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Covaxin supplies, trial group size — why there’s a delay in Covid vaccine for younger kids

Monthly Covaxin output between 5.5-6.5 cr. Country needs at least 15 cr doses for full coverage 15-18 age group. Choice of 6 μg dose reduced manufacturing capacity, says Bharat Biotech.

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New Delhi: Concerns about Covaxin availability and the cohort size for clinical trials on children are among the prime considerations holding back the opening up of Covid vaccination for younger age groups (those below 15 years), top government sources have told ThePrint.

Covaxin has been approved by the Drugs Controller General of India (DGCI) for use in the 12-18 years age group, based on its trial data, and is currently the only Covid vaccine that is mandated by the government to be used for those in the 15-18 year-old category, for whom vaccination has been opened.

The vaccine has also been recommended for approval in the 2-18 years category by the DGCI’s subject expert committee. Bharat Biotech in a statement Saturday said that although both the 3 and 6 μg dosages of the vaccine had been found to be immunogenic, a decision to go with the latter had “reduced manufacturing capacity by half”.

According to the latest statement from the Press Information Bureau, India has so far vaccinated 70 per cent of eligible children with one dose of the vaccine, while 24 per cent have received both doses.

Sources said Covaxin manufacturer Bharat Biotech’s “long and complicated process of vaccine manufacturing” has meant that the company is currently churning out only around 5.5 crore to 6.5 crore doses per month. To vaccinate the 7.5 crore population in the 15-18 year-old age group (estimate shared by health secretary Rajesh Bhushan in a letter to states last December) with two vaccine doses, India needs at least 15 crore doses of the vaccine.

Covaxin is also being used for precaution doses (third vaccine dose) for healthcare workers, frontline workers and senior citizens. Since India does not allow mixing of vaccines, those who have once received Covaxin shots — either for their first or second dose — can only be given the same vaccine for subsequent doses, so it is essential that sufficient stocks are maintained for that purpose too. In addition, there is a rising demand for Covaxin among those receiving their first doses, said health ministry sources.

Also read: Have PM Modi or ministers taken third shot? No word from govt a month into booster drive

‘Long and tedious manufacturing process’

When asked the reason for the delay in vaccinating younger children against Covid, a senior health ministry official, speaking on conditions of anonymity, said, “Where are the vaccines? Covaxin supplies are still in the 5-6 crore (doses per month) range. We have to ensure that we have enough for the ones that we have announced it for before opening up further vaccination and creating confusion. Also it is not as if Covaxin has stopped being used in adults.”

The official added: “We have to keep sufficient doses for the precaution shots and then there are a growing number of people asking for Covaxin when they come for their first shots. In adults about 8-10 per cent vaccines being given are of Covaxin, so that would be about two-three crore (doses) per month.”

In comparison, the Serum Institute of India-manufactured Covishield’s monthly output is currently in the 28-30 crore doses range, officials said.

Another health ministry official said that the reason the per month manufacturing figures for Covaxin varies between only 5.5- 6.5 crore, is that the manufacturing process for the vaccine is long and tedious.

“The key thing is to grow enough viruses in the lab and then to ensure that in each batch there is no live virus left. If there is even one live virus the entire batch needs to be discarded. Since the time they started upping the output, it has happened twice that the whole batch had to be discarded for this reason,” the official said. However, Bharat Biotech in its statement said that no batches had been discarded for this reason.

The company also said: “Every batch of Covaxin requires more than 250 quality control tests before it can be released for supplies. Based on company policy, vaccine industry standards and guidelines, no compromises on quality are accepted. Inactivated vaccines are highly purified, which result in a superior safety profile, but also result in lower yields.”

“The safety profile is well established with no vaccine or related adverse events of thrombocytopenia or myocarditis observed. Bharat Biotech is always focussed on safety, efficacy and quality,” it added.

It further said: “While both the 3 μg and the 6 μg dosages of Covaxin were safe and immunogenic in phase 2 clinical trials, based on sound scientific data, safety and ethics, the company had decided to proceed with the 6 μg dose, further reducing manufacturing capacity by half.”

Also read: Complex manufacturing, R&D, risks, losses — Bharat Biotech explains why Covaxin is expensive

Two vaccines approved for children younger than 15 years

Currently India has two Covid vaccines that can be administered in children younger than 15 years. While Covaxin has been recommended for use in children aged as young as two years, ZyCoV-D — manufactured by Zydus Cadila — has been approved for those aged 12 years and above. However, the consensus currently is to use ZyCoV-D only for adults. While the vaccine has started reaching Bihar (the first state to get supplies), they are yet to be used in the government’s vaccination programme. ZyCoV-D is the world’s first DNA vaccine.

“It is a completely new platform so it makes sense to see how it goes in adults before giving it to children,” said an official. Another Covid vaccine, Corbevax, manufactured by Biological E, has also been recommended for use in younger children (below 15 years), but the vaccine is yet to be delivered.

“The first batches of Corbevax should start reaching the consignee points all over the country from 20 February. The Covid working group of the National Technical Advisory Group on Immunisation (NTAGI) has looked at Covaxin and Corbevax for younger children in only one meeting. There are some concerns about the Covaxin data in younger children because the cohort of children below 15 years is really small. It will be taken up by the group in subsequent meetings and we will see what recommendations come. If Corbevax is not cleared by them for use in younger children, we may administer that too in adults,” the official said.

A Bharat Biotech statement from December on Covaxin trials in children gives an age-wise break up of the cohort. “For the trial, 976 subjects were screened for SARS-CoV-2 by RT-PCR and ELISA testing. Out of these, 525 eligible participants were enrolled. Based on the age, participants were distinguished into three groups in an age de-escalatory manner. Group I consisted of children of age 12-18 years (n=175), group II consisted of children of age 6-12 years (n=175), and group III consisted of children of age 2-6 years (n=175),” it said. The “n=175” indicates each group had 175 participants.

In Saturday’s statement, the company said, “Covaxin is the only vaccine in India to have published clinical trial data in children 2-18 years of age. These trials were conducted based on regulatory approvals by CDCSO and DCGI. Covaxin was evaluated in 175 subjects in the 12-18 years age group and 350 subjects below 12 years of age.”

Third dose concerns

Meanwhile, the question of whether or not precaution doses should be administered to all Indians regardless of their vulnerability is still being debated. A section of experts in the government feel that giving the third dose now — when the third wave is on the wane in most parts of the country — may limit India’s options for the future, especially if a newer variant arrives.

“One needs to understand how immunity works. For the vaccines we are using, the seroconversion is higher than say mRNA vaccines and the vaccine remains effective for longer. If we give a third dose now and pump up the immune system, we may not get the desired effect if another variant arrives eight-nine months from now. That is one side of the argument. We are still weighing all options and will go by the final decision,” said a senior government official.

Limiting third dose administration now may also make more Covaxin doses available for children who are yet to receive even the first two doses.

(Edited by Poulomi Banerjee)

This report has been updated to reflect the statement from Bharat Biotech dated 19 February, 2022.

Also read: What you need to know about your booster shot, and how long can it protect you


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