A new study in the Lancet journal has found that the Pfizer-BioNTech’s vaccine isn’t as effective against the Delta variant, first detected in India (B.1.617.2), and needs two doses to offer any protection.
The antibody response to the Delta variant is lower in people who have received just one dose and a longer gap between doses may significantly reduce antibodies against this variant, the study said.
Lancet said the Pfizer vaccine produces five times fewer antibodies against the Delta variant compared to those against the original COVID-19 strain. The vaccine produces fewer antibodies with increasing age and the levels decline over time, Lancet says.
The Delta variant is now spreading in the UK and early evidence suggests there may be an "increased risk of hospitalisation" with the Delta strain compared to the Alpha and the Lancet study supports the UK's plans to reduce the gap between the two doses of the vaccine.
According to a report in Live Mint, the Lancet study used the Pfizer–BioNTech vaccine against five COVID-19 strains. The variants used were B.1.617.2 (Delta) and B.1.351 (Beta), first detected in South Africa.
Apart from these two, a strain with the original spike sequence (Wild-type); a strain with an Asp614Gly mutation isolated during the first wave of infection in the UK (D614G); and B.1.1.7 (Alpha) was also investigated.
The study also compared how efficient is the vaccine between two doses with the benefits of delaying the second dose (like in the UK and India) and increased individual Neutralizing antibodies (NAbTs). Flagging this as an issue, the study has said, the time delay between two doses should be brought down as the Delta strain is now rapidly spreading.