Two doses of the Pfizer or AstraZeneca vaccine COVID-19 are about as effective against the delta variant strain of the new coronavirus, which is highly contagious as it was against the previous dominant alpha variant, according to a study published yesterday.
Officials say the vaccines are highly effective against the delta variant strain, which has now become the dominant variant worldwide. However, the same study points out that just one dose of vaccine is not enough for high protection.
The study, published in the New England Health Inspectorate, confirms the findings, which were briefly published in May by the Public Health System of England on the effectiveness of vaccines against COVID-19 Pfizer-BioNTech and Oxford-AstraZeneca based on real-time data.
Yesterday's research found that two doses of the Pfizer vaccine were 88% effective in preventing the disease with symptoms from the Delta strain, compared with 93,7% against the Alpha strain, with the data being in broad lines about the same as those previously published.
Both doses of the AstraZeneca vaccine are 67% effective against the Delta variant, with this percentage being increased by the 60% protection initially reported. The same vaccine is 74,5% effective against the variant Alpha strain, compared to the initial estimate of 66% efficacy.
"Only limited differences in vaccine efficacy were found for the Delta variant strain compared to the alpha variant strain after receiving two doses of the vaccine," the UK Health System researchers wrote in the same study.
Data from Israel have shown that the Pfizer vaccine is less effective against symptomatic illness, although protection against severe symptoms remains high. The UK Health System has previously announced that the first dose of any of these two vaccines is approximately 33% effective against the disease with symptoms from the delta strain.
The full study published yesterday found that one dose of the Pfizer vaccine is 36% effective, while one dose of the AstraZeneca vaccine is about 30% effective. "Our findings on reduced efficacy after the first dose will support efforts to optimize the intake of two doses among vulnerable groups within the transmissibility of the Delta variant strain," according to the study participants.