Why India still has a 12-16 week gap between doses of Covishield


Benaulim and Jaipur: Several countries have narrowed the gap between doses of the Oxford / AstraZeneca vaccine (branded by Covishield in India) to eight weeks in response to the emergence of the more transmissible Delta variant of SARS-CoV-2, the virus that causes Covid -19. Recent studies both in India and abroad have also shown greater effectiveness of two doses of the Oxford / AstraZeneca vaccine compared to a single dose, especially against the Delta variant. India, however, has not reduced 12 to 16 weeks dosing interval for Covishield.

Indeed, India is at a different stage of the pandemic compared to other countries using the same vaccine, experts said. IndiaSpend. The difference between the effectiveness of a single dose versus two doses is not that big for protection against hospitalization and serious illness, and India still has not given a single dose at half Population.

Before September 20, 22% of India’s eligible adult population and 15.4% of the general population were fully immunized. Covishield represents 88% of all vaccine doses administered on that date.

“When the vaccine supply is limited, it is more important to cover as many people as possible with a single dose. I think from a public health point of view this is the right strategy,” said Shahid Jameel, virologist and visiting professor at Sonepat Ashoka University.

We examine the rationale for the comparatively longer interval in India between two doses of Covishield.

What other countries using the Oxford / AstraZeneca vaccine are doing

In India, Covishield is manufactured by the Serum Institute of India on behalf of the Anglo-Swedish multinational pharmaceutical and biotechnology company AstraZeneCalifornia, and is a version of Covid-19 vaccine developed by the University of Oxford. Several countries use the same vaccine, manufactured under different names, including Vaxzevria, used in the UK and in the European Union.

On December 31, 2020, the United Kingdom’s Joint Committee on Vaccination and Immunization (JCVI) declared that a longer interval between the first and second dose of the Oxford / AstraZeneca vaccine produced a stronger immune response. They recommended a 12 week gap between the two doses.

Two weeks later, on January 16, 2021, when the Indian vaccination program was rolled out, the two-dose Covishield vaccine was to be given with an interval of four to six weeks between doses. March 22 was increase at six-eight weeks, citing scientific evidence that the increased interval provided enhanced protection. On May 13, at the height of the second wave of Covid-19, the National Technical Advisory Group on Immunization of the Covid-19 Working Group (NTAGI) advised the dosing interval of Covishield be extended from 12 to 16 weeks.

But the next day, May 14, the JCVI from the United Kingdom advised that the administration of the second dose of vaccine in the UK be brought forward by 12 to eight weeks, particularly in areas where the Delta variant was a major threat. The Delta variant is Following transmissible than any other variant to date of the Covid-19 virus, and was one of the causes of the second wave of Covid-19 in India, by to study led by the National Center for Disease Control in Delhi published in June 2021.

June 10, Northern Ireland mandated that the interval between the first and the second dose of Oxford / AstraZeneca vaccine be a maximum of eight weeks; June 13, Scotland demand all people over 40 whose second dose appointments are scheduled more than eight weeks after the first dose, to make earlier appointments; and on July 6, England’s National Health Service informed acceleration of second doses for all eligible groups “to guarantee everyone the strongest possible protection against the Delta variant of the virus as early as possible”.

Some recent studies in India, notably in Maximum number of hospitals in the National Capital Region (NCR) and Sir Ganga Ram Hospital in New Delhi, found more breakthrough infections among healthcare workers who had only received one dose of the Covishield vaccine versus two doses.

Almost half (48.4%) of the 597 healthcare workers at four Max hospitals in the NCR who had taken a single dose of the Covishield vaccine, and 25.3% of those fully vaccinated, had breakthrough infections during the Delta variant wave in the capital, the pre-print from August 2021 says. One dose of the vaccine should not be expected to offer great protection against the Delta variant, but “there were no serious infections resulting in hospitalizations,” the study found. The Max study recommended reducing the dosage interval of Covishield to six weeks.

In the to study at Sir Ganga Ram Hospital, a preprint published in the European Journal of Internal Medicine in August, a single dose of Covishield offered little protection (18%) against symptomatic Delta variant infections, which is lower than that shown by other studies, including those performed in Christian medical college (CMC), Vellore, in June (61%) and by Public health England (30%).

Against moderate to severe disease, full immunization with Covishield provided 67% protection, but those dosed only had 37% protection. Full immunization provided 76% protection against the need for oxygen therapy, but a single dose only provided 53%. According to the study conducted at Sir Ganga Ram Hospital, fully immunized people had 97% protection against death and partially vaccinated, 69%.

“Two doses are definitely better than one,” Jameel said.

Why a longer gap is suitable for India

The rationale for a longer gap between doses is based on the scientific fact that “to maximize the immune response of a vaccine, you should have as long a gap as possible”, Gagandeep Kang, virologist and professor at CMC, Vellore, said IndiaSpend.

When the gap between doses was longer, the vaccine’s effectiveness was around 90%, while in trials with a shorter gap, the effectiveness was around 60%, Jameel said. “Several studies show that even a single dose of vaccine provides decent protection against serious illness and death,” he added.

For example, the to study by CMC Vellore has shown 70% protection against hospitalization with a single dose of a Covid-19 vaccine, going up to 77% with two doses. “This study would have been essential in driving India’s policy to maximize single-dose coverage,” Jameel said. The study of 8,991 employees, vaccinated between January 21 and April 30, 2021, and published in June 2021, did not examine the variants responsible for the second wave or distinguish between Covishield and Covaxin; however, 93.4% (8,394) of staff received Covishield. The Delta variant was found in 96% of samples sequenced from Tamil Nadu in May, according to data from the Indian SARS-CoV-2 genomics consortium.

It’s also important to understand the background to the change in dosing interval in other countries, Kang said.

When the UK announced the reduction from 12 weeks to eight weeks, it noted that this advice was “specific to the circumstances in the UK at that time” and was “only possible because everyone in the priority groups of phase 1 [including the elderly and those with comorbidities] has already been offered a first dose “. more prone to severe Covid-19 and are at higher risk of death.

Likewise, when Scotland reduced the dose gap to eight weeks, it had vaccinated more than three quarters of the adult population with a single dose and more than half of the population were fully vaccinated. “We remain on track to deliver the vaccine to all adults by the end of July,” the Scottish government said. noted June 13.

On the other hand, 22% of India’s eligible adult population and 15% of the general population were fully immunized and 43% of adults had received a dose by September 20. “In India, we are still at a stage where around 65% of those over 60 have only received a single dose of vaccination. not good enough, ”Kang said.

Demand better data from India

The Indian studies referenced above were carried out in health facilities and therefore include a much lower proportion of the population than countries which have good quality data for larger populations. For example, the study in Max hospitals included 597 people, while the England Public Health Study, published in August 2021, included 19,000 people. “The smaller the study sample, the greater the variation in the results,” Kang said.

“At the end of the day what we should have is data on the people of our country – we have administered more doses of the AstraZeneca or Covaxin vaccine than anyone in the world and yet we are generating data from hospitals because that healthcare workers are a captive population, ”Kang added, stressing the need for better data from India.

A single dose of a Covid-19 vaccine in India has been 96.6% efficient in the prevention of mortality, and two doses were 97.5% effective, said Balram Bhargava, director general of the Indian Council of Medical Research (ICMR), India’s supreme scientific body, during a press conference. press conference September 9. This claim was based on data from the ICMR on Covid-19 cases from April 18 to August 15, but no further details or data were provided, including how many infections were pierced, or at what vaccine data is linked.

Reduce the gap for certain vulnerable populations

India had reduced the dosage interval of Covishield to as little as four weeks for people traveling abroad, including students and athletes participating in the Olympic Games.

If India were to consider reducing the dosing interval for Covishield, it should first do so for the population that is more prone to serious illness or death from Covid-19 or where there are currently more than cases of Covid-19, experts said.

“If you had to think of a short gap, I’m not particularly worried about an 18 year old who wants to travel overseas. I’m worried about the 70 year old who got a dose and has hard to get the next one, “Kang said. To shorten the interval,” I would start with the people most vulnerable to serious illnesses. It would be people aged 60 and over and those with existing co-morbidities, Jameel agreed.

Additionally, “with better supplies and reduced daily infections, this would be a good time to assess the evidence and possibly narrow the gap to 8-12 weeks,” Jameel said. India administered around 9.2 million doses per day in the week to September 20, up from 8 million the week before. He must increase that figure to 10.5 million doses per day to meet his goal of vaccinating all adult Indians by the end of this year, according to our calculations.

“The decision would be based on a risk-benefit analysis of how much disease you would relieve, for which age group and in which location,” because there is a trade-off between two doses for some people versus doses unique for most people, Kang said.

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