2 doses best bet against Delta: Oxford

Aditi Tandon

Tribune News Service

New Delhi, August 19

Getting two vaccine doses remains the most effective way to ensure protection against the Delta variant of concern dominant in the UK and India today and present in 148 countries, according to a study from the University of Oxford.

Published as a pre-print today, the study found that with Delta, Pfizer-BioNTech and Oxford-AstraZeneca vaccines still offered good protection against new infections, but effectiveness was reduced compared with Alpha. Researchers analysed 25,80,021 test results from over 3,80,000 participants.

People, who had been vaccinated after already being infected, had even more protection than vaccinated individuals who had not had Covid before. However, Delta infections after two vaccine doses had similar peak levels of virus to those in unvaccinated people; with the Alpha variant, peak virus levels in those infected post-vaccination were much lower.

Professor Sarah Walker of University of Oxford and Chief Investigator for the Covid-19 Infection Survey, said: “We don’t yet know how much transmission can happen from people who get Covid after being vaccinated but the fact that they can have high levels of virus suggests that people who aren’t yet vaccinated may not be as protected from the Delta variant as we hoped. This means it is essential for as many people as possible to get vaccinated — both in the UK and worldwide.”

This study from the Covid-19 Infection Survey is the largest to evaluate, and directly compare the real-world effectiveness of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines against all infections, including those without symptoms, after the Delta variant has dominated.

Combating Covid

25,80,021 test results

3,80,000 participants

90% genome sequenced cases in India are of Delta lineage

48 countries have the variant

Findings of the study

• The study concludes that a single dose of the Moderna vaccine has similar or greater effectiveness against the Delta variant as single doses of the other vaccines.
• Two doses of Pfizer-BioNTech have greater initial effectiveness against new Covid infections, but this declines faster compared with two doses of Oxford-AstraZeneca, say researchers.
• Results suggest after four to five months, effectiveness of these two vaccines will be similar, but long-term effects need to be studied.

Global cases rising for two months: WHO

• The global number of new Covid cases has been increasing for the past two months, with over 4.4 million cases reported in the past week, the WHO has said.
• The cumulative number of cases reported globally is now over 206 million and the cumulative number of deaths is almost 4.4 million.
• At the country level, the highest numbers of new cases in the past week were reported by the US (8,83,996 new cases).