Pfizer, AstraZeneca vaccines effective against Delta

July 22, 2021 – The Pfizer and AstraZeneca vaccines – the primary vaccine options in the UK – were less effective against Delta variant of coronavirus compared to the Alpha variant (known as B.1.1.7), according to a study published online Wednesday in the New England Journal of Medicine.

Researchers, led by Jamie Lopez Bernal, PhD, of Public Health England, write that the lower effectiveness against the Delta variant is especially evident after a single dose, but even after two doses they were less effective. Yet the Pfizer vaccine was at least 88% effective against Delta after two doses; the AstraZeneca vaccine was 67% effective.

The differences were particularly noticeable after a single dose of either vaccine. With one dose of Pfizer, the efficacy against the Alpha variant was 48.7% versus 30.7% against the Delta variant. Results after one dose of AstraZeneca vaccine were similar.

The Delta variant first appeared in India, but has quickly spread globally and is now fueling an increase in COVID cases in countries like the UK. In the United States, the Delta variant now represents at least 83% of cases.

“The fact [that] there is still a noticeable efficiency is encouraging. However, complacency is not warranted, as the virus will continue to cause at least mild illness, even in some cases. [of] those vaccinated with two doses, ”said Stephen JW Evans, epidemiologist at the London School of Hygiene & Tropical Medicine (UK.