A new study shows that two doses of the COVID-19 vaccines from Pfizer-BioNTech or AstraZeneca-Oxford are nearly as effective against the highly contagious delta coronavirus variant as they are against the previously dominant alpha variant.
Officials say the vaccines are highly effective against the delta variant, which is now the dominant variant worldwide – although the study reiterated that a single dose of the vaccines is not enough to provide high protection.
studying, Published in the New England Journal of Medicine on Wednesday, confirms key findings that Public Health England (PHE) presented in May on the efficacy of COVID-19 vaccines produced by Pfizer-BioNTech and Oxford-AstraZeneca, based on data from the real world.
The research team found that two doses of Pfizer were 88 percent effective in preventing disease symptoms from the delta variant, compared to 93.7 percent effective against the alpha variant, broadly the same as previously reported.
Two shots of the AstraZeneca vaccine were 67 percent effective against the delta variant, up from 60 percent originally reported, and 74.5 percent effective against the alpha variant, compared to the original estimate of 66 percent effectiveness.
“Only small differences in vaccine efficacy were observed with the delta variant compared to the alpha variant after receiving two doses of the vaccine,” the PHE researchers wrote in the study.
The research has not looked at the effectiveness of mixing brands of different doses, although ongoing research in the UK has shown that the Pfizer-BioNTech and AstraZeneca-Oxford vaccine appears to generate a stronger immune response than getting two rounds of an AstraZeneca dose.
Watch | The World Health Organization says:
High protection from severe diseases
Data from Israel estimated a lower efficacy of Pfizer against symptomatic disease, although protection against severe disease remains high.
PHE had previously said that the first dose of any vaccine was about 33 percent effective against disease symptoms from the delta variant.
The full study also found that a single dose of Pfizer’s vaccine was 36 percent effective, and a single dose of the AstraZeneca vaccine was 30 percent effective.
“Our finding of reduced efficacy after the first dose will support efforts to maximize two-dose vaccine uptake among vulnerable groups in the context of variable delta circulation,” the study authors said.
‘All the signs’ indicate that Delta is in charge
Hamilton immunologist Matthew Miller, a professor at McMaster University and a member of the school’s Immunology Research Center, called the study “a powerful one.”
“I think it’s really important, especially in the Canadian context right now, because all the signs are that Delta is quickly taking its place as the main rolling alternative,” he added.
Miller also noted that the high level of efficacy of two vaccines in the study, both of which were used in Canada, is a good sign for the country moving forward.
“If we can continue our momentum and get second doses of people as we go through the end of July and August, we are really setting ourselves up for success in the fall and winter where, by necessity, people have to be more home,” he said.