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Pharma wrap: Why India should consider extension of interval between two doses of Covishield vaccine

"In exploratory analyses, a single standard dose of ChAdOx1 nCoV-19 had an efficacy of 76 percent against symptomatic COVD-19 in the first 90 days after vaccination, with no significant waning of protection during this period," Lancet study said.

February 21, 2021 / 10:54 AM IST
Representative image: Reuters

Representative image: Reuters


Even as Indian government’s panel of experts is reviewing whether to extend the gap between two doses of the AstraZeneca- Oxford vaccine from four weeks to 8-12 weeks, a new study published in British medical journal Lancet says that a 12-week or three-month interval before the second dose provides better protection.

"In exploratory analyses, a single standard dose of ChAdOx1 nCoV-19 had an efficacy of 76 percent against symptomatic COVD-19 in the first 90 days after vaccination, with no significant waning of protection during this period," Lancet study said.

The study pointed out that the vaccine efficacy after the second dose was even higher at 81·3 percent in those with a dosing interval of 12 weeks or more versus 55·1 percent in those with an interval of less than six weeks.

The study is based on the combined data from clinical trials in the UK, Brazil, and South Africa, which together included a total of 17,178 adult participants.

WHO has already recommended an interval of eight to 12 weeks between doses.

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COVID-19 Vaccine

Frequently Asked Questions

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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.

How many types of vaccines are there?

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.

What does it take to develop a vaccine of this kind?

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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In India, AstraZeneca- Oxford vaccine - manufactured and distributed by Serum Institute of India (SII) under brand name Covishield - was approved for restricted emergency use by Drug Controller General of India (DCGI) with a recommendation of the four to six weeks interval between doses. Covishield’s vaccination course consists of two separate doses of 0.5 ml each. It is recommended that individuals who receive the first dose of Covishield should complete the vaccination course with the second one. The Phase 2/3 bridge trial that SII did for Covishield followed the dosing regimen of two full doses with 4 weeks interval.

Please read here to know about SII's Covishield's package insert factsheet.

Why India should consider this evidence

The extension of interval between the two doses, would certainly help in expansion vaccination coverage faster. India so far

India’s COVID-19 vaccination, which started on January 16, has so far inoculated about 1.8 million of healthcare and frontline workers. Around 8,73,940 people have received the second dose or booster. The numbers look impressive, but considering India's population of 1.3 billion, we haven't yet covered even 1 percent. There is still a long way to go. India needs to scale up vaccination efforts, as cases once again started to rise, to protect the vulnerable population of healthcare, frontline workers, elderly and people with comorbidities.

The other advantage is that the longer interval will help in expanding coverage even as supplies are scarce in the short term.

To be sure, it is still not fully understood whether the vaccine will prevent the human-to-human transmission of SARS-CoV-2, but much of the trial data makes it clear that the vaccine can prevent severe COVID-19 infection, and this will reduce deaths. So use of face masks, physical distancing and hand hygiene along COVID-19 vaccination will be the optimal strategy to help contain the pandemic.
Viswanath Pilla is a business journalist with 14 years of reporting experience. Based in Mumbai, Pilla covers pharma, healthcare and infrastructure sectors for Moneycontrol.
first published: Feb 21, 2021 10:54 am

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