The study also looked at the effectiveness of booster doses at preventing infection, finding that the risk of infection was around three times lower in those who had received a third dose, compared to those who had received two.
The weekly bulletin said that AY.4.2 frequency in Indian data varies based on the definition used (PHE vs PANGO). Other than lineage-based tracking, Delta variants with immune escape mutations are also being tracked by INSACOG, some of which are also being seen by UKHSA, it added.
The outbreak of the Delta variant of Covid-19 in the southern province of Fujian has become a case of huge concern for the Chinese authorities. The number of cases is increasing at a rapid speed while the authorities are struggling to contain new infections.
Capital city Beijing reported two new COVID-19 confirmed and one asymptomatic cases on Sunday, a spokesperson said at a press briefing.
The IMF stressed the importance of vaccinations in the economic recovery from the pandemic and noted that countries like India that lagged in the rate of vaccinations would suffer if more infectious variants developed.
Delta, which was first found in India and is now in over 100 countries, represented 51.7 per cent of new infections in the US over the two weeks ending July 3.
Lower protection against B.1.351, the variant with the least sensitivity to neutralising antibodies, has been demonstrated for at least three vaccines. However, progression to severe disease and death was low in all studies.
The Delta variant, first detected in India, is likely an underestimate and the highly transmissible strain is expected to rapidly outcompete other variants and become dominant globally over the coming months, WHO said.