After two doses, “only modest differences” in the efficacy of the anti Covid vaccines against the Delta variant of Sars-CoV-2 compared to the Alpha variant, “more marked” after the first dose alone. This is the picture that emerges from a study conducted in Great Britain, funded by Public Health England and published in the ‘New England Journal of Medicine’, which aims to clarify the shield effect of the two most used products for prophylaxis in the country: the Pfizer / BioNTech vaccine and the AstraZeneca vaccine.
“Overall, we found high levels of efficacy of the vaccine against symptomatic disease with the Delta variant after the administration of two doses,” the authors note.
“These estimates were only slightly lower than the estimate of the efficacy of the vaccine against the Alpha variant. We found – continue the scientists of the various bodies involved in the study, from the London School of Hygiene and Tropical Medicine to Imperial College London – that the absolute difference in vaccine efficacy against symptomatic disease with one dose of vaccine with the Delta variant versus the Alpha variant was approximately 12-19 percentage points. However, the differences in vaccine efficacy after two doses were small. ”
And in conclusion “a clear effect was noted with both vaccines, with high levels of efficacy after two doses”. The number of cases and follow-up periods, the authors point out, are currently insufficient to estimate efficacy against serious illness, including hospitalization and death.