'Someone may have diabetes, but at what level the disease qualifies as a comorbid condition is something a doctor will decide upon and certify accordingly.'
As India's adolescents queue up for their Covid shots on January 3, they have only one option available right now -- Bharat Biotech-made Covaxin.
Cadila Healthcare-developed deoxyribonucleic acid (DNA) vaccine ZyCoV-D -- approved by the drug regulator for use in children aged 12 and above -- will not be used right away to vaccinate youngsters aged 15 and above, claimed sources.
Government sources indicated the National Technical Advisory Group on Immunisation in India has not recommended the use of ZyCoV-D for the time being for children below 18.
"Even after the Drugs Controller General of India approved the DNA vaccine for use in children aged 12 and above, it has been decided that the vaccine will only be used for those aged 18 and above," says a source.
"This leaves us with only one vaccine for use in adolescents aged 15 and above -- Covaxin," the source says, adding the government is going by scientific evidence and advice alone.
On Saturday, the DCGI approved the use of Covaxin for children aged 12 and above.
On October 12, the subject expert committee advising the DCGI had approved Covaxin for use in children as young as 2 years and beyond.
The DCGI, however, took its time to come up with a final consent for Covaxin, and has approved its use for 12 years and above.
Prime Minister Narendra Modi in his address to the nation on Christmas Day said a 'precaution dose' will be given to the elderly (60 years and above) with comorbidities upon furnishing a doctor's certificate.
India had listed around 20 major comorbid conditions when vaccinations began in the earlier months of 2021.
The comorbid conditions included cardiovascular diseases, diabetes, kidney ailments, cirrhosis, cancer, sickle cell anaemia, organ transplants, prolonged use of steroids or other immunosuppressant drugs.
The same set of comorbidities will be considered when evaluating if someone is eligible for an additional shot or a third shot.
"Someone may have diabetes, but at what level the disease qualifies as a comorbid condition is something a doctor will decide upon and certify accordingly," says a government source.
While registering on CoWIN, one needs to either upload the certificate of comorbidity signed by a registered doctor, or carry a printed version of it to the vaccination centre.
Children will, however, have a simple process of registration -- anyone eligible (15 years and above) will register for getting their shots.
Moreover, the gap between the third dose and the last received dose (second dose) will be seven to nine months.
The government will soon issue guidelines addressing these issues.
"Before January 10, guidelines will be issued on gaps between doses, which vaccine can be taken as a precaution dose, etc. These will be based on scientific advisory," says a government source.
Once someone is vaccinated, antibodies are generated against the pathogen, which decline after a period of time, but T-cells (or memory cells) remain active.
No major studies are there which track the T-cell response over a long period of time for the Covid vaccines available.
"However, in India five or six major studies have tracked antibodies generated by Covaxin and Covishield," says a government source in the know.
"These studies have found that unlike messenger ribonucleic acid (mRNA like Pfizer and Moderna, the rise and decline of antibodies generated by Covishield and Covaxin are not sharp enough," says a government source in the know.
Antibodies generated by Covishield and Covaxin show a gradual rise and a gradual weakening, the source points out.
"The gap or distance between the initiation of the increase and the decline is anywhere between seven and nine months and T-cells remain active even after that," says the source.
"Ideally, an additional dose or precaution shot should be given after seven to nine months after the second vaccine dose. However, in the case of Pfizer and Moderna (or mRNA vaccines), this gap is three to four months," adds the source.
The Centre is of the opinion that booster shots are population- and frequency-specific interventions.
"When we say we are giving 'boosters' to 60 years and above, it implies that the door is open to other age groups. When we say it is a precaution dose or additional dose, that door is not open," clarifies a source.
Decisions on allowing 'precaution shots' or additional shots for other age groups will be taken eventually if the need arises.
Feature Presentation: Ashish Narsale/Rediff.com