz News Agency)


A study by Public Health England (PHE) showed that applying two doses of the AstraZeneca vaccine results in 92% effectiveness against hospitalization due to the Delta (B.1.617.2) variant of the Sars-CoV-2. The variant, formerly known as the Indian variant, has been spreading through the United Kingdom like wildfire and there have been confirmed cases in Brazil as well. The vaccine has also shown high effectiveness against the Alpha (B.1.1.7) variant, first identified in the UK, with a reduction of 86% in hospitalizations.

The study by the British government health agency, published as pre-print on June 14, involved the AstraZeneca vaccine, produced in Brazil by Fiocruz, and the Pfizer vaccine. The study analyzed 14.019 cases of the Delta variant that arrived at the emergency rooms of English hospitals between 12 April and 4 June this year. Of these, 122 required hospitalization. The study compared the risk of hospitalization between non-vaccinated and vaccinated patients (with the first and second dose). Another 13,192 cases involving the Alpha variant were identified, with 166 hospitalizations.

The average effectiveness regarding hospitalization rates for vaccinated people with the Delta variant was similar to those of the Alpha variant, taking both vaccines into account: Alpha with 78% (one dose) and 92% (two doses); Delta with 75% and 94% (respectively).

The Pfizer vaccine presented an average of 94% of effectiveness after the first dose and 96% after the second dose, against hospitalization due to the Delta variant. AstraZeneca showed 71% effectiveness after the first dose and 92% after the second. “These findings show very high levels of protection against hospitalization due to the Delta variant with one or two doses of any of the two vaccines”, says the study.


The COVID-19 (recombinant) vaccine, the result of the partnership with AstraZeneca, was developed by the University of Oxford through the non-replicating virus technology platform (from chimpanzee adenovirus, a genetically modified adenovirus, harmless to humans, is obtained through the insertion of the gene encoding the Sars-CoV-2 virus S protein).

The vaccine received conditional authorization for trade or emergency use in more than 80 countries in six continents. More than 500 million doses were supplied to 165 countries worldwide, including more than 100 countries through the Covax Facility.

The Delta variant has contributed to the current wave of infections in India. It has recently replaced the Alpha variant as the dominant strain in Scotland and is responsible for a significant increase in the number of cases in the United Kingdom. The Strategic Advisory Group of Experts in Immunization (Sage) of the World Health Organization (WHO) has recommended the use of the AstraZeneca vaccine even in countries where variants are currently circulating. 

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