2 Doses of Pfizer or Astrazeneca Vaccine Effective Against Delta COVID-19 Variant: Study

Vials with Pfizer-BioNTech and AstraZeneca COVID-19 vaccine labels are seen in this illustration picture taken March 19, 2021. Dado Ruvic/Illustration/Reuters

The Pfizer or AstraZeneca vaccines for COVID-19 are nearly as effective against the Delta variant as they are against the previously dominant Alpha variant, when the person receives two doses of the vaccine, a new study published on Wednesday suggests.

The highly contagious Delta variant, first identified in India in late 2020, is now the dominant variant of the CCP (Chinese Communist Party) virus worldwide. The CCP virus causes the disease COVID-19.

Researchers have previously said it’s too early to say whether the Delta variant is more or less deadly than other CCP virus variants. Correspondence published in The Lancet in June suggested that the chance of hospitalization may be higher with the Delta variant compared to the earlier Alpha variant.

Authors of the new study, published in the New England Journal of Medicine, reported that two doses of the Pfizer vaccine were 88 percent effective at curbing symptomatic COVID-19 from the Delta variant, compared to 93.7 percent effective against the Alpha variant.

Meanwhile, two doses of the AstraZeneca vaccine were 67 percent effective against the Delta variant and 74.5 percent effective against the Alpha variant.

“Only modest differences in vaccine effectiveness were noted with the delta variant as compared with the alpha variant after the receipt of two vaccine doses,” the authors concluded. “Absolute differences in vaccine effectiveness were more marked after the receipt of the first dose.

They added, “This finding would support efforts to maximize vaccine uptake with two doses among vulnerable populations.”

The latest study was conducted in England and was funded by Public Health England (PHE). It analyzed data of all COVID-19 vaccinations recorded in the country up until May 16, as well as all positive polymerase-chain-reaction (PCR) tests between Oct. 26, 2020, and May 16.

A previous PHE study published in May found that two doses of the Pfizer vaccine were 88 percent effective against the Delta variant and 93 percent effective against the Alpha variant—very similar to the latest study’s findings.

The May study had also found that two doses of the AstraZeneca vaccine were 60 percent effective against the Delta variant, and 66 percent effective against the Alpha variant—a slight increase. At the time, the study authors also noted that a single dose of either of the vaccines was about 33 percent effective against the Delta variant, compared to 50 percent effective for the Alpha variant.

The latest study out on Wednesday, titled “Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant,” found that one Pfizer vaccine dose was 36 percent effective, while one AstraZeneca vaccine dose was about 30 percent effective against the Delta variant.

“Overall, we found high levels of vaccine effectiveness against symptomatic disease with the delta variant after the receipt of two doses,” the study authors wrote, later adding, “Our finding of reduced effectiveness after the first dose would support efforts to maximize vaccine uptake with two doses among vulnerable groups in the context of circulation of the delta variant.”