To what extent do COVID-19 vaccines protect against the delta variant, according to the best available data

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To what extent do COVID-19 vaccines protect against the delta variant, according to the best available data

A nurse at Royal Cornwall Hospital prepares to give a COVID-19 vaccine in Truro, UK. Hugh Hastings / Getty Images

  • The delta variant is the most common cause of new COVID-19 infections in the US, UK and elsewhere.

  • Delta has mutations that can help it evade an immune response.

  • Four studies indicate that vaccines from Pfizer, Moderna and AstraZeneca work against Delta, to varying degrees.

  • See more stories on the Business Insider صفحة page.

The highly contagious The coronavirus delta variant causes a Increase in COVID-19 cases around the world, from the United States to India. The variant contains mutations that partially help it escape the immune response produced by vaccines.

Data on how effective COVID-19 vaccines are against the delta variant are not entirely clear.

World Health Organization Tuesday saidOn July 6, the COVID-19 vaccines from Pfizer-BioNTech and AstraZeneca worked well against the severe COVID-19 caused by Delta, compared to the other variants. Vaccines may offer less protection against symptomatic – rather than severe – diseases caused by Delta than other types, she added.

Here’s how much protection the COVID-19 vaccines can give you against symptomatic delta infection, based on the best available data from four studies.

Study in the UKPfizer 88% effective, AstraZeneca 60%

A UK study from May found that two doses of AstraZeneca or Pfizer’s vaccine were very effective against the delta variant, two weeks after the second dose.



Canadian studyPfizer 87% effective after 2 doses, Moderna 72% effective after 1 dose

Canadian study Spread On Saturday, July 3, two doses of the COVID-19 vaccine were found to work as well against delta as they did against the alpha variant, which was previously prevalent in the United States.

The study has not been examined by peer-reviewed experts.




Israel a studyPfizer 64% effective after two doses

The Israeli Ministry of Health said on Monday 6th JulyHowever, the Pfizer vaccine performed slightly less well against the delta variant than previously estimated. The number of people who became infected during the study period was small, and the number may include asymptomatic infections.


Study ScotlandPfizer: 79% effective after 2 doses and 60% effective for AstraZeneca.

Scotland-based study published as a letter to the Lancet medical journal On June 14 It found that the Pfizer vaccine provides “very good” protection against the delta variant.



Why are the numbers different?

Vaccine efficacy percentage is the percentage of people who receive complete protection after a vaccine. With up to 80% efficacy, 80% of people have full protection, 20% don’t.

It becomes difficult to gauge the quality of vaccines Work in the real world Compared to experiments, because you can’t control who gets vaccinated and who isn’t. Other differences between the two groups could affect the risk of getting sick from COVID-19. For example, those who choose not to be vaccinated could be more likely to put themselves in risky situations that could expose them to the virus.

The numbers can also vary because they depend on many factors, including what you’re measuring, when you’re measuring it, the age of the population you’re measuring in, and whether there have been previous COVID-19 infections.

Stephen Evans, professor of medical statistics at the London School of Hygiene and Tropical Medicine, told Insider that in general, the more severe the disease Delta causes, the better the COVID-19 vaccines seemed to work against it. But he said the evidence for the effectiveness of vaccines was not strong.

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