Covid-19: Is the Pfizer vaccine effective against the Delta variant?

Variants of the coronavirus like Delta and Delta Plus may have raised concerns about the effectiveness of vaccines, but Pfizer says its two-dose vaccine remains potent against these new variants.

The company, meanwhile, is conducting trials on a third dose to understand efficacy beyond six months and enhanced immunity in populations.

“We are monitoring trial participants from our landmark Covid-19 vaccine study for two years after their second dose to learn more about the vaccine’s protection against this disease, and to be as prepared as possible,” said Dr Yasser El Dershaby, Pfizer’s Africa & Middle East Regional Medical Affairs Lead.

Viruses evolve and mutate naturally, and these variations are tracked by scientists through genomic sequencing by which the genes of the pathogen are studied.

The Sars-Cov-2 coronavirus has mutated into four variants -- Alpha, Beta, Gamma and Delta, with Delta being the most transmissible. It’s already the most dominant strain in the US, while 33 per cent of Covid-19 infections in the UAE are caused by it. The Delta Plus variant is also evoking interest and concerns in India.

Studies initially showed Pfizer's vaccine offered 94 per cent protection after two doses against early variants. However, it slips to 90 per cent against the Delta, which is still good to prevent serious moderate and serious infection that could lead to hospitalisation.

Prototype vaccine against future variants

The company is also studying a booster dose and a prototype vaccine with a ‘variant sequence’ for use against strains that might emerge in the future.

This study evaluates the safety and immunogenicity of a third dose to understand the effect of a booster on immunity against Covid-19 caused by the circulating and emerging Sars-CoV-2 variants

This is part of Pfizer’s and BioNTech’s broad development programme that may equip the companies with the “science needed to address 'emerging variants of concern'. The latest Delta Plus found in India could fall into that category. So, should we worry? The speed of mutations within 18 months of the first cases in Wuhan, China, is indeed a matter of concern but as viruses mutate and spread rapidly, they also tend to weaken.

“To date, we are encouraged by both the real-world data and laboratory studies of the vaccine and see no evidence that the virus or circulating variants of concern regularly escape protection,” Dr El Dershaby said.

We will have to live with it

As part of the plan, the United States will allocate the vaccines, free-of-charge, to 92 low and lower middle-income countries and economies. The US government will work with COVAX, the global vaccine alliance, to ensure efficient and equitable deliveries of the jabs.