To combat the delta variant of Covid, extend the second dose of protection as soon as possible: learn

Delta has been declared a Variant of Concern (VOC) by the World Health Organization (WHO). First discovered in India, the delta variant is now dominant in the UK. It has replaced the B.1.1.7 (alpha) 2 strain, which emerged in the UK with the second wave of Covid in late 2020.

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The study said the effectiveness of the Covid vaccine against B.1,617.2 was unknown, so they conducted a preliminary analysis to follow the serological response to vaccination.

The study was conducted using Pfizer BioNTech vaccines against five types of Covid, including the variants of concern B.1.617.2 (Delta) and B.1.351 (Beta), which were first discovered in South Africa. The other three variants are: the strain with the original spike sequence (wild type); a strain with the Asp614Gly mutation isolated during the first wave of infection in the UK (D614G); and B.1.1.7 (alpha).

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The study found that two doses of Pfizer vaccine elicited “ELISA-approved anti-wild-type spike antibodies” and neutralizing antibodies for all strains, including three VOCs, in all participants. However, six (3%) and nine (5%) of the 159 participants did not have antibodies to B.1.617.2 and B.1.351, respectively.

The study also compared the effectiveness of the vaccine between the two doses.

The study found that the neutralizing variant of concern was “significantly different” after just one dose of Pfizer vaccine. It also said that most participants who received two doses of Pfizer vaccine “would be protected against B.1,617.2 infection”.

“In the case of two doses of BNT162b2 (Pfizer), our generally healthy, relatively young, recently vaccinated, and mostly ethnic group, represents a plausible best-case scenario for NAb (neutralizing antibody) activity against the SARS-CoV-2 variant” , the study states. However, he added that despite the absolute requirement for vaccine effectiveness, “the peak NAbTs (NAb titer) compared with the VOCs of B.1.617.2 and B.1.351 compared to NAbTs was significantly reduced compared to the previous variant”.

In the case of single-dose recipients, the study found, data showed that NAbT was significantly lower for the delta and beta variants compared to alpha. “Single-dose recipients tend to be less protected against this SARS-CoV-2 variant,” he said.

“Therefore, these data suggest that the benefits of delaying the second dose in terms of wider population coverage and the increase in individual NAbT after the second dose now associated with the prevalence of B. must be weighed against a short-term reduction in effectiveness of .1,617.2,” the study said. .

Previously, the UK had extended the interval between the two doses to maximize population coverage.

The study said the data underscore the need to increase vaccine supplies so that all countries can “extend second-dose protection as soon as possible”.

On May 13, India extended the gap between the first and second doses of the Covishield vaccine produced by the Serum Institute to 12-16 weeks. The gap used to be 6-8 weeks.