Full two-dose vaccination halves Delta transmission and is 60% effective in preventing symptomatic Covid-19 due to the same variant of the coronavirus, according to long-term British scientific research React-1.
The study by Imperial College London, which analyzed data from around 98.000 people in England, provides the most comprehensive picture to date of how well vaccines protect against the most contagious Delta ("Indian"), which has replaced Alpha ("British") as the dominant variant.
The ongoing React-1 (Real-time Assessment of Community Transmission) study, which began last April, provides a monthly picture of the pandemic by testing a random large sample of people. The new React study, according to the Financial Times, found that 40% of those diagnosed with coronavirus (all with Delta) were asymptomatic, while many others had mild symptoms.
Other recent research has shown that 90% of Delta vaccines are effective in treating severe symptoms and avoiding hospitalization. The lower efficacy of 60% of Delta vaccines found by React-1 explains why the British study included the ability of vaccines to prevent even the least severe symptoms, not just the serious ones and the need for hospitalization.
"The vaccine remains highly effective against Delta," said Dr. Paul Eliot of Imperial, whose study did not provide detailed data on the separate efficacy of the Pfizer and AstraZeneca vaccines.
"The findings, when combined with those of other studies showing the impact of coronavirus vaccines on the reduction of hospitalizations and deaths from Covid-19, are encouraging. But they are also a reminder that, even with very high vaccination coverage, it is very likely that we will have another wave of infections in the fall, "said Dr Tom Wingfield of the Liverpool School of Tropical Medicine.
Source: RES-EAP