Pfizer, AstraZeneca vaccines protect against Delta variant: Lancet study

Researchers at Public Health Scotland and the University of Edinburgh, UK, found that the Pfizer-BioNTech vaccine offered better protection against the Delta variant compared to the Oxford-AstraZeneca preventive, known as Covishield in India.

PTI
June 15, 2021 / 01:47 PM IST

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The Delta variant of coronavirus, first identified in India, doubles the risk of hospitalisation compared with the Alpha variant first found in the UK, but Pfizer and AstraZeneca vaccines provide good protection against the strain, says a study published in The Lancet journal.

Researchers at Public Health Scotland and the University of Edinburgh, UK, found that the Pfizer-BioNTech vaccine offered better protection against the Delta variant compared to the Oxford-AstraZeneca preventive, known as Covishield in India.

The analysis covered the period from April 1 to June 6, 2021, for the demographic distribution of cases.

The team analysed 19,543 confirmed SARS-CoV-2 infections over the period of interest, of whom 377 were admitted to hospital for COVID-19 in Scotland.

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

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There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

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Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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Around 7,723 community cases and 134 hospitalisations were found to have the Delta variant of coronavirus.

The study found that the Pfizer vaccine offered 92 percent protection against the Alpha variant and 79 percent against the Delta strain two weeks after the second dose.

For AstraZeneca's vaccine, there was 60 percent protection against Delta compared with 73 percent for Alpha variant, the researchers said.

They also found that two doses of vaccine provide much better protection against the Delta variant compared to a single dose.

"Risk of COVID-19 hospital admission was approximately doubled in those with the Delta variant of concern (VOC) when compared to the Alpha VOC, with risk of admission particularly increased in those with five or more relevant comorbidities,” the authors of the study noted.

"Both the Oxford–AstraZeneca and Pfizer–BioNTech COVID-19 vaccines were effective in reducing the risk of SARS-CoV-2 infection and COVID-19 hospitalisation in people with the Delta VOC," they said.

However, the researchers noted that these effects on infection with Delta variant appeared to be diminished when compared to those with the Alpha VOC.

The authors of the study warned that the vaccine comparison should be interpreted with caution due to differences in the groups which received each type of vaccine, and also in how quickly immunity is developed with each shot.

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TAGS: #AstraZeneca #coronavirus #COVID-19 vaccine #Delta variant #Health #Pfizer #The Lancet
first published: Jun 15, 2021 01:47 pm