New Delhi: A study published in the medical journal Lancet found that the antibody response to variants is lower in people who have received just one dose and a longer gap between doses may significantly reduce antibodies against the Delta variant which is dominant in India.
The study also found that the Pfizer vaccine has shown to be much effective against the Delta variant compared to the original strain of the novel coronavirus.
The Delta variant which was first detected in India resulted in the most destructive second wave. While the country still battles Covid cases, the Delta variant has spread to various countries including the UK. Delta has been declared as a Variant of Concern (VOC) by the World Health Organisation (WHO).
The study was conducted using Pfizer–BioNTech vaccine against five Covid strains, including variants of concerns B.1.617.2 (Delta) and B.1.351 (Beta) first detected in South Africa). The other three variants were: 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).
After a single dose of Pfizer, 79 percent of people had a quantifiable neutralizing antibody response against the original strain, but this fell to 50 percent for B.1.1.7 or Alpha variant, 32 percent for Delta, and 25 percent for the B.1.351 or Beta variant.
The study also compared the vaccine efficacy between the two doses.
"In the case of two BNT162b2 (Pfizer) doses, our cohort of generally healthy, relatively young, recently vaccinated, and mostly single-ethnicity individuals present a reasonable best-case scenario for NAb (neutralizing antibodies) activity against SARS-CoV-2 variants," the study said. It, however, added that regardless of the absolute vaccine efficacy requirements, "peak NAbTs (NAb titers) are significantly reduced against VOCs B.1.617.2 and B.1.351 compared with NAbTs against earlier variants".
"Single-dose recipients are likely to be less protected against these SARS-CoV-2 variants," it said.
"These data, therefore, suggest that the benefits of delaying the second dose, in terms of wider population coverage and increased individual NAbTs after the second dose, must now be weighed against decreased efficacy in the short-term, in the context of the spread of B.1.617.2," the study said.
The vaccine produces fewer antibodies with increasing age and the levels decline over time, Lancet says.
The study also welcomed the UK's plan to reduce the gap between doses as it was found that after just one dose of the Pfizer-BioNTech vaccine, people were less likely to develop antibody levels against the Delta variant.